Release 6.0.0-rc.2

* Start splitting apart reconciler, with tests

* Reify children in reify

* Baseline hydrate implementation

* Remove debug print

* Scaffold out diff implementation, just supporting name changes

* invariant -> error in decodeValue

* Flesh out diff and add getProperty

* Clear out top-level reconciler interface, start updating code that touches it

* Address review feedback

* Add (experimental) Selene configuration

* Add emptiness checks to PatchSet, remove unimplement invert method

* Improve descendant destruction behavior in InstanceMap

* Track instanceId on all reify errors

* Base implementation of applyPatch, returning partial patches on failure

* Change reify to accept InstanceMap and insert instances into it

* Start testing applyPatch for removals

* Add test for applyPatch adding instances successfully and not

* Add , which is just error with formatting

* Correctly use new diff and applyPatch APIs

* Improve applyPatch logging and fix field name typo

* Better debug output when reify fails

* Print out unapplied patch in debug mode

* Don't write properties if their values are not different.

This was exposed trying to sync the Rojo plugin, which
has a gigantic ModuleScript in it with the reflection
database. This workaround was present in some form in
many versions of Rojo, and I guess we still need it.

This time, I actually documented why it's here so that
I don't forget for the umpteenth time...

* Add placeholder test that needs to happen still

* Introduce easier plugin testing, write applyPatch properties test

* Delete legacy get/setCanonicalProperty files

* Fix trying to remove numbers instead of instances

* Change applyPatch to return partial patches instead of binary success

* Work towards being able to decode and apply refs

* Add helpers for PatchSet assertions

* Apply refs in reify, test all cases

* Improve diagnostics when patches fail to apply

* Stop logging when destroying untracked instances, it's ok

* Remove read before setting property in applyPatch

* Fix diff thinking all properties are changed

.github/workflows/ci.yml

@@ -1,6 +1,13 @@
 name: CI
 
-on: [push]
+on:
+  push:
+    branches:
+    - master
+
+  pull_request:
+    branches:
+    - master
 
 jobs:
   build:
@@ -9,10 +16,12 @@ jobs:
 
     strategy:
       matrix:
-        rust_version: [stable, "1.40.0"]
+        rust_version: [stable, "1.43.1"]
 
     steps:
     - uses: actions/checkout@v1
+      with:
+        submodules: true
 
     - name: Setup Rust toolchain
       run: rustup default ${{ matrix.rust_version }}
@@ -27,10 +36,4 @@ jobs:
       run: |
         cargo fmt -- --check
         cargo clippy
-      if: matrix.rust_version == 'stable'
-
-    - name: Build (All Features)
-      run: cargo build --locked --verbose --all-features
-
-    - name: Run tests (All Features)
-      run: cargo test --locked --verbose --all-features
+      if: matrix.rust_version == 'stable'

.github/workflows/release.yml

@@ -10,6 +10,8 @@ jobs:
 
     steps:
     - uses: actions/checkout@v1
+      with:
+        submodules: true
 
     - name: Build release binary
       run: cargo build --verbose --locked --release
@@ -25,6 +27,8 @@ jobs:
 
     steps:
     - uses: actions/checkout@v1
+      with:
+        submodules: true
 
     - name: Install Rust
       run: curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
@@ -47,6 +51,8 @@ jobs:
 
     steps:
     - uses: actions/checkout@v1
+      with:
+        submodules: true
 
     - name: Build
       run: cargo build --locked --verbose --release

.gitignore

@@ -10,9 +10,15 @@
 /*.rbxl
 /*.rbxlx
 
+# Test places for the Roblox Studio Plugin
+/plugin/*.rbxlx
+
 # Roblox Studio holds 'lock' files on places
 *.rbxl.lock
 *.rbxlx.lock
 
 # Snapshot files from the 'insta' Rust crate
-**/*.snap.new
+**/*.snap.new
+
+# Selene generates a roblox.toml file that should not be checked in.
+/roblox.toml

.gitmodules

@@ -9,7 +9,4 @@
 	url = https://github.com/LPGhatguy/roblox-lua-promise.git
 [submodule "plugin/modules/t"]
 	path = plugin/modules/t
-	url = https://github.com/osyrisrblx/t.git
-[submodule "plugin/modules/rbx-dom"]
-	path = plugin/modules/rbx-dom
-	url = http://github.com/rojo-rbx/rbx-dom
+	url = https://github.com/osyrisrblx/t.git

.luacheckrc

@@ -33,7 +33,7 @@ stds.plugin = {
 stds.testez = {
 	read_globals = {
 		"describe",
-		"it", "itFOCUS", "itSKIP",
+		"it", "itFOCUS", "itSKIP", "itFIXME",
 		"FOCUS", "SKIP", "HACK_NO_XPCALL",
 		"expect",
 	}

CHANGELOG.md

@@ -1,6 +1,31 @@
 # Rojo Changelog
 
-## Unreleased Changes for 0.6.x
+## Unreleased Changes
+
+## [6.0.0 Release Candidate 2](https://github.com/rojo-rbx/rojo/releases/tag/v6.0.0-rc.1) (November 19, 2020)
+* Fixed crash when malformed CSV files are put into a project. ([#310](https://github.com/rojo-rbx/rojo/issues/310))
+* Fixed incorrect string escaping when producing Lua code from JSON files. ([#314](https://github.com/rojo-rbx/rojo/issues/314))
+* Fixed performance issues introduced in Rojo 6.0.0-rc.1. ([#317](https://github.com/rojo-rbx/rojo/issues/317))
+* Fixed `rojo plugin install` subcommand failing for everyone except Rojo developers. ([#320](https://github.com/rojo-rbx/rojo/issues/320))
+* Updated default place template to take advantage of [#210](https://github.com/rojo-rbx/rojo/pull/210).
+* Enabled glob ignore patterns by default and removed the `unstable_glob_ignore` feature.
+    * `globIgnorePaths` can be set on a project to a list of globs to ignore.
+* The Rojo plugin now completes as much as it can from a patch without disconnecting. Warnings are shown in the console.
+* Fixed 6.0.0-rc.1 regression causing instances that changed ClassName to instead... not change ClassName.
+
+## [6.0.0 Release Candidate 1](https://github.com/rojo-rbx/rojo/releases/tag/v6.0.0-rc.1) (March 29, 2020)
+This release jumped from 0.6.0 to 6.0.0. Rojo has been in use in production for many users for quite a long times, and so 6.0 is a more accurate reflection of Rojo's version than a pre-1.0 version.
+
+* Added basic settings panel to plugin, with two settings:
+    * "Open Scripts Externally": When enabled, opening a script in Studio will instead open it in your default text editor.
+    * "Two-Way Sync": When enabled, Rojo will attempt to save changes to your place back to the filesystem. **Very early feature, very broken, beware!**
+* Added `--color` option to force-enable or force-disable color in Rojo's output.
+* Added support for turning `.json` files into `ModuleScript` instances ([#308](https://github.com/rojo-rbx/rojo/pull/308))
+* Added `rojo plugin install` and `rojo plugin uninstall` to allow Rojo to manage its Roblox Studio plugin. ([#304](https://github.com/rojo-rbx/rojo/pull/304))
+* Class names no longer need to be specified for Roblox services in Rojo projects. ([#210](https://github.com/rojo-rbx/rojo/pull/210))
+* The server half of **experimental** two-way sync is now enabled by default.
+* Increased default logging verbosity in commands like `rojo build`.
+* Rojo now requires a project file again, just like 0.5.4.
 
 ## [0.6.0 Alpha 3](https://github.com/rojo-rbx/rojo/releases/tag/v0.6.0-alpha.3) (March 13, 2020)
 * Added `--watch` argument to `rojo build`. ([#284](https://github.com/rojo-rbx/rojo/pull/284))
@@ -108,7 +133,7 @@ This is a general maintenance release for the Rojo 0.5.x release series.
 
 ## [0.5.0 Alpha 9](https://github.com/rojo-rbx/rojo/releases/tag/v0.5.0-alpha.9) (April 4, 2019)
 * Changed `rojo build` to use buffered I/O, which can make it up to 2x faster in some cases.
-    * Building [*Road Not Taken*](https://github.com/rojo-rbx/roads) to an `rbxlx` file dropped from 150ms to 70ms on my machine
+    * Building [*Road Not Taken*](https://github.com/LPGhatguy/roads) to an `rbxlx` file dropped from 150ms to 70ms on my machine
 * Fixed `LocalizationTable` instances being made from `csv` files incorrectly interpreting empty rows and columns. ([#149](https://github.com/rojo-rbx/rojo/pull/149))
 * Fixed CSV files with entries that parse as numbers causing Rojo to panic. ([#152](https://github.com/rojo-rbx/rojo/pull/152))
 * Improved error messages when malformed CSV files are found in a Rojo project.
@@ -305,4 +330,4 @@ This is a general maintenance release for the Rojo 0.5.x release series.
 * More robust syncing with a new reconciler
 
 ## [0.1.0](https://github.com/rojo-rbx/rojo/releases/tag/v0.1.0) (November 29, 2017)
-* Initial release, functionally very similar to [rbxfs](https://github.com/rojo-rbx/rbxfs)
+* Initial release, functionally very similar to [rbxfs](https://github.com/LPGhatguy/rbxfs)

CONTRIBUTING.md

@@ -1,5 +1,5 @@
 # Contributing to the Rojo Project
-Rojo is a big project and can always use more help! This guide covers all repositories underneath the [rojo-rbx organization on GitHub](https://github.com/rojo-rbx).
+Rojo is a big project and can always use more help!
 
 Some of the repositories covered are:
 
@@ -15,8 +15,7 @@ You'll want these tools to work on Rojo:
 
 * Latest stable Rust compiler
 * Latest stable [Rojo](https://github.com/rojo-rbx/rojo)
-* Latest stable [Remodel](https://github.com/rojo-rbx/remodel)
-* Latest stable [run-in-roblox](https://github.com/rojo-rbx/run-in-roblox)
+* [Foreman](https://github.com/Roblox/foreman)
 
 ## Documentation
 Documentation impacts way more people than the individual lines of code we write.
@@ -33,15 +32,13 @@ Please file issues and we'll try to help figure out what the best way forward is
 ## Pushing a Rojo Release
 The Rojo release process is pretty manual right now. If you need to do it, here's how:
 
-1. Bump server version in [`server/Cargo.toml`](server/Cargo.toml)
+1. Bump server version in [`Cargo.toml`](Cargo.toml)
 2. Bump plugin version in [`plugin/src/Config.lua`](plugin/src/Config.lua)
 3. Run `cargo test` to update `Cargo.lock` and double-check tests
 4. Update [`CHANGELOG.md`](CHANGELOG.md)
 5. Commit!
     * `git add . && git commit -m "Release vX.Y.Z"`
 6. Tag the commit with the version from `Cargo.toml` prepended with a v, like `v0.4.13`
-7. Build Windows release build of CLI
-    * `cargo build --release`
 7. Publish the CLI
     * `cargo publish`
 8. Build and upload the plugin
@@ -52,4 +49,5 @@ The Rojo release process is pretty manual right now. If you need to do it, here'
 10. Copy GitHub release content from previous release
     * Update the leading text with a summary about the release
     * Paste the changelog notes (as-is!) from [`CHANGELOG.md`](CHANGELOG.md)
-    * Write a small summary of each major feature
+    * Write a small summary of each major feature
+    * Attach release artifacts from GitHub Actions for each platform

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rojo"
-version = "0.6.0-alpha.3"
+version = "6.0.0-rc.2"
 authors = ["Lucien Greathouse <me@lpghatguy.com>"]
 description = "Enables professional-grade development tools for Roblox developers"
 license = "MPL-2.0"
@@ -11,7 +11,6 @@ readme = "README.md"
 edition = "2018"
 
 exclude = [
-    "/plugin/**",
     "/test-projects/**",
 ]
 
@@ -24,18 +23,11 @@ panic = "abort"
 [features]
 default = []
 
-# Turn on support for specifying glob ignore path rules in the project format.
-unstable_glob_ignore_paths = []
-
-# Turn on the server half of Rojo's unstable two-way sync feature.
-unstable_two_way_sync = []
-
 # Enable this feature to live-reload assets from the web UI.
 dev_live_assets = []
 
 [workspace]
 members = [
-    "rojo-test",
     "rojo-insta-ext",
     "clibrojo",
     "memofs",
@@ -43,7 +35,6 @@ members = [
 
 default-members = [
     ".",
-    "rojo-test",
     "rojo-insta-ext",
     "memofs",
 ]
@@ -61,12 +52,15 @@ name = "build"
 harness = false
 
 [dependencies]
-memofs = { version = "0.1.0", path = "memofs" }
+memofs = { version = "0.1.2", path = "memofs" }
 
+anyhow = "1.0.27"
 backtrace = "0.3"
+bincode = "1.2.1"
 crossbeam-channel = "0.4.0"
 csv = "1.1.1"
 env_logger = "0.7.1"
+fs-err = "2.2.0"
 futures = "0.1.29"
 globset = "0.4.4"
 humantime = "1.3.0"
@@ -85,17 +79,26 @@ regex = "1.3.1"
 reqwest = "0.9.20"
 ritz = "0.1.0"
 rlua = "0.17.0"
+roblox_install = "0.2.2"
 serde = { version = "1.0", features = ["derive", "rc"] }
 serde_json = "1.0"
-snafu = "0.6.0"
 structopt = "0.3.5"
 termcolor = "1.0.5"
+thiserror = "1.0.11"
 tokio = "0.1.22"
 uuid = { version = "0.8.1", features = ["v4", "serde"] }
 
 [target.'cfg(windows)'.dependencies]
 winreg = "0.6.2"
 
+[build-dependencies]
+memofs = { version = "0.1.3", path = "memofs" }
+
+anyhow = "1.0.27"
+bincode = "1.2.1"
+fs-err = "2.3.0"
+maplit = "1.0.1"
+
 [dev-dependencies]
 rojo-insta-ext = { path = "rojo-insta-ext" }
 

README.md

@@ -13,8 +13,8 @@
     <a href="https://crates.io/crates/rojo">
         <img src="https://img.shields.io/crates/v/rojo.svg?label=latest%20release" alt="Latest server version" />
     </a>
-    <a href="https://rojo.space/docs/0.5.x">
-        <img src="https://img.shields.io/badge/docs-0.5.x-brightgreen.svg" alt="Rojo 0.5.x Documentation" />
+    <a href="https://rojo.space/docs">
+        <img src="https://img.shields.io/badge/docs-website-brightgreen.svg" alt="Rojo Documentation" />
     </a>
 </div>
 
@@ -34,11 +34,10 @@ Rojo enables:
 * Streaming `rbxmx` and `rbxm` models into your game in real time
 * Packaging and deploying your project to Roblox.com from the command line
 
-Soon, Rojo will be able to:
+In the future, Rojo will be able to:
 
-* Automatically convert your existing game to work with Rojo
 * Sync instances from Roblox Studio to the filesystem
-* Automatically manage your assets on Roblox.com, like images and sounds
+* Automatically convert your existing game to work with Rojo
 * Import custom instances like MoonScript code
 
 ## [Documentation](https://rojo.space/docs)
@@ -49,7 +48,7 @@ Check out our [contribution guide](CONTRIBUTING.md) for detailed instructions fo
 
 Pull requests are welcome!
 
-Rojo supports Rust 1.40.0 and newer. The minimum supported version of Rust is based on the latest versions of the dependencies that Rojo has.
+Rojo supports Rust 1.43.1 and newer. The minimum supported version of Rust is based on the latest versions of the dependencies that Rojo has.
 
 ## License
 Rojo is available under the terms of the Mozilla Public License, Version 2.0. See [LICENSE.txt](LICENSE.txt) for details.

assets/default-place-project/default.project.json

@@ -4,27 +4,19 @@
     "$className": "DataModel",
 
     "ReplicatedStorage": {
-      "$className": "ReplicatedStorage",
-
       "Common": {
-        "$path": "src/common"
+        "$path": "src/shared"
       }
     },
 
     "ServerScriptService": {
-      "$className": "ServerScriptService",
-
       "Server": {
         "$path": "src/server"
       }
     },
 
     "StarterPlayer": {
-      "$className": "StarterPlayer",
-
       "StarterPlayerScripts": {
-        "$className": "StarterPlayerScripts",
-
         "Client": {
           "$path": "src/client"
         }
@@ -32,7 +24,6 @@
     },
 
     "Workspace": {
-      "$className": "Workspace",
       "$properties": {
         "FilteringEnabled": true
       },
@@ -60,7 +51,6 @@
       }
     },
     "Lighting": {
-      "$className": "Lighting",
       "$properties": {
         "Ambient": [
           0,
@@ -74,16 +64,9 @@
       }
     },
     "SoundService": {
-      "$className": "SoundService",
       "$properties": {
         "RespectFilteringEnabled": true
       }
-    },
-    "HttpService": {
-      "$className": "HttpService",
-      "$properties": {
-        "HttpEnabled": true
-      }
     }
   }
 }

benches/build.rs

@@ -35,6 +35,7 @@ fn place_setup<P: AsRef<Path>>(input_path: P) -> (TempDir, BuildCommand) {
 
     let options = BuildCommand {
         project: input,
+        watch: false,
         output,
     };
 

build.rs

@@ -0,0 +1,74 @@
+use std::{
+    env, io,
+    path::{Path, PathBuf},
+};
+
+use fs_err as fs;
+use fs_err::File;
+use maplit::hashmap;
+use memofs::VfsSnapshot;
+
+fn snapshot_from_fs_path(path: &Path) -> io::Result<VfsSnapshot> {
+    println!("cargo:rerun-if-changed={}", path.display());
+
+    if path.is_dir() {
+        let mut children = Vec::new();
+
+        for entry in fs::read_dir(path)? {
+            let entry = entry?;
+
+            let file_name = entry.file_name().to_str().unwrap().to_owned();
+
+            // We can skip any TestEZ test files since they aren't necessary for
+            // the plugin to run.
+            if file_name.ends_with(".spec.lua") {
+                continue;
+            }
+
+            let child_snapshot = snapshot_from_fs_path(&entry.path())?;
+            children.push((file_name, child_snapshot));
+        }
+
+        Ok(VfsSnapshot::dir(children))
+    } else {
+        let content = fs::read_to_string(path)?;
+
+        Ok(VfsSnapshot::file(content))
+    }
+}
+
+fn main() -> Result<(), anyhow::Error> {
+    let out_dir = env::var_os("OUT_DIR").unwrap();
+
+    let root_dir = env::var_os("CARGO_MANIFEST_DIR").unwrap();
+    let plugin_root = PathBuf::from(root_dir).join("plugin");
+
+    let plugin_modules = plugin_root.join("modules");
+
+    let snapshot = VfsSnapshot::dir(hashmap! {
+        "default.project.json" => snapshot_from_fs_path(&plugin_root.join("default.project.json"))?,
+        "fmt" => snapshot_from_fs_path(&plugin_root.join("fmt"))?,
+        "http" => snapshot_from_fs_path(&plugin_root.join("http"))?,
+        "log" => snapshot_from_fs_path(&plugin_root.join("log"))?,
+        "rbx_dom_lua" => snapshot_from_fs_path(&plugin_root.join("rbx_dom_lua"))?,
+        "src" => snapshot_from_fs_path(&plugin_root.join("src"))?,
+        "modules" => VfsSnapshot::dir(hashmap! {
+            "roact" => VfsSnapshot::dir(hashmap! {
+                "src" => snapshot_from_fs_path(&plugin_modules.join("roact").join("src"))?
+            }),
+            "promise" => VfsSnapshot::dir(hashmap! {
+                "lib" => snapshot_from_fs_path(&plugin_modules.join("promise").join("lib"))?
+            }),
+            "t" => VfsSnapshot::dir(hashmap! {
+                "lib" => snapshot_from_fs_path(&plugin_modules.join("t").join("lib"))?
+            }),
+        }),
+    });
+
+    let out_path = Path::new(&out_dir).join("plugin.bincode");
+    let out_file = File::create(&out_path)?;
+
+    bincode::serialize_into(out_file, &snapshot)?;
+
+    Ok(())
+}

design.gv

@@ -1,30 +0,0 @@
-digraph Rojo {
-	concentrate = true;
-	node [fontname = "sans-serif"];
-
-	plugin [label="Roblox Studio Plugin"]
-	session [label="Session"]
-	rbx_tree [label="Instance Tree"]
-	imfs [label="In-Memory Filesystem"]
-	fs_impl [label="Filesystem Implementation\n(stubbed in tests)"]
-	fs [label="Real Filesystem"]
-	snapshot_subsystem [label="Snapshot Subsystem\n(reconciler)"]
-	snapshot_generator [label="Snapshot Generator"]
-	user_middleware [label="User Middleware\n(MoonScript, etc.)"]
-	builtin_middleware [label="Built-in Middleware\n(.lua, .rbxm, etc.)"]
-	api [label="Web API"]
-	file_watcher [label="File Watcher"]
-
-	session -> imfs
-	session -> rbx_tree
-	session -> snapshot_subsystem
-	session -> snapshot_generator
-	session -> file_watcher [dir="both"]
-	file_watcher -> imfs
-	snapshot_generator -> user_middleware
-	snapshot_generator -> builtin_middleware
-	plugin -> api [style="dotted"; dir="both"; minlen=2]
-	api -> session
-	imfs -> fs_impl
-	fs_impl -> fs
-}

foreman.toml

@@ -0,0 +1,3 @@
+[tools]
+rojo = { source = "rojo-rbx/rojo", version = "6.0.0-rc.1" }
+run-in-roblox = { source = "rojo-rbx/run-in-roblox", version = "0.3.0" }

memofs/CHANGELOG.md

@@ -1,6 +1,13 @@
 # memofs Changelog
 
 ## Unreleased Changes
+* Added `set_watch_enabled` to `Vfs` and `VfsLock` to allow turning off file watching.
+
+## 0.1.2 (2020-03-29)
+* `VfsSnapshot` now implements Serde's `Serialize` and `Deserialize` traits.
+
+## 0.1.1 (2020-03-18)
+* Improved error messages using the [fs-err](https://crates.io/crates/fs-err) crate.
 
 ## 0.1.0 (2020-03-10)
 * Initial release

memofs/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "memofs"
 description = "Virtual filesystem with configurable backends."
-version = "0.1.0"
+version = "0.1.3"
 authors = ["Lucien Greathouse <me@lpghatguy.com>"]
 edition = "2018"
 readme = "README.md"
@@ -11,5 +11,7 @@ homepage = "https://github.com/rojo-rbx/rojo/tree/master/memofs"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-notify = "4.0.15"
 crossbeam-channel = "0.4.0"
+fs-err = "2.3.0"
+notify = "4.0.15"
+serde = { version = "1.0", features = ["derive"] }

memofs/README.md

@@ -19,4 +19,4 @@ memofs is currently an unstable minimum viable library. Its primary consumer is
 * Configurable caching (write-through, write-around, write-back)
 
 ## License
-memofs is available under the terms of the MIT license. See [LICENSE.txt](LICENSE.txt) or <https://opensource.org/licenses/MIT> for more details.
+memofs is available under the terms of the MIT license. See [LICENSE.txt](LICENSE.txt) or <https://opensource.org/licenses/MIT> for more details.

memofs/src/lib.rs

@@ -140,13 +140,18 @@ pub enum VfsEvent {
 /// the public interfaces to this type.
 struct VfsInner {
     backend: Box<dyn VfsBackend>,
+    watch_enabled: bool,
 }
 
 impl VfsInner {
     fn read<P: AsRef<Path>>(&mut self, path: P) -> io::Result<Arc<Vec<u8>>> {
         let path = path.as_ref();
         let contents = self.backend.read(path)?;
-        self.backend.watch(path)?;
+
+        if self.watch_enabled {
+            self.backend.watch(path)?;
+        }
+
         Ok(Arc::new(contents))
     }
 
@@ -159,7 +164,11 @@ impl VfsInner {
     fn read_dir<P: AsRef<Path>>(&mut self, path: P) -> io::Result<ReadDir> {
         let path = path.as_ref();
         let dir = self.backend.read_dir(path)?;
-        self.backend.watch(path)?;
+
+        if self.watch_enabled {
+            self.backend.watch(path)?;
+        }
+
         Ok(dir)
     }
 
@@ -215,6 +224,7 @@ impl Vfs {
     pub fn new<B: VfsBackend>(backend: B) -> Self {
         let lock = VfsInner {
             backend: Box::new(backend),
+            watch_enabled: true,
         };
 
         Self {
@@ -229,6 +239,16 @@ impl Vfs {
         }
     }
 
+    /// Turns automatic file watching on or off. Enabled by default.
+    ///
+    /// Turning off file watching may be useful for single-use cases, especially
+    /// on platforms like macOS where registering file watches has significant
+    /// performance cost.
+    pub fn set_watch_enabled(&self, enabled: bool) {
+        let mut inner = self.inner.lock().unwrap();
+        inner.watch_enabled = enabled;
+    }
+
     /// Read a file from the VFS, or the underlying backend if it isn't
     /// resident.
     ///
@@ -318,6 +338,15 @@ pub struct VfsLock<'a> {
 }
 
 impl VfsLock<'_> {
+    /// Turns automatic file watching on or off. Enabled by default.
+    ///
+    /// Turning off file watching may be useful for single-use cases, especially
+    /// on platforms like macOS where registering file watches has significant
+    /// performance cost.
+    pub fn set_watch_enabled(&mut self, enabled: bool) {
+        self.inner.watch_enabled = enabled;
+    }
+
     /// Read a file from the VFS, or the underlying backend if it isn't
     /// resident.
     ///

memofs/src/snapshot.rs

@@ -1,8 +1,9 @@
+use serde::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 
 /// A slice of a tree of files. Can be loaded into an
 /// [`InMemoryFs`](struct.InMemoryFs.html).
-#[derive(Debug)]
+#[derive(Debug, Serialize, Deserialize)]
 #[non_exhaustive]
 pub enum VfsSnapshot {
     File {

memofs/src/std_backend.rs

@@ -1,4 +1,3 @@
-use std::fs;
 use std::io;
 use std::path::Path;
 use std::sync::mpsc;
@@ -55,15 +54,15 @@ impl StdBackend {
 
 impl VfsBackend for StdBackend {
     fn read(&mut self, path: &Path) -> io::Result<Vec<u8>> {
-        fs::read(path)
+        fs_err::read(path)
     }
 
     fn write(&mut self, path: &Path, data: &[u8]) -> io::Result<()> {
-        fs::write(path, data)
+        fs_err::write(path, data)
     }
 
     fn read_dir(&mut self, path: &Path) -> io::Result<ReadDir> {
-        let entries: Result<Vec<_>, _> = fs::read_dir(path)?.collect();
+        let entries: Result<Vec<_>, _> = fs_err::read_dir(path)?.collect();
         let mut entries = entries?;
 
         entries.sort_by_cached_key(|entry| entry.file_name());
@@ -78,15 +77,15 @@ impl VfsBackend for StdBackend {
     }
 
     fn remove_file(&mut self, path: &Path) -> io::Result<()> {
-        fs::remove_file(path)
+        fs_err::remove_file(path)
     }
 
     fn remove_dir_all(&mut self, path: &Path) -> io::Result<()> {
-        fs::remove_dir_all(path)
+        fs_err::remove_dir_all(path)
     }
 
     fn metadata(&mut self, path: &Path) -> io::Result<Metadata> {
-        let inner = fs::metadata(path)?;
+        let inner = fs_err::metadata(path)?;
 
         Ok(Metadata {
             is_file: inner.is_file(),

perf-test.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+set -e
+
+cargo build --release
+
+echo "Known good:"
+time rojo build ../uiblox/test-place.project.json -o UIBlox.rbxlx
+
+echo "Current:"
+time ./target/release/rojo build ../uiblox/test-place.project.json -o UIBlox.rbxlx

plugin/default.project.json

@@ -14,6 +14,9 @@
     "Fmt": {
       "$path": "fmt"
     },
+    "RbxDom": {
+      "$path": "rbx_dom_lua"
+    },
     "Roact": {
       "$path": "modules/roact/src"
     },
@@ -22,9 +25,6 @@
     },
     "t": {
       "$path": "modules/t/lib"
-    },
-    "RbxDom": {
-      "$path": "modules/rbx-dom/rbx_dom_lua/src"
     }
   }
 }

plugin/log/init.lua

@@ -53,4 +53,8 @@ function Log.warn(template, ...)
 	end
 end
 
+function Log.error(template, ...)
+	error(Fmt.fmt(template, ...))
+end
+
 return Log

plugin/rbx_dom_lua/.luacheckrc

@@ -0,0 +1,44 @@
+stds.roblox = {
+	read_globals = {
+		game = {
+			other_fields = true,
+		},
+
+		-- Roblox globals
+		"script",
+
+		-- Extra functions
+		"tick", "warn",
+		"wait", "typeof",
+
+		-- Types
+		"CFrame",
+		"Color3",
+		"Enum",
+		"Instance",
+		"NumberRange",
+		"Rect",
+		"UDim", "UDim2",
+		"Vector2", "Vector3",
+		"Vector2int16", "Vector3int16",
+	}
+}
+
+stds.testez = {
+	read_globals = {
+		"describe",
+		"it", "itFOCUS", "itSKIP",
+		"FOCUS", "SKIP", "HACK_NO_XPCALL",
+		"expect",
+	}
+}
+
+ignore = {
+	"212", -- unused arguments
+}
+
+std = "lua51+roblox"
+
+files["**/*.spec.lua"] = {
+	std = "+testez",
+}

plugin/rbx_dom_lua/README.md

@@ -0,0 +1,2 @@
+# rbx_dom_lua
+Roblox Lua implementation of rbx-dom mechanisms, intended to work with rbx_dom_weak and friends.

plugin/rbx_dom_lua/default.project.json

@@ -0,0 +1,6 @@
+{
+  "name": "rbx_dom_lua",
+  "tree": {
+    "$path": "src"
+  }
+}

plugin/rbx_dom_lua/src/EncodedValue.lua

@@ -0,0 +1,242 @@
+local base64 = require(script.Parent.base64)
+
+local function identity(...)
+	return ...
+end
+
+local function unpackDecoder(f)
+	return function(value)
+		return f(unpack(value))
+	end
+end
+
+local function serializeFloat(value)
+	-- TODO: Figure out a better way to serialize infinity and NaN, neither of
+	-- which fit into JSON.
+	if value == math.huge or value == -math.huge then
+		return 999999999 * math.sign(value)
+	end
+
+	return value
+end
+
+local encoders
+encoders = {
+	Bool = identity,
+	Content = identity,
+	Float32 = serializeFloat,
+	Float64 = serializeFloat,
+	Int32 = identity,
+	Int64 = identity,
+	String = identity,
+
+	BinaryString = base64.encode,
+	SharedString = base64.encode,
+
+	BrickColor = function(value)
+		return value.Number
+	end,
+
+	CFrame = function(value)
+		return {value:GetComponents()}
+	end,
+	Color3 = function(value)
+		return {value.r, value.g, value.b}
+	end,
+	NumberRange = function(value)
+		return {value.Min, value.Max}
+	end,
+	NumberSequence = function(value)
+		local keypoints = {}
+
+		for index, keypoint in ipairs(value.Keypoints) do
+			keypoints[index] = {
+				Time = keypoint.Time,
+				Value = keypoint.Value,
+				Envelope = keypoint.Envelope,
+			}
+		end
+
+		return {
+			Keypoints = keypoints,
+		}
+	end,
+	ColorSequence = function(value)
+		local keypoints = {}
+
+		for index, keypoint in ipairs(value.Keypoints) do
+			keypoints[index] = {
+				Time = keypoint.Time,
+				Color = encoders.Color3(keypoint.Value),
+			}
+		end
+
+		return {
+			Keypoints = keypoints,
+		}
+	end,
+	Rect = function(value)
+		return {
+			Min = {value.Min.X, value.Min.Y},
+			Max = {value.Max.X, value.Max.Y},
+		}
+	end,
+	UDim = function(value)
+		return {value.Scale, value.Offset}
+	end,
+	UDim2 = function(value)
+		return {value.X.Scale, value.X.Offset, value.Y.Scale, value.Y.Offset}
+	end,
+	Vector2 = function(value)
+		return {
+			serializeFloat(value.X),
+			serializeFloat(value.Y),
+		}
+	end,
+	Vector2int16 = function(value)
+		return {value.X, value.Y}
+	end,
+	Vector3 = function(value)
+		return {
+			serializeFloat(value.X),
+			serializeFloat(value.Y),
+			serializeFloat(value.Z),
+		}
+	end,
+	Vector3int16 = function(value)
+		return {value.X, value.Y, value.Z}
+	end,
+
+	PhysicalProperties = function(value)
+		if value == nil then
+			return nil
+		else
+			return {
+				Density = value.Density,
+				Friction = value.Friction,
+				Elasticity = value.Elasticity,
+				FrictionWeight = value.FrictionWeight,
+				ElasticityWeight = value.ElasticityWeight,
+			}
+		end
+	end,
+
+	Ref = function(value)
+		return nil
+	end,
+}
+
+local decoders = {
+	Bool = identity,
+	Content = identity,
+	Enum = identity,
+	Float32 = identity,
+	Float64 = identity,
+	Int32 = identity,
+	Int64 = identity,
+	String = identity,
+
+	BinaryString = base64.decode,
+	SharedString = base64.decode,
+
+	BrickColor = BrickColor.new,
+
+	CFrame = unpackDecoder(CFrame.new),
+	Color3 = unpackDecoder(Color3.new),
+	Color3uint8 = unpackDecoder(Color3.fromRGB),
+	NumberRange = unpackDecoder(NumberRange.new),
+	UDim = unpackDecoder(UDim.new),
+	UDim2 = unpackDecoder(UDim2.new),
+	Vector2 = unpackDecoder(Vector2.new),
+	Vector2int16 = unpackDecoder(Vector2int16.new),
+	Vector3 = unpackDecoder(Vector3.new),
+	Vector3int16 = unpackDecoder(Vector3int16.new),
+
+	Rect = function(value)
+		return Rect.new(value.Min[1], value.Min[2], value.Max[1], value.Max[2])
+	end,
+
+	NumberSequence = function(value)
+		local keypoints = {}
+
+		for index, keypoint in ipairs(value.Keypoints) do
+			keypoints[index] = NumberSequenceKeypoint.new(
+				keypoint.Time,
+				keypoint.Value,
+				keypoint.Envelope
+			)
+		end
+
+		return NumberSequence.new(keypoints)
+	end,
+
+	ColorSequence = function(value)
+		local keypoints = {}
+
+		for index, keypoint in ipairs(value.Keypoints) do
+			keypoints[index] = ColorSequenceKeypoint.new(
+				keypoint.Time,
+				Color3.new(unpack(keypoint.Color))
+			)
+		end
+
+		return ColorSequence.new(keypoints)
+	end,
+
+	PhysicalProperties = function(properties)
+		if properties == nil then
+			return nil
+		else
+			return PhysicalProperties.new(
+				properties.Density,
+				properties.Friction,
+				properties.Elasticity,
+				properties.FrictionWeight,
+				properties.ElasticityWeight
+			)
+		end
+	end,
+
+	Ref = function()
+		return nil
+	end,
+}
+
+local EncodedValue = {}
+
+function EncodedValue.decode(encodedValue)
+	local decoder = decoders[encodedValue.Type]
+	if decoder ~= nil then
+		return true, decoder(encodedValue.Value)
+	end
+
+	return false, "Couldn't decode value " .. tostring(encodedValue.Type)
+end
+
+function EncodedValue.encode(rbxValue, propertyType)
+	assert(propertyType ~= nil, "Property type descriptor is required")
+
+	if propertyType.type == "Data" then
+		local encoder = encoders[propertyType.name]
+
+		if encoder == nil then
+			return false, ("Missing encoder for property type %q"):format(propertyType.name)
+		end
+
+		if encoder ~= nil then
+			return true, {
+				Type = propertyType.name,
+				Value = encoder(rbxValue),
+			}
+		end
+	elseif propertyType.type == "Enum" then
+		return true, {
+			Type = "Enum",
+			Value = rbxValue.Value,
+		}
+	end
+
+	return false, ("Unknown property descriptor type %q"):format(tostring(propertyType.type))
+end
+
+return EncodedValue

plugin/rbx_dom_lua/src/EncodedValue.spec.lua

@@ -0,0 +1,127 @@
+return function()
+	local RbxDom = require(script.Parent)
+	local EncodedValue = require(script.Parent.EncodedValue)
+
+	it("should decode Rect values", function()
+		local input = {
+			Type = "Rect",
+			Value = {
+				Min = {1, 2},
+				Max = {3, 4},
+			},
+		}
+
+		local output = Rect.new(1, 2, 3, 4)
+
+		local ok, decoded = EncodedValue.decode(input)
+
+		assert(ok, decoded)
+		expect(decoded).to.equal(output)
+	end)
+
+	it("should decode ColorSequence values", function()
+		local input = {
+			Type = "ColorSequence",
+			Value = {
+				Keypoints = {
+					{
+						Time = 0,
+						Color = { 0.12, 0.34, 0.56 },
+					},
+
+					{
+						Time = 1,
+						Color = { 0.13, 0.33, 0.37 },
+					},
+				}
+			},
+		}
+
+		local output = ColorSequence.new({
+			ColorSequenceKeypoint.new(0, Color3.new(0.12, 0.34, 0.56)),
+			ColorSequenceKeypoint.new(1, Color3.new(0.13, 0.33, 0.37)),
+		})
+
+		local ok, decoded = EncodedValue.decode(input)
+		assert(ok, decoded)
+		expect(decoded).to.equal(output)
+	end)
+
+	it("should decode NumberSequence values", function()
+		local input = {
+			Type = "NumberSequence",
+			Value = {
+				Keypoints = {
+					{
+						Time = 0,
+						Value = 0.5,
+						Envelope = 0,
+					},
+
+					{
+						Time = 1,
+						Value = 0.5,
+						Envelope = 0,
+					},
+				}
+			},
+		}
+
+		local output = NumberSequence.new({
+			NumberSequenceKeypoint.new(0, 0.5, 0),
+			NumberSequenceKeypoint.new(1, 0.5, 0),
+		})
+
+		local ok, decoded = EncodedValue.decode(input)
+		assert(ok, decoded)
+		expect(decoded).to.equal(output)
+	end)
+
+	it("should decode PhysicalProperties values", function()
+		local input = {
+			Type = "PhysicalProperties",
+			Value = {
+				Density = 0.1,
+				Friction = 0.2,
+				Elasticity = 0.3,
+				FrictionWeight = 0.4,
+				ElasticityWeight = 0.5,
+			},
+		}
+
+		local output = PhysicalProperties.new(
+			0.1,
+			0.2,
+			0.3,
+			0.4,
+			0.5
+		)
+
+		local ok, decoded = EncodedValue.decode(input)
+		assert(ok, decoded)
+		expect(decoded).to.equal(output)
+	end)
+
+	-- This part of rbx_dom_lua needs some work still.
+	itSKIP("should encode Rect values", function()
+		local input = Rect.new(10, 20, 30, 40)
+
+		local output = {
+			Type = "Rect",
+			Value = {
+				Min = {10, 20},
+				Max = {30, 40},
+			},
+		}
+
+		local descriptor = RbxDom.findCanonicalPropertyDescriptor("ImageLabel", "SliceCenter")
+		local ok, encoded = EncodedValue.encode(input, descriptor)
+
+		assert(ok, encoded)
+		expect(encoded.Type).to.equal(output.Type)
+		expect(encoded.Value.Min[1]).to.equal(output.Value.Min[1])
+		expect(encoded.Value.Min[2]).to.equal(output.Value.Min[2])
+		expect(encoded.Value.Max[1]).to.equal(output.Value.Max[1])
+		expect(encoded.Value.Max[2]).to.equal(output.Value.Max[2])
+	end)
+end

plugin/rbx_dom_lua/src/Error.lua

@@ -0,0 +1,28 @@
+local Error = {}
+Error.__index = Error
+
+Error.Kind = {
+	UnknownProperty = "UnknownProperty",
+	PropertyNotReadable = "PropertyNotReadable",
+	PropertyNotWritable = "PropertyNotWritable",
+	Roblox = "Roblox",
+}
+
+setmetatable(Error.Kind, {
+	__index = function(_, key)
+		error(("%q is not a valid member of Error.Kind"):format(tostring(key)), 2)
+	end,
+})
+
+function Error.new(kind, extra)
+	return setmetatable({
+		kind = kind,
+		extra = extra,
+	}, Error)
+end
+
+function Error:__tostring()
+	return ("Error(%s: %s)"):format(self.kind, tostring(self.extra))
+end
+
+return Error

plugin/rbx_dom_lua/src/PropertyDescriptor.lua

@@ -0,0 +1,80 @@
+local Error = require(script.Parent.Error)
+local customProperties = require(script.Parent.customProperties)
+
+-- A wrapper around a property descriptor from the reflection database with some
+-- extra convenience methods.
+--
+-- The aim of this API is to facilitate looking up a property once, then reading
+-- from it or writing to it multiple times. It's also useful when a consumer
+-- wants to check additional constraints on the property before trying to use
+-- it, like scriptability.
+local PropertyDescriptor = {}
+PropertyDescriptor.__index = PropertyDescriptor
+
+local function get(container, key)
+	return container[key]
+end
+
+local function set(container, key, value)
+	container[key] = value
+end
+
+function PropertyDescriptor.fromRaw(data, className, propertyName)
+	return setmetatable({
+		scriptability = data.scriptability,
+		className = className,
+		name = propertyName,
+	}, PropertyDescriptor)
+end
+
+function PropertyDescriptor:read(instance)
+	if self.scriptability == "ReadWrite" or self.scriptability == "Read" then
+		local success, value = xpcall(get, debug.traceback, instance, self.name)
+
+		if success then
+			return success, value
+		else
+			return false, Error.new(Error.Kind.Roblox, value)
+		end
+	end
+
+	if self.scriptability == "Custom" then
+		local interface = customProperties[self.className][self.name]
+
+		return interface.read(instance, self.name)
+	end
+
+	if self.scriptability == "None" or self.scriptability == "Write" then
+		local fullName = ("%s.%s"):format(instance.className, self.name)
+
+		return false, Error.new(Error.Kind.PropertyNotReadable, fullName)
+	end
+
+	error(("Internal error: unexpected value of 'scriptability': %s"):format(tostring(self.scriptability)), 2)
+end
+
+function PropertyDescriptor:write(instance, value)
+	if self.scriptability == "ReadWrite" or self.scriptability == "Write" then
+		local success, err = xpcall(set, debug.traceback, instance, self.name, value)
+
+		if success then
+			return success
+		else
+			return false, Error.new(Error.Kind.Roblox, err)
+		end
+	end
+
+	if self.scriptability == "Custom" then
+		local interface = customProperties[self.className][self.name]
+
+		return interface.write(instance, self.name, value)
+	end
+
+	if self.scriptability == "None" or self.scriptability == "Read" then
+		local fullName = ("%s.%s"):format(instance.className, self.name)
+
+		return false, Error.new(Error.Kind.PropertyNotWritable, fullName)
+	end
+end
+
+return PropertyDescriptor

plugin/rbx_dom_lua/src/ReflectionDatabase/init.lua

@@ -0,0 +1,3 @@
+return {
+	classes = require(script.classes)
+}

plugin/rbx_dom_lua/src/base64.lua

@@ -0,0 +1,139 @@
+-- Thanks to Tiffany352 for this base64 implementation!
+
+local floor = math.floor
+local char = string.char
+
+local function encodeBase64(str)
+	local out = {}
+	local nOut = 0
+	local alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+	local strLen = #str
+
+	-- 3 octets become 4 hextets
+	for i = 1, strLen - 2, 3 do
+		local b1, b2, b3 = str:byte(i, i + 3)
+		local word = b3 + b2 * 256 + b1 * 256 * 256
+
+		local h4 = word % 64 + 1
+		word = floor(word / 64)
+		local h3 = word % 64 + 1
+		word = floor(word / 64)
+		local h2 = word % 64 + 1
+		word = floor(word / 64)
+		local h1 = word % 64 + 1
+
+		out[nOut + 1] = alphabet:sub(h1, h1)
+		out[nOut + 2] = alphabet:sub(h2, h2)
+		out[nOut + 3] = alphabet:sub(h3, h3)
+		out[nOut + 4] = alphabet:sub(h4, h4)
+		nOut = nOut + 4
+	end
+
+	local remainder = strLen % 3
+
+	if remainder == 2 then
+		-- 16 input bits -> 3 hextets (2 full, 1 partial)
+		local b1, b2 = str:byte(-2, -1)
+		-- partial is 4 bits long, leaving 2 bits of zero padding ->
+		-- offset = 4
+		local word = b2 * 4 + b1 * 4 * 256
+
+		local h3 = word % 64 + 1
+		word = floor(word / 64)
+		local h2 = word % 64 + 1
+		word = floor(word / 64)
+		local h1 = word % 64 + 1
+
+		out[nOut + 1] = alphabet:sub(h1, h1)
+		out[nOut + 2] = alphabet:sub(h2, h2)
+		out[nOut + 3] = alphabet:sub(h3, h3)
+		out[nOut + 4] = "="
+	elseif remainder == 1 then
+		-- 8 input bits -> 2 hextets (2 full, 1 partial)
+		local b1 = str:byte(-1, -1)
+		-- partial is 2 bits long, leaving 4 bits of zero padding ->
+		-- offset = 16
+		local word = b1 * 16
+
+		local h2 = word % 64 + 1
+		word = floor(word / 64)
+		local h1 = word % 64 + 1
+
+		out[nOut + 1] = alphabet:sub(h1, h1)
+		out[nOut + 2] = alphabet:sub(h2, h2)
+		out[nOut + 3] = "="
+		out[nOut + 4] = "="
+	end
+	-- if the remainder is 0, then no work is needed
+
+	return table.concat(out, "")
+end
+
+local function decodeBase64(str)
+	local out = {}
+	local nOut = 0
+	local alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
+	local strLen = #str
+	local acc = 0
+	local nAcc = 0
+
+	local alphabetLut = {}
+	for i = 1, #alphabet do
+		alphabetLut[alphabet:sub(i, i)] = i - 1
+	end
+
+	-- 4 hextets become 3 octets
+	for i = 1, strLen do
+		local ch = str:sub(i, i)
+		local byte = alphabetLut[ch]
+		if byte then
+			acc = acc * 64 + byte
+			nAcc = nAcc + 1
+		end
+
+		if nAcc == 4 then
+			local b3 = acc % 256
+			acc = floor(acc / 256)
+			local b2 = acc % 256
+			acc = floor(acc / 256)
+			local b1 = acc % 256
+
+			out[nOut + 1] = char(b1)
+			out[nOut + 2] = char(b2)
+			out[nOut + 3] = char(b3)
+			nOut = nOut + 3
+			nAcc = 0
+			acc = 0
+		end
+	end
+
+	if nAcc == 3 then
+		-- 3 hextets -> 16 bit output
+		acc = acc * 64
+		acc = floor(acc / 256)
+		local b2 = acc % 256
+		acc = floor(acc / 256)
+		local b1 = acc % 256
+
+		out[nOut + 1] = char(b1)
+		out[nOut + 2] = char(b2)
+	elseif nAcc == 2 then
+		-- 2 hextets -> 8 bit output
+		acc = acc * 64
+		acc = floor(acc / 256)
+		acc = acc * 64
+		acc = floor(acc / 256)
+		local b1 = acc % 256
+
+		out[nOut + 1] = char(b1)
+	elseif nAcc == 1 then
+		error("Base64 has invalid length")
+	end
+
+	return table.concat(out, "")
+end
+
+return {
+	decode = decodeBase64,
+	encode = encodeBase64,
+}

plugin/rbx_dom_lua/src/base64.spec.lua

@@ -0,0 +1,29 @@
+return function()
+	local base64 = require(script.Parent.base64)
+
+	it("should encode and decode", function()
+		local function try(str, expected)
+			local encoded = base64.encode(str)
+			expect(encoded).to.equal(expected)
+			expect(base64.decode(encoded)).to.equal(str)
+		end
+
+		try("Man", "TWFu")
+		try("Ma", "TWE=")
+		try("M", "TQ==")
+		try("ManM", "TWFuTQ==")
+		try(
+			[[Man is distinguished, not only by his reason, but by this ]]..
+			[[singular passion from other animals, which is a lust of the ]]..
+			[[mind, that by a perseverance of delight in the continued and ]]..
+			[[indefatigable generation of knowledge, exceeds the short ]]..
+			[[vehemence of any carnal pleasure.]],
+			[[TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sI]]..
+			[[GJ1dCBieSB0aGlzIHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYW]]..
+			[[xzLCB3aGljaCBpcyBhIGx1c3Qgb2YgdGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJ]]..
+			[[zZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGludWVkIGFuZCBpbmRl]]..
+			[[ZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRoZ]]..
+			[[SBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4=]]
+		)
+	end)
+end

plugin/rbx_dom_lua/src/customProperties.lua

@@ -0,0 +1,47 @@
+local CollectionService = game:GetService("CollectionService")
+
+-- Defines how to read and write properties that aren't directly scriptable.
+--
+-- The reflection database refers to these as having scriptability = "Custom"
+return {
+	Instance = {
+		Tags = {
+			read = function(instance, key)
+				local tagList = CollectionService:GetTags(instance)
+
+				return true, table.concat(tagList, "\0")
+			end,
+			write = function(instance, key, value)
+				local existingTags = CollectionService:GetTags(instance)
+
+				local unseenTags = {}
+				for _, tag in ipairs(existingTags) do
+					unseenTags[tag] = true
+				end
+
+				local tagList = string.split(value, "\0")
+				for _, tag in ipairs(tagList) do
+					unseenTags[tag] = nil
+					CollectionService:AddTag(instance, tag)
+				end
+
+				for tag in pairs(unseenTags) do
+					CollectionService:RemoveTag(instance, tag)
+				end
+
+				return true
+			end,
+		},
+	},
+	LocalizationTable = {
+		Contents = {
+			read = function(instance, key)
+				return true, instance:GetContents()
+			end,
+			write = function(instance, key, value)
+				instance:SetContents(value)
+				return true
+			end,
+		},
+	},
+}

plugin/rbx_dom_lua/src/init.lua

@@ -0,0 +1,67 @@
+local ReflectionDatabase = require(script.ReflectionDatabase)
+local Error = require(script.Error)
+local PropertyDescriptor = require(script.PropertyDescriptor)
+
+local function findCanonicalPropertyDescriptor(className, propertyName)
+	local currentClassName = className
+
+	repeat
+		local currentClass = ReflectionDatabase.classes[currentClassName]
+
+		if currentClass == nil then
+			return currentClass
+		end
+
+		local propertyData = currentClass.properties[propertyName]
+		if propertyData ~= nil then
+			if propertyData.isCanonical then
+				return PropertyDescriptor.fromRaw(propertyData, currentClassName, propertyName)
+			end
+
+			if propertyData.canonicalName ~= nil then
+				return PropertyDescriptor.fromRaw(
+					currentClass.properties[propertyData.canonicalName],
+					currentClassName,
+					propertyData.canonicalName)
+			end
+
+			return nil
+		end
+
+		currentClassName = currentClass.superclass
+	until currentClassName == nil
+
+	return nil
+end
+
+local function readProperty(instance, propertyName)
+	local descriptor = findCanonicalPropertyDescriptor(instance.ClassName, propertyName)
+
+	if descriptor == nil then
+		local fullName = ("%s.%s"):format(instance.className, propertyName)
+
+		return false, Error.new(Error.Kind.UnknownProperty, fullName)
+	end
+
+	return descriptor:read(instance)
+end
+
+local function writeProperty(instance, propertyName, value)
+	local descriptor = findCanonicalPropertyDescriptor(instance.ClassName, propertyName)
+
+	if descriptor == nil then
+		local fullName = ("%s.%s"):format(instance.className, propertyName)
+
+		return false, Error.new(Error.Kind.UnknownProperty, fullName)
+	end
+
+	return descriptor:write(instance, value)
+end
+
+return {
+	readProperty = readProperty,
+	writeProperty = writeProperty,
+	findCanonicalPropertyDescriptor = findCanonicalPropertyDescriptor,
+	Error = Error,
+	EncodedValue = require(script.EncodedValue),
+}

plugin/rbx_dom_lua/src/init.spec.lua

@@ -0,0 +1,7 @@
+return function()
+	local RbxDom = require(script.Parent)
+
+	it("should load", function()
+		expect(RbxDom).to.be.ok()
+	end)
+end

plugin/rbx_dom_lua/test-place.project.json

@@ -0,0 +1,35 @@
+{
+  "name": "rbx_dom_lua test place",
+  "tree": {
+    "$className": "DataModel",
+    "ReplicatedStorage": {
+      "$className": "ReplicatedStorage",
+
+      "RbxDom": {
+        "$path": "src"
+      },
+      "TestEZ": {
+        "$path": "modules/testez/lib"
+      }
+    },
+    "ServerScriptService": {
+      "$className": "ServerScriptService",
+
+      "Run Tests": {
+        "$path": "test.server.lua"
+      }
+    },
+    "Players": {
+      "$className": "Players",
+      "$properties": {
+        "CharacterAutoLoads": false
+      }
+    },
+    "HttpService": {
+      "$className": "HttpService",
+      "$properties": {
+        "HttpEnabled": true
+      }
+    }
+  }
+}

plugin/rbx_dom_lua/test.server.lua

@@ -0,0 +1,7 @@
+local ReplicatedStorage = game:GetService("ReplicatedStorage")
+
+local LIB_ROOT = ReplicatedStorage.RbxDom
+
+local TestEZ = require(ReplicatedStorage.TestEZ)
+
+TestEZ.TestBootstrap:run({LIB_ROOT})

plugin/src/ApiContext.lua

@@ -233,4 +233,19 @@ function ApiContext:retrieveMessages()
 		end)
 end
 
+function ApiContext:open(id)
+	local url = ("%s/api/open/%s"):format(self.__baseUrl, id)
+
+	return Http.post(url, "")
+		:andThen(rejectFailedRequests)
+		:andThen(Http.Response.json)
+		:andThen(function(body)
+			if body.sessionId ~= self.__sessionId then
+				return Promise.reject("Server changed ID")
+			end
+
+			return nil
+		end)
+end
+
 return ApiContext

plugin/src/Components/App.lua

@@ -13,11 +13,11 @@ local Version = require(Plugin.Version)
 local preloadAssets = require(Plugin.preloadAssets)
 local strict = require(Plugin.strict)
 
-local Theme = require(Plugin.Components.Theme)
 local ConnectPanel = require(Plugin.Components.ConnectPanel)
 local ConnectingPanel = require(Plugin.Components.ConnectingPanel)
 local ConnectionActivePanel = require(Plugin.Components.ConnectionActivePanel)
 local ErrorPanel = require(Plugin.Components.ErrorPanel)
+local SettingsPanel = require(Plugin.Components.SettingsPanel)
 
 local e = Roact.createElement
 
@@ -62,6 +62,7 @@ local AppStatus = strict("AppStatus", {
 	Connecting = "Connecting",
 	Connected = "Connected",
 	Error = "Error",
+	Settings = "Settings",
 })
 
 local App = Roact.Component:extend("App")
@@ -74,10 +75,7 @@ function App:init()
 
 	self.signals = {}
 	self.serveSession = nil
-
-	self.displayedVersion = DevSettings:isEnabled()
-		and Config.codename
-		or Version.display(Config.version)
+	self.displayedVersion = Version.display(Config.version)
 
 	local toolbar = self.props.plugin:CreateToolbar("Rojo " .. self.displayedVersion)
 
@@ -109,12 +107,14 @@ function App:init()
 	end)
 end
 
-function App:startSession(address, port)
+function App:startSession(address, port, sessionOptions)
 	Log.trace("Starting new session")
 
 	local baseUrl = ("http://%s:%s"):format(address, port)
 	self.serveSession = ServeSession.new({
 		apiContext = ApiContext.new(baseUrl),
+		openScriptsExternally = sessionOptions.openScriptsExternally,
+		twoWaySync = sessionOptions.twoWaySync,
 	})
 
 	self.serveSession:onStatusChanged(function(status, details)
@@ -155,8 +155,13 @@ function App:render()
 	if self.state.appStatus == AppStatus.NotStarted then
 		children = {
 			ConnectPanel = e(ConnectPanel, {
-				startSession = function(address, port)
-					self:startSession(address, port)
+				startSession = function(address, port, settings)
+					self:startSession(address, port, settings)
+				end,
+				openSettings = function()
+					self:setState({
+						appStatus = AppStatus.Settings,
+					})
 				end,
 				cancel = function()
 					Log.trace("Canceling session configuration")
@@ -169,7 +174,7 @@ function App:render()
 		}
 	elseif self.state.appStatus == AppStatus.Connecting then
 		children = {
-			ConnectingPanel = Roact.createElement(ConnectingPanel),
+			ConnectingPanel = e(ConnectingPanel),
 		}
 	elseif self.state.appStatus == AppStatus.Connected then
 		children = {
@@ -187,9 +192,19 @@ function App:render()
 				end,
 			}),
 		}
+	elseif self.state.appStatus == AppStatus.Settings then
+		children = {
+			e(SettingsPanel, {
+				back = function()
+					self:setState({
+						appStatus = AppStatus.NotStarted,
+					})
+				end,
+			}),
+		}
 	elseif self.state.appStatus == AppStatus.Error then
 		children = {
-			ErrorPanel = Roact.createElement(ErrorPanel, {
+			ErrorPanel = e(ErrorPanel, {
 				errorMessage = self.state.errorMessage,
 				onDismiss = function()
 					self:setState({
@@ -200,11 +215,9 @@ function App:render()
 		}
 	end
 
-	return Roact.createElement(Theme.StudioProvider, nil, {
-		UI = Roact.createElement(Roact.Portal, {
-			target = self.dockWidget,
-		}, children),
-	})
+	return e(Roact.Portal, {
+		target = self.dockWidget,
+	}, children)
 end
 
 function App:didMount()

plugin/src/Components/Checkbox.lua

@@ -0,0 +1,39 @@
+local Rojo = script:FindFirstAncestor("Rojo")
+local Plugin = Rojo.Plugin
+
+local Roact = require(Rojo.Roact)
+
+local Theme = require(Plugin.Components.Theme)
+
+local e = Roact.createElement
+
+local function Checkbox(props)
+	local checked = props.checked
+	local layoutOrder = props.layoutOrder
+	local onChange = props.onChange
+
+	return Theme.with(function(theme)
+		return e("ImageButton", {
+			LayoutOrder = layoutOrder,
+			Size = UDim2.new(0, 20, 0, 20),
+			BorderSizePixel = 2,
+			BorderColor3 = theme.Text2,
+			BackgroundColor3 = theme.Background2,
+
+			[Roact.Event.Activated] = function()
+				onChange(not checked)
+			end,
+		}, {
+			Indicator = e("Frame", {
+				Size = UDim2.new(0, 18, 0, 18),
+				Position = UDim2.new(0.5, 0, 0.5, 0),
+				AnchorPoint = Vector2.new(0.5, 0.5),
+				BorderSizePixel = 0,
+				BackgroundColor3 = theme.Brand1,
+				BackgroundTransparency = checked and 0 or 1,
+			})
+		})
+	end)
+end
+
+return Checkbox

plugin/src/Components/ConnectPanel.lua

@@ -11,6 +11,7 @@ local FitList = require(Plugin.Components.FitList)
 local FitText = require(Plugin.Components.FitText)
 local FormButton = require(Plugin.Components.FormButton)
 local FormTextInput = require(Plugin.Components.FormTextInput)
+local PluginSettings = require(Plugin.Components.PluginSettings)
 
 local e = Roact.createElement
 
@@ -25,138 +26,157 @@ end
 
 function ConnectPanel:render()
 	local startSession = self.props.startSession
+	local openSettings = self.props.openSettings
 
 	return Theme.with(function(theme)
-		return e(Panel, nil, {
-			Layout = e("UIListLayout", {
-				SortOrder = Enum.SortOrder.LayoutOrder,
-				HorizontalAlignment = Enum.HorizontalAlignment.Center,
-				VerticalAlignment = Enum.VerticalAlignment.Center,
-			}),
+		return PluginSettings.with(function(settings)
+			return e(Panel, nil, {
+				Layout = e("UIListLayout", {
+					SortOrder = Enum.SortOrder.LayoutOrder,
+					HorizontalAlignment = Enum.HorizontalAlignment.Center,
+					VerticalAlignment = Enum.VerticalAlignment.Center,
+				}),
 
-			Inputs = e(FitList, {
-				containerProps = {
-					BackgroundTransparency = 1,
-					LayoutOrder = 1,
-				},
-				layoutProps = {
-					FillDirection = Enum.FillDirection.Horizontal,
-					Padding = UDim.new(0, 8),
-				},
-				paddingProps = {
-					PaddingTop = UDim.new(0, 20),
-					PaddingBottom = UDim.new(0, 10),
-					PaddingLeft = UDim.new(0, 24),
-					PaddingRight = UDim.new(0, 24),
-				},
-			}, {
-				Address = e(FitList, {
+				Inputs = e(FitList, {
 					containerProps = {
-						LayoutOrder = 1,
 						BackgroundTransparency = 1,
+						LayoutOrder = 1,
 					},
 					layoutProps = {
-						Padding = UDim.new(0, 4),
+						FillDirection = Enum.FillDirection.Horizontal,
+						Padding = UDim.new(0, 8),
+					},
+					paddingProps = {
+						PaddingTop = UDim.new(0, 20),
+						PaddingBottom = UDim.new(0, 10),
+						PaddingLeft = UDim.new(0, 24),
+						PaddingRight = UDim.new(0, 24),
 					},
 				}, {
-					Label = e(FitText, {
-						Kind = "TextLabel",
-						LayoutOrder = 1,
-						BackgroundTransparency = 1,
-						TextXAlignment = Enum.TextXAlignment.Left,
-						Font = theme.TitleFont,
-						TextSize = 20,
-						Text = "Address",
-						TextColor3 = theme.Text1,
+					Address = e(FitList, {
+						containerProps = {
+							LayoutOrder = 1,
+							BackgroundTransparency = 1,
+						},
+						layoutProps = {
+							Padding = UDim.new(0, 4),
+						},
+					}, {
+						Label = e(FitText, {
+							Kind = "TextLabel",
+							LayoutOrder = 1,
+							BackgroundTransparency = 1,
+							TextXAlignment = Enum.TextXAlignment.Left,
+							Font = theme.TitleFont,
+							TextSize = 20,
+							Text = "Address",
+							TextColor3 = theme.Text1,
+						}),
+
+						Input = e(FormTextInput, {
+							layoutOrder = 2,
+							width = UDim.new(0, 220),
+							value = self.state.address,
+							placeholderValue = Config.defaultHost,
+							onValueChange = function(newValue)
+								self:setState({
+									address = newValue,
+								})
+							end,
+						}),
 					}),
 
-					Input = e(FormTextInput, {
-						layoutOrder = 2,
-						width = UDim.new(0, 220),
-						value = self.state.address,
-						placeholderValue = Config.defaultHost,
-						onValueChange = function(newValue)
-							self:setState({
-								address = newValue,
-							})
-						end,
+					Port = e(FitList, {
+						containerProps = {
+							LayoutOrder = 2,
+							BackgroundTransparency = 1,
+						},
+						layoutProps = {
+							Padding = UDim.new(0, 4),
+						},
+					}, {
+						Label = e(FitText, {
+							Kind = "TextLabel",
+							LayoutOrder = 1,
+							BackgroundTransparency = 1,
+							TextXAlignment = Enum.TextXAlignment.Left,
+							Font = theme.TitleFont,
+							TextSize = 20,
+							Text = "Port",
+							TextColor3 = theme.Text1,
+						}),
+
+						Input = e(FormTextInput, {
+							layoutOrder = 2,
+							width = UDim.new(0, 80),
+							value = self.state.port,
+							placeholderValue = Config.defaultPort,
+							onValueChange = function(newValue)
+								self:setState({
+									port = newValue,
+								})
+							end,
+						}),
 					}),
 				}),
 
-				Port = e(FitList, {
+				Buttons = e(FitList, {
+					fitAxes = "Y",
 					containerProps = {
+						BackgroundTransparency = 1,
 						LayoutOrder = 2,
-						BackgroundTransparency = 1,
+						Size = UDim2.new(1, 0, 0, 0),
 					},
 					layoutProps = {
-						Padding = UDim.new(0, 4),
+						FillDirection = Enum.FillDirection.Horizontal,
+						HorizontalAlignment = Enum.HorizontalAlignment.Right,
+						Padding = UDim.new(0, 8),
+					},
+					paddingProps = {
+						PaddingTop = UDim.new(0, 0),
+						PaddingBottom = UDim.new(0, 20),
+						PaddingLeft = UDim.new(0, 24),
+						PaddingRight = UDim.new(0, 24),
 					},
 				}, {
-					Label = e(FitText, {
-						Kind = "TextLabel",
-						LayoutOrder = 1,
-						BackgroundTransparency = 1,
-						TextXAlignment = Enum.TextXAlignment.Left,
-						Font = theme.TitleFont,
-						TextSize = 20,
-						Text = "Port",
-						TextColor3 = theme.Text1,
+					e(FormButton, {
+						layoutOrder = 1,
+						text = "Settings",
+						secondary = true,
+						onClick = function()
+							if openSettings ~= nil then
+								openSettings()
+							end
+						end,
 					}),
 
-					Input = e(FormTextInput, {
+					e(FormButton, {
 						layoutOrder = 2,
-						width = UDim.new(0, 80),
-						value = self.state.port,
-						placeholderValue = Config.defaultPort,
-						onValueChange = function(newValue)
-							self:setState({
-								port = newValue,
-							})
+						text = "Connect",
+						onClick = function()
+							if startSession ~= nil then
+								local address = self.state.address
+								if address:len() == 0 then
+									address = Config.defaultHost
+								end
+
+								local port = self.state.port
+								if port:len() == 0 then
+									port = Config.defaultPort
+								end
+
+								local sessionOptions = {
+									openScriptsExternally = settings:get("openScriptsExternally"),
+									twoWaySync = settings:get("twoWaySync"),
+								}
+
+								startSession(address, port, sessionOptions)
+							end
 						end,
 					}),
 				}),
-			}),
-
-			Buttons = e(FitList, {
-				fitAxes = "Y",
-				containerProps = {
-					BackgroundTransparency = 1,
-					LayoutOrder = 2,
-					Size = UDim2.new(1, 0, 0, 0),
-				},
-				layoutProps = {
-					FillDirection = Enum.FillDirection.Horizontal,
-					HorizontalAlignment = Enum.HorizontalAlignment.Right,
-					Padding = UDim.new(0, 8),
-				},
-				paddingProps = {
-					PaddingTop = UDim.new(0, 0),
-					PaddingBottom = UDim.new(0, 20),
-					PaddingLeft = UDim.new(0, 24),
-					PaddingRight = UDim.new(0, 24),
-				},
-			}, {
-				e(FormButton, {
-					layoutOrder = 2,
-					text = "Connect",
-					onClick = function()
-						if startSession ~= nil then
-							local address = self.state.address
-							if address:len() == 0 then
-								address = Config.defaultHost
-							end
-
-							local port = self.state.port
-							if port:len() == 0 then
-								port = Config.defaultPort
-							end
-
-							startSession(address, port)
-						end
-					end,
-				}),
-			}),
-		})
+			})
+		end)
 	end)
 end
 

plugin/src/Components/PluginSettings.lua

@@ -0,0 +1,121 @@
+--[[
+	Persistent plugin settings that can be accessed via Roact context.
+]]
+
+local Rojo = script:FindFirstAncestor("Rojo")
+
+local Roact = require(Rojo.Roact)
+
+local defaultSettings = {
+	openScriptsExternally = false,
+	twoWaySync = false,
+}
+
+local Settings = {}
+Settings.__index = Settings
+
+function Settings.fromPlugin(plugin)
+	local values = {}
+
+	for name, defaultValue in pairs(defaultSettings) do
+		local savedValue = plugin:GetSetting("Rojo_" .. name)
+
+		if savedValue == nil then
+			plugin:SetSetting("Rojo_" .. name, defaultValue)
+			values[name] = defaultValue
+		else
+			values[name] = savedValue
+		end
+	end
+
+	return setmetatable({
+		__values = values,
+		__plugin = plugin,
+		__updateListeners = {},
+	}, Settings)
+end
+
+function Settings:get(name)
+	if defaultSettings[name] == nil then
+		error("Invalid setings name " .. tostring(name), 2)
+	end
+
+	return self.__values[name]
+end
+
+function Settings:set(name, value)
+	self.__plugin:SetSetting("Rojo_" .. name, value)
+	self.__values[name] = value
+
+	for callback in pairs(self.__updateListeners) do
+		callback(name, value)
+	end
+end
+
+function Settings:onUpdate(newCallback)
+	local newListeners = {}
+	for callback in pairs(self.__updateListeners) do
+		newListeners[callback] = true
+	end
+
+	newListeners[newCallback] = true
+	self.__updateListeners = newListeners
+
+	return function()
+		local newListeners = {}
+		for callback in pairs(self.__updateListeners) do
+			if callback ~= newCallback then
+				newListeners[callback] = true
+			end
+		end
+
+		self.__updateListeners = newListeners
+	end
+end
+
+local Context = Roact.createContext(nil)
+
+local StudioProvider = Roact.Component:extend("StudioProvider")
+
+function StudioProvider:init()
+	self.settings = Settings.fromPlugin(self.props.plugin)
+end
+
+function StudioProvider:render()
+	return Roact.createElement(Context.Provider, {
+		value = self.settings,
+	}, self.props[Roact.Children])
+end
+
+local InternalConsumer = Roact.Component:extend("InternalConsumer")
+
+function InternalConsumer:render()
+	return self.props.render(self.props.settings)
+end
+
+function InternalConsumer:didMount()
+	self.disconnect = self.props.settings:onUpdate(function()
+		-- Trigger a dummy state update to update the settings consumer.
+		self:setState({})
+	end)
+end
+
+function InternalConsumer:willUnmount()
+	self.disconnect()
+end
+
+local function with(callback)
+	return Roact.createElement(Context.Consumer, {
+		render = function(settings)
+			return Roact.createElement(InternalConsumer, {
+				settings = settings,
+				render = callback,
+			})
+		end,
+	})
+end
+
+return {
+	StudioProvider = StudioProvider,
+	with = with,
+}

plugin/src/Components/SettingsPanel.lua

@@ -0,0 +1,119 @@
+local Roact = require(script:FindFirstAncestor("Rojo").Roact)
+
+local Plugin = script:FindFirstAncestor("Plugin")
+
+local Checkbox = require(Plugin.Components.Checkbox)
+local FitList = require(Plugin.Components.FitList)
+local FitText = require(Plugin.Components.FitText)
+local FormButton = require(Plugin.Components.FormButton)
+local Panel = require(Plugin.Components.Panel)
+local PluginSettings = require(Plugin.Components.PluginSettings)
+local Theme = require(Plugin.Components.Theme)
+
+local e = Roact.createElement
+
+local SettingsPanel = Roact.Component:extend("SettingsPanel")
+
+function SettingsPanel:render()
+	local back = self.props.back
+
+	return Theme.with(function(theme)
+		return PluginSettings.with(function(settings)
+			return e(Panel, nil, {
+				Layout = Roact.createElement("UIListLayout", {
+					HorizontalAlignment = Enum.HorizontalAlignment.Center,
+					VerticalAlignment = Enum.VerticalAlignment.Center,
+					SortOrder = Enum.SortOrder.LayoutOrder,
+					Padding = UDim.new(0, 16),
+				}),
+
+				OpenScriptsExternally = e(FitList, {
+					containerProps = {
+						LayoutOrder = 1,
+						BackgroundTransparency = 1,
+					},
+					layoutProps = {
+						Padding = UDim.new(0, 4),
+						FillDirection = Enum.FillDirection.Horizontal,
+						HorizontalAlignment = Enum.HorizontalAlignment.Left,
+						VerticalAlignment = Enum.VerticalAlignment.Center,
+					},
+				}, {
+					Label = e(FitText, {
+						Kind = "TextLabel",
+						LayoutOrder = 1,
+						BackgroundTransparency = 1,
+						TextXAlignment = Enum.TextXAlignment.Left,
+						Font = theme.MainFont,
+						TextSize = 16,
+						Text = "Open Scripts Externally",
+						TextColor3 = theme.Text1,
+					}),
+
+					Padding = e("Frame", {
+						Size = UDim2.new(0, 8, 0, 0),
+						BackgroundTransparency = 1,
+						LayoutOrder = 2,
+					}),
+
+					Input = e(Checkbox, {
+						layoutOrder = 3,
+						checked = settings:get("openScriptsExternally"),
+						onChange = function(newValue)
+							settings:set("openScriptsExternally", not settings:get("openScriptsExternally"))
+						end,
+					}),
+				}),
+
+				TwoWaySync = e(FitList, {
+					containerProps = {
+						LayoutOrder = 2,
+						BackgroundTransparency = 1,
+					},
+					layoutProps = {
+						Padding = UDim.new(0, 4),
+						FillDirection = Enum.FillDirection.Horizontal,
+						HorizontalAlignment = Enum.HorizontalAlignment.Left,
+						VerticalAlignment = Enum.VerticalAlignment.Center,
+					},
+				}, {
+					Label = e(FitText, {
+						Kind = "TextLabel",
+						LayoutOrder = 1,
+						BackgroundTransparency = 1,
+						TextXAlignment = Enum.TextXAlignment.Left,
+						Font = theme.MainFont,
+						TextSize = 16,
+						Text = "Two-Way Sync (Experimental!)",
+						TextColor3 = theme.Text1,
+					}),
+
+					Padding = e("Frame", {
+						Size = UDim2.new(0, 8, 0, 0),
+						BackgroundTransparency = 1,
+						LayoutOrder = 2,
+					}),
+
+					Input = e(Checkbox, {
+						layoutOrder = 3,
+						checked = settings:get("twoWaySync"),
+						onChange = function(newValue)
+							settings:set("twoWaySync", not settings:get("twoWaySync"))
+						end,
+					}),
+				}),
+
+				BackButton = e(FormButton, {
+					layoutOrder = 4,
+					text = "Okay",
+					secondary = true,
+					onClick = function()
+						back()
+					end,
+				}),
+			})
+		end)
+	end)
+end
+
+return SettingsPanel

plugin/src/Components/Theme.lua

@@ -5,7 +5,16 @@
 	name. This isn't exactly best practice.
 ]]
 
-local Studio = settings():GetService("Studio")
+-- Studio does not exist outside Roblox Studio, so we'll lazily initialize it
+-- when possible.
+local _Studio
+local function getStudio()
+	if _Studio == nil then
+		_Studio = settings():GetService("Studio")
+	end
+
+	return _Studio
+end
 
 local Rojo = script:FindFirstAncestor("Rojo")
 
@@ -52,7 +61,7 @@ local StudioProvider = Roact.Component:extend("StudioProvider")
 
 -- Pull the current theme from Roblox Studio and update state with it.
 function StudioProvider:updateTheme()
-	local studioTheme = Studio.Theme
+	local studioTheme = getStudio().Theme
 
 	if studioTheme.Name == "Light" then
 		self:setState({
@@ -82,7 +91,7 @@ function StudioProvider:render()
 end
 
 function StudioProvider:didMount()
-	self.connection = Studio.ThemeChanged:Connect(function()
+	self.connection = getStudio().ThemeChanged:Connect(function()
 		self:updateTheme()
 	end)
 end

plugin/src/Config.lua

@@ -5,8 +5,8 @@ local isDevBuild = script.Parent.Parent:FindFirstChild("ROJO_DEV_BUILD") ~= nil
 return strict("Config", {
 	isDevBuild = isDevBuild,
 	codename = "Epiphany",
-	version = {0, 6, 0, "-alpha.3"},
-	expectedServerVersionString = "0.6.0 or newer",
+	version = {6, 0, 0, "-rc.2"},
+	expectedServerVersionString = "6.0 or newer",
 	protocolVersion = 3,
 	defaultHost = "localhost",
 	defaultPort = 34872,

plugin/src/DevSettings.lua

@@ -25,14 +25,6 @@ local VALUES = {
 			[Environment.Test] = true,
 		},
 	},
-	UnstableTwoWaySync = {
-		type = "BoolValue",
-		values = {
-			[Environment.User] = false,
-			[Environment.Dev] = false,
-			[Environment.Test] = false,
-		},
-	},
 }
 
 local CONTAINER_NAME = "RojoDevSettings" .. Config.codename
@@ -140,10 +132,6 @@ function DevSettings:shouldTypecheck()
 	return getValue("TypecheckingEnabled")
 end
 
-function DevSettings:twoWaySyncEnabled()
-	return getValue("UnstableTwoWaySync")
-end
-
 function _G.ROJO_DEV_CREATE()
 	DevSettings:createDevSettings()
 end

plugin/src/InstanceMap.lua

@@ -11,15 +11,38 @@ InstanceMap.__index = InstanceMap
 
 function InstanceMap.new(onInstanceChanged)
 	local self = {
+		-- A map from IDs to instances.
 		fromIds = {},
+
+		-- A map from instances to IDs.
 		fromInstances = {},
+
+		-- A set of all instances that updates should be paused for. This set
+		-- should generally be empty, and will be filled by pauseInstance
+		-- temporarily.
+		pausedUpdateInstances = {},
+
+		-- A map from instances to a signal or list of signals connected to it.
 		instancesToSignal = {},
+
+		-- Callback that's invoked whenever an instance is changed and it was
+		-- not paused.
 		onInstanceChanged = onInstanceChanged,
 	}
 
 	return setmetatable(self, InstanceMap)
 end
 
+function InstanceMap:size()
+	local size = 0
+
+	for _ in pairs(self.fromIds) do
+		size = size + 1
+	end
+
+	return size
+end
+
 --[[
 	Disconnect all connections and release all instance references.
 ]]
@@ -56,6 +79,9 @@ function InstanceMap:__fmtDebug(output)
 end
 
 function InstanceMap:insert(id, instance)
+	self:removeId(id)
+	self:removeInstance(instance)
+
 	self.fromIds[id] = instance
 	self.fromInstances[instance] = id
 	self:__connectSignals(instance)
@@ -68,8 +94,6 @@ function InstanceMap:removeId(id)
 		self:__disconnectSignals(instance)
 		self.fromIds[id] = nil
 		self.fromInstances[instance] = nil
-	else
-		Log.warn("Attempted to remove nonexistant ID {}", id)
 	end
 end
 
@@ -80,8 +104,6 @@ function InstanceMap:removeInstance(instance)
 	if id ~= nil then
 		self.fromInstances[instance] = nil
 		self.fromIds[id] = nil
-	else
-		Log.warn("Attempted to remove nonexistant instance {}", instance)
 	end
 end
 
@@ -89,10 +111,14 @@ function InstanceMap:destroyInstance(instance)
 	local id = self.fromInstances[instance]
 
 	if id ~= nil then
-		self:destroyId(id)
-	else
-		Log.warn("Attempted to destroy untracked instance {}", instance)
+		self:removeId(id)
 	end
+
+	for _, descendantInstance in ipairs(instance:GetDescendants()) do
+		self:removeInstance(descendantInstance)
+	end
+
+	instance:Destroy()
 end
 
 function InstanceMap:destroyId(id)
@@ -100,21 +126,37 @@ function InstanceMap:destroyId(id)
 	self:removeId(id)
 
 	if instance ~= nil then
-		local descendantsToDestroy = {}
-
-		for otherInstance in pairs(self.fromInstances) do
-			if otherInstance:IsDescendantOf(instance) then
-				table.insert(descendantsToDestroy, otherInstance)
-			end
-		end
-
-		for _, otherInstance in ipairs(descendantsToDestroy) do
-			self:removeInstance(otherInstance)
+		for _, descendantInstance in ipairs(instance:GetDescendants()) do
+			self:removeInstance(descendantInstance)
 		end
 
 		instance:Destroy()
+	end
+end
+
+--[[
+	Pause updates for an instance momentarily and invoke a callback.
+
+	If the callback throws an error, InstanceMap will still be kept in a
+	consistent state.
+]]
+function InstanceMap:pauseInstance(instance, callback)
+	local id = self.fromInstances[instance]
+
+	-- If we don't know about this instance, ignore it and do not invoke the
+	-- callback.
+	if id == nil then
+		return
+	end
+
+	self.pausedUpdateInstances[instance] = true
+	local success, result = xpcall(callback, debug.traceback)
+	self.pausedUpdateInstances[instance] = false
+
+	if success then
+		return result
 	else
-		Log.warn("Attempted to destroy nonexistant ID {}", id)
+		error(result, 2)
 	end
 end
 
@@ -150,9 +192,15 @@ end
 function InstanceMap:__maybeFireInstanceChanged(instance, propertyName)
 	Log.trace("{}.{} changed", instance:GetFullName(), propertyName)
 
-	if self.onInstanceChanged ~= nil then
-		self.onInstanceChanged(instance, propertyName)
+	if self.pausedUpdateInstances[instance] then
+		return
 	end
+
+	if self.onInstanceChanged == nil then
+		return
+	end
+
+	self.onInstanceChanged(instance, propertyName)
 end
 
 function InstanceMap:__disconnectSignals(instance)

plugin/src/PatchSet.lua

@@ -0,0 +1,184 @@
+--[[
+	Methods to operate on either a patch created by the hydrate method, or a
+	patch returned from the API.
+]]
+
+local t = require(script.Parent.Parent.t)
+
+local Types = require(script.Parent.Types)
+
+local PatchSet = {}
+
+PatchSet.validate = t.interface({
+	removed = t.array(t.union(Types.RbxId, t.Instance)),
+	added = t.map(Types.RbxId, Types.ApiInstance),
+	updated = t.array(Types.ApiInstanceUpdate),
+})
+
+--[[
+	Create a new, empty PatchSet.
+]]
+function PatchSet.newEmpty()
+	return {
+		removed = {},
+		added = {},
+		updated = {},
+	}
+end
+
+--[[
+	Tells whether the given PatchSet is empty.
+]]
+function PatchSet.isEmpty(patchSet)
+	return next(patchSet.removed) == nil and
+		next(patchSet.added) == nil and
+		next(patchSet.updated) == nil
+end
+
+--[[
+	Tells whether the given PatchSet has any remove operations.
+]]
+function PatchSet.hasRemoves(patchSet)
+	return next(patchSet.removed) ~= nil
+end
+
+--[[
+	Tells whether the given PatchSet has any add operations.
+]]
+function PatchSet.hasAdditions(patchSet)
+	return next(patchSet.added) ~= nil
+end
+
+--[[
+	Tells whether the given PatchSet has any update operations.
+]]
+function PatchSet.hasUpdates(patchSet)
+	return next(patchSet.updated) ~= nil
+end
+
+--[[
+	Merge multiple PatchSet objects into the given PatchSet.
+]]
+function PatchSet.assign(target, ...)
+	for i = 1, select("#", ...) do
+		local sourcePatch = select(i, ...)
+
+		for _, removed in ipairs(sourcePatch.removed) do
+			table.insert(target.removed, removed)
+		end
+
+		for id, added in pairs(sourcePatch.added) do
+			target.added[id] = added
+		end
+
+		for _, update in ipairs(sourcePatch.updated) do
+			table.insert(target.updated, update)
+		end
+	end
+
+	return target
+end
+
+--[[
+	Create a list of human-readable statements summarizing the contents of this
+	patch, intended to be displayed to users.
+]]
+function PatchSet.humanSummary(instanceMap, patchSet)
+	local statements = {}
+
+	for _, idOrInstance in ipairs(patchSet.removed) do
+		local instance, id
+
+		if type(idOrInstance) == "string" then
+			id = idOrInstance
+			instance = instanceMap.fromIds[id]
+		else
+			instance = idOrInstance
+			id = instanceMap.fromInstances[instance]
+		end
+
+		if instance ~= nil then
+			table.insert(statements, string.format("- Delete instance %s", instance:GetFullName()))
+		else
+			table.insert(statements, string.format("- Delete instance with ID %s", id))
+		end
+	end
+
+	local additionsMentioned = {}
+
+	local function addAllDescendents(virtualInstance)
+		additionsMentioned[virtualInstance.Id] = true
+
+		for _, childId in ipairs(virtualInstance.Children) do
+			addAllDescendents(patchSet.added[childId])
+		end
+	end
+
+	for id, addition in pairs(patchSet.added) do
+		if additionsMentioned[id] then
+			continue
+		end
+
+		local virtualInstance = addition
+		while true do
+			if virtualInstance.Parent == nil then
+				break
+			end
+
+			local virtualParent = patchSet.added[virtualInstance.Parent]
+			if virtualParent == nil then
+				break
+			end
+
+			virtualInstance = virtualParent
+		end
+
+		local parentDisplayName = "nil (how strange!)"
+		if virtualInstance.Parent ~= nil then
+			local parent = instanceMap.fromIds[virtualInstance.Parent]
+			if parent ~= nil then
+				parentDisplayName = parent:GetFullName()
+			end
+		end
+
+		table.insert(statements, string.format(
+			"- Add instance %q (ClassName %q) to %s",
+			virtualInstance.Name, virtualInstance.ClassName, parentDisplayName))
+	end
+
+	for _, update in ipairs(patchSet.updated) do
+		local updatedProperties = {}
+
+		if update.changedMetadata ~= nil then
+			table.insert(updatedProperties, "Rojo's Metadata")
+		end
+
+		if update.changedName ~= nil then
+			table.insert(updatedProperties, "Name")
+		end
+
+		if update.changedClassName ~= nil then
+			table.insert(updatedProperties, "ClassName")
+		end
+
+		for name in pairs(update.changedProperties) do
+			table.insert(updatedProperties, name)
+		end
+
+		local instance = instanceMap.fromIds[update.id]
+		local displayName
+		if instance ~= nil then
+			displayName = instance:GetFullName()
+		else
+			displayName = "[unknown instance]"
+		end
+
+		table.insert(statements, string.format(
+			"- Update properties on %s: %s",
+			displayName, table.concat(updatedProperties, ",")))
+	end
+
+	return table.concat(statements, "\n")
+end
+
+return PatchSet

plugin/src/Reconciler.lua

@@ -1,401 +0,0 @@
---[[
-	This module defines the meat of the Rojo plugin and how it manages tracking
-	and mutating the Roblox DOM.
-]]
-
-local RbxDom = require(script.Parent.Parent.RbxDom)
-local t = require(script.Parent.Parent.t)
-local Log = require(script.Parent.Parent.Log)
-
-local Types = require(script.Parent.Types)
-local invariant = require(script.Parent.invariant)
-local getCanonicalProperty = require(script.Parent.getCanonicalProperty)
-local setCanonicalProperty = require(script.Parent.setCanonicalProperty)
-
---[[
-	This interface represents either a patch created by the hydrate method, or a
-	patch returned from the API.
-
-	This type should be a subset of Types.ApiInstanceUpdate.
-]]
-local IPatch = t.interface({
-	removed = t.array(t.union(Types.RbxId, t.Instance)),
-	added = t.map(Types.RbxId, Types.ApiInstance),
-	updated = t.array(Types.ApiInstanceUpdate),
-})
-
---[[
-	Attempt to safely set the parent of an instance.
-
-	This function will always succeed, even if the actual set failed. This is
-	important for some types like services that will throw even if their current
-	parent is already set to the requested parent.
-
-	TODO: See if we can eliminate this by being more nuanced with property
-	assignment?
-]]
-local function safeSetParent(instance, newParent)
-	pcall(function()
-		instance.Parent = newParent
-	end)
-end
-
---[[
-	Similar to setting Parent, some instances really don't like being renamed.
-
-	TODO: Should we be throwing away these results or can we be more careful?
-]]
-local function safeSetName(instance, name)
-	pcall(function()
-		instance.Name = name
-	end)
-end
-
-local Reconciler = {}
-Reconciler.__index = Reconciler
-
-function Reconciler.new(instanceMap)
-	local self = {
-		-- Tracks all of the instances known by the reconciler by ID.
-		__instanceMap = instanceMap,
-	}
-
-	return setmetatable(self, Reconciler)
-end
-
---[[
-	See Reconciler:__hydrateInternal().
-]]
-function Reconciler:hydrate(apiInstances, id, instance)
-	local hydratePatch = {
-		removed = {},
-		added = {},
-		updated = {},
-	}
-
-	self:__hydrateInternal(apiInstances, id, instance, hydratePatch)
-
-	return hydratePatch
-end
-
---[[
-	Applies a patch to the Roblox DOM using the reconciler's internal state.
-
-	TODO: This function might only apply some of the patch in the future and
-	require content negotiation with the Rojo server to handle types that aren't
-	editable by scripts.
-]]
-local applyPatchSchema = Types.ifEnabled(t.tuple(
-	IPatch
-))
-function Reconciler:applyPatch(patch)
-	assert(applyPatchSchema(patch))
-
-	for _, removedIdOrInstance in ipairs(patch.removed) do
-		local removedInstance
-
-		if Types.RbxId(removedIdOrInstance) then
-			-- If this value is an ID, it's assumed to be an instance that the
-			-- Rojo server knows about.
-			removedInstance = self.__instanceMap.fromIds[removedIdOrInstance]
-			self.__instanceMap:removeId(removedIdOrInstance)
-		end
-
-		-- If this entry was an ID that we didn't know about, removedInstance
-		-- will be nil, which we guard against in case of minor tree desync.
-		if removedInstance ~= nil then
-			-- Ensure that if any descendants are tracked by Rojo, that we
-			-- properly un-track them.
-			for _, descendantInstance in ipairs(removedInstance:GetDescendants()) do
-				self.__instanceMap:removeInstance(descendantInstance)
-			end
-
-			removedInstance:Destroy()
-		end
-	end
-
-	-- TODO: This loop assumes that apiInstance.ParentId is never nil. The Rojo
-	-- plugin can't create a new top-level DataModel anyways, so this should
-	-- only be violated in cases that are already erroneous.
-	for id, apiInstance in pairs(patch.added) do
-		if self.__instanceMap.fromIds[id] == nil then
-			-- Find the first ancestor of this instance that is marked for an
-			-- addition.
-			--
-			-- This helps us make sure we only reify each instance once, and we
-			-- start from the top.
-			while patch.added[apiInstance.Parent] ~= nil do
-				id = apiInstance.Parent
-				apiInstance = patch.added[id]
-			end
-
-			local parentInstance = self.__instanceMap.fromIds[apiInstance.Parent]
-
-			if parentInstance == nil then
-				invariant(
-					"Cannot add an instance from a patch that has no parent.\nInstance {} with parent {}.\nState: {:#?}",
-					id,
-					apiInstance.Parent,
-					self.__instanceMap
-				)
-			end
-
-			self:__reifyInstance(patch.added, id, parentInstance)
-		end
-	end
-
-	for _, update in ipairs(patch.updated) do
-		local instance = self.__instanceMap.fromIds[update.id]
-
-		if instance == nil then
-			invariant(
-				"Cannot update an instance that does not exist in the reconciler's state.\nInstance {}\nState: {:#?}",
-				update.id,
-				self.__instanceMap
-			)
-		end
-
-		if update.changedClassName ~= nil then
-			error("TODO: Support changing class name by destroying + recreating instance.")
-		end
-
-		if update.changedName ~= nil then
-			instance.Name = update.changedName
-		end
-
-		if update.changedMetadata ~= nil then
-			print("TODO: Support changing metadata, if necessary.")
-		end
-
-		if update.changedProperties ~= nil then
-			for propertyName, propertyValue in pairs(update.changedProperties) do
-				-- TODO: Gracefully handle this error instead?
-				assert(setCanonicalProperty(instance, propertyName, self:__decodeApiValue(propertyValue)))
-			end
-		end
-	end
-end
-
---[[
-	Transforms a value into one that can be sent over the network back to the
-	Rojo server.
-
-	This operation can fail, and so it returns bool, value.
-]]
-function Reconciler:encodeApiValue(value)
-	if typeof(value) == "string" then
-		return true, {
-			Type = "String",
-			Value = value,
-		}
-	end
-
-	return false
-end
-
---[[
-	Transforms a value encoded by rbx_dom_weak on the server side into a value
-	usable by Rojo's reconciler, potentially using RbxDom.
-]]
-function Reconciler:__decodeApiValue(apiValue)
-	assert(Types.ApiValue(apiValue))
-
-	-- Refs are represented as IDs in the same space that Rojo's protocol uses.
-	if apiValue.Type == "Ref" then
-		-- TODO: This ref could be pointing at an instance we haven't created
-		-- yet!
-
-		return self.__instanceMap.fromIds[apiValue.Value]
-	end
-
-	local success, decodedValue = RbxDom.EncodedValue.decode(apiValue)
-
-	if not success then
-		error(decodedValue, 2)
-	end
-
-	return decodedValue
-end
-
---[[
-	Constructs an instance from an ApiInstance without any of its children.
-]]
-local reifySingleInstanceSchema = Types.ifEnabled(t.tuple(
-	Types.ApiInstance
-))
-function Reconciler:__reifySingleInstance(apiInstance)
-	assert(reifySingleInstanceSchema(apiInstance))
-
-	-- Instance.new can fail if we're passing in something that can't be
-	-- created, like a service, something enabled with a feature flag, or
-	-- something that requires higher security than we have.
-	local ok, instance = pcall(Instance.new, apiInstance.ClassName)
-	if not ok then
-		return false, instance
-	end
-
-	-- TODO: When can setting Name fail here?
-	safeSetName(instance, apiInstance.Name)
-
-	for key, value in pairs(apiInstance.Properties) do
-		setCanonicalProperty(instance, key, self:__decodeApiValue(value))
-	end
-
-	return true, instance
-end
-
---[[
-	Construct an instance and all of its descendants, parent it to the given
-	instance, and insert it into the reconciler's internal state.
-]]
-local reifyInstanceSchema = Types.ifEnabled(t.tuple(
-	t.map(Types.RbxId, Types.VirtualInstance),
-	Types.RbxId,
-	t.Instance
-))
-function Reconciler:__reifyInstance(apiInstances, id, parentInstance)
-	assert(reifyInstanceSchema(apiInstances, id, parentInstance))
-
-	local apiInstance = apiInstances[id]
-	local ok, instance = self:__reifySingleInstance(apiInstance)
-
-	-- TODO: Propagate this error upward to handle it elsewhere?
-	if not ok then
-		error(("Couldn't create an instance of type %q, a child of %s"):format(
-			apiInstance.ClassName,
-			parentInstance:GetFullName()
-		))
-	end
-
-	self.__instanceMap:insert(id, instance)
-
-	for _, childId in ipairs(apiInstance.Children) do
-		self:__reifyInstance(apiInstances, childId, instance)
-	end
-
-	safeSetParent(instance, parentInstance)
-
-	return instance
-end
-
---[[
-	Populates the reconciler's internal state, maps IDs to instances that the
-	Rojo plugin knows about, and generates a patch that would update the Roblox
-	tree to match Rojo's view of the tree.
-]]
-local hydrateSchema = Types.ifEnabled(t.tuple(
-	t.map(Types.RbxId, Types.VirtualInstance),
-	Types.RbxId,
-	t.Instance,
-	IPatch
-))
-function Reconciler:__hydrateInternal(apiInstances, id, instance, hydratePatch)
-	assert(hydrateSchema(apiInstances, id, instance, hydratePatch))
-
-	self.__instanceMap:insert(id, instance)
-
-	local apiInstance = apiInstances[id]
-
-	local function markIdAdded(id)
-		local apiInstance = apiInstances[id]
-		hydratePatch.added[id] = apiInstance
-
-		for _, childId in ipairs(apiInstance.Children) do
-			markIdAdded(childId)
-		end
-	end
-
-	local changedName = nil
-	local changedProperties = {}
-
-	if apiInstance.Name ~= instance.Name then
-		changedName = apiInstance.Name
-	end
-
-	for propertyName, virtualValue in pairs(apiInstance.Properties) do
-		local success, existingValue = getCanonicalProperty(instance, propertyName)
-
-		if success then
-			local decodedValue = self:__decodeApiValue(virtualValue)
-
-			if existingValue ~= decodedValue then
-				changedProperties[propertyName] = virtualValue
-			end
-		end
-	end
-
-	-- If any properties differed from the virtual instance we read, add it to
-	-- the hydrate patch so that we can catch up.
-	if changedName ~= nil or next(changedProperties) ~= nil then
-		table.insert(hydratePatch.updated, {
-			id = id,
-			changedName = changedName,
-			changedClassName = nil,
-			changedProperties = changedProperties,
-			changedMetadata = nil,
-		})
-	end
-
-	local existingChildren = instance:GetChildren()
-
-	-- For each existing child, we'll track whether it's been paired with an
-	-- instance that the Rojo server knows about.
-	local isExistingChildVisited = {}
-	for i = 1, #existingChildren do
-		isExistingChildVisited[i] = false
-	end
-
-	for _, childId in ipairs(apiInstance.Children) do
-		local apiChild = apiInstances[childId]
-
-		local childInstance
-
-		for childIndex, instance in ipairs(existingChildren) do
-			if not isExistingChildVisited[childIndex] then
-				-- We guard accessing Name and ClassName in order to avoid
-				-- tripping over children of DataModel that Rojo won't have
-				-- permissions to access at all.
-				local ok, name, className = pcall(function()
-					return instance.Name, instance.ClassName
-				end)
-
-				-- This rule is very conservative and could be loosened in the
-				-- future, or more heuristics could be introduced.
-				if ok and name == apiChild.Name and className == apiChild.ClassName then
-					childInstance = instance
-					isExistingChildVisited[childIndex] = true
-					break
-				end
-			end
-		end
-
-		if childInstance ~= nil then
-			-- We found an instance that matches the instance from the API, yay!
-			self:__hydrateInternal(apiInstances, childId, childInstance, hydratePatch)
-		else
-			markIdAdded(childId)
-		end
-	end
-
-	-- Any unvisited children at this point aren't known by Rojo and we can
-	-- destroy them unless the user has explicitly asked us to preserve children
-	-- of this instance.
-	local shouldClearUnknown = self:__shouldClearUnknownChildren(apiInstance)
-	if shouldClearUnknown then
-		for childIndex, visited in ipairs(isExistingChildVisited) do
-			if not visited then
-				table.insert(hydratePatch.removed, existingChildren[childIndex])
-			end
-		end
-	end
-end
-
-function Reconciler:__shouldClearUnknownChildren(apiInstance)
-	if apiInstance.Metadata ~= nil then
-		return not apiInstance.Metadata.ignoreUnknownInstances
-	else
-		return true
-	end
-end
-
-return Reconciler

plugin/src/Reconciler/Error.lua

@@ -0,0 +1,37 @@
+--[[
+	Defines the errors that can be returned by the reconciler.
+]]
+
+local Fmt = require(script.Parent.Parent.Parent.Fmt)
+
+local Error = {}
+
+local function makeVariant(name)
+	Error[name] = setmetatable({}, {
+		__tostring = function()
+			return "Error." .. name
+		end,
+	})
+end
+
+makeVariant("CannotCreateInstance")
+makeVariant("CannotDecodeValue")
+makeVariant("LackingPropertyPermissions")
+makeVariant("OtherPropertyError")
+makeVariant("RefDidNotExist")
+makeVariant("UnknownProperty")
+makeVariant("UnreadableProperty")
+makeVariant("UnwritableProperty")
+
+function Error.new(kind, details)
+	return setmetatable({
+		kind = kind,
+		details = details,
+	}, Error)
+end
+
+function Error:__tostring()
+	return Fmt.fmt("Error({}): {:#?}", self.kind, self.details)
+end
+
+return Error

plugin/src/Reconciler/applyPatch.lua

@@ -0,0 +1,200 @@
+--[[
+	Apply a patch to the DOM. Returns any portions of the patch that weren't
+	possible to apply.
+
+	Patches can come from the server or be generated by the client.
+]]
+
+local Log = require(script.Parent.Parent.Parent.Log)
+
+local PatchSet = require(script.Parent.Parent.PatchSet)
+local Types = require(script.Parent.Parent.Types)
+local invariant = require(script.Parent.Parent.invariant)
+
+local decodeValue = require(script.Parent.decodeValue)
+local reify = require(script.Parent.reify)
+local setProperty = require(script.Parent.setProperty)
+
+local function applyPatch(instanceMap, patch)
+	-- Tracks any portions of the patch that could not be applied to the DOM.
+	local unappliedPatch = PatchSet.newEmpty()
+
+	for _, removedIdOrInstance in ipairs(patch.removed) do
+		if Types.RbxId(removedIdOrInstance) then
+			instanceMap:destroyId(removedIdOrInstance)
+		else
+			instanceMap:destroyInstance(removedIdOrInstance)
+		end
+	end
+
+	for id, virtualInstance in pairs(patch.added) do
+		if instanceMap.fromIds[id] ~= nil then
+			-- This instance already exists. We might've already added it in a
+			-- previous iteration of this loop, or maybe this patch was not
+			-- supposed to list this instance.
+			--
+			-- It's probably fine, right?
+			continue
+		end
+
+		-- Find the first ancestor of this instance that is marked for an
+		-- addition.
+		--
+		-- This helps us make sure we only reify each instance once, and we
+		-- start from the top.
+		while patch.added[virtualInstance.Parent] ~= nil do
+			id = virtualInstance.Parent
+			virtualInstance = patch.added[id]
+		end
+
+		local parentInstance = instanceMap.fromIds[virtualInstance.Parent]
+
+		if parentInstance == nil then
+			-- This would be peculiar. If you create an instance with no
+			-- parent, were you supposed to create it at all?
+			invariant(
+				"Cannot add an instance from a patch that has no parent.\nInstance {} with parent {}.\nState: {:#?}",
+				id,
+				virtualInstance.Parent,
+				instanceMap
+			)
+		end
+
+		local failedToReify = reify(instanceMap, patch.added, id, parentInstance)
+
+		if not PatchSet.isEmpty(failedToReify) then
+			Log.debug("Failed to reify as part of applying a patch: {}", failedToReify)
+			PatchSet.assign(unappliedPatch, failedToReify)
+		end
+	end
+
+	for _, update in ipairs(patch.updated) do
+		local instance = instanceMap.fromIds[update.id]
+
+		if instance == nil then
+			-- We can't update an instance that doesn't exist.
+			table.insert(unappliedPatch.updated, update)
+			continue
+		end
+
+		-- Track any part of this update that could not be applied.
+		local unappliedUpdate = {
+			id = update.id,
+			changedProperties = {},
+		}
+		local partiallyApplied = false
+
+		-- If the instance's className changed, we have a bumpy ride ahead while
+		-- we recreate this instance and move all of its children into the new
+		-- version atomically...ish.
+		if update.changedClassName ~= nil then
+			-- If the instance's name also changed, we'll do it here, since this
+			-- branch will skip the rest of the loop iteration.
+			local newName = update.changedName or instance.Name
+
+			-- TODO: When changing between instances that have similar sets of
+			-- properties, like between an ImageLabel and an ImageButton, we
+			-- should preserve all of the properties that are shared between the
+			-- two classes unless they're changed as part of this patch. This is
+			-- similar to how "class changer" Studio plugins work.
+			--
+			-- For now, we'll only apply properties that are mentioned in this
+			-- update. Patches with changedClassName set only occur in specific
+			-- circumstances, usually between Folder and ModuleScript instances.
+			-- While this may result in some issues, like not preserving the
+			-- "Archived" property, a robust solution is sufficiently
+			-- complicated that we're pushing it off for now.
+			local newProperties = update.changedProperties
+
+			-- If the instance's ClassName changed, we'll kick into reify to
+			-- create this instance. We'll handle moving all of children between
+			-- the instances after the new one is created.
+			local mockVirtualInstance = {
+				Id = update.id,
+				Name = newName,
+				ClassName = update.changedClassName,
+				Properties = newProperties,
+				Children = {},
+			}
+
+			local mockAdded = {
+				[update.id] = mockVirtualInstance,
+			}
+
+			local failedToReify = reify(instanceMap, mockAdded, update.id, instance.Parent)
+
+			local newInstance = instanceMap.fromIds[update.id]
+
+			-- Some parts of reify may have failed, but this is not necessarily
+			-- critical. If the instance wasn't recreated or has the wrong Name,
+			-- we'll consider our attempt a failure.
+			if instance == newInstance or newInstance.Name ~= newName then
+				table.insert(unappliedPatch.updated, update)
+				continue
+			end
+
+			-- Here are the non-critical failures. We know that the instance
+			-- succeeded in creating and that assigning Name did not fail, but
+			-- other property assignments might've failed.
+			if not PatchSet.isEmpty(failedToReify) then
+				PatchSet.assign(unappliedPatch, failedToReify)
+			end
+
+			-- Watch out, this is the scary part! Move all of the children of
+			-- instance into newInstance.
+			--
+			-- TODO: If this fails part way through, should we move everything
+			-- back? For now, we assume that moving things will not fail.
+			for _, child in ipairs(instance:GetChildren()) do
+				child.Parent = newInstance
+			end
+
+			-- See you later, original instance.
+			--
+			-- TODO: Can this fail? Some kinds of instance may not appreciate
+			-- being destroyed, like services.
+			instance:Destroy()
+
+			-- This completes your rebuilding a plane mid-flight safety
+			-- instruction. Please sit back, relax, and enjoy your flight.
+			continue
+		end
+
+		if update.changedName ~= nil then
+			instance.Name = update.changedName
+		end
+
+		if update.changedMetadata ~= nil then
+			-- TODO: Support changing metadata. This will become necessary when
+			-- Rojo persistently tracks metadata for each instance in order to
+			-- remove extra instances.
+			unappliedUpdate.changedMetadata = update.changedMetadata
+			partiallyApplied = true
+		end
+
+		if update.changedProperties ~= nil then
+			for propertyName, propertyValue in pairs(update.changedProperties) do
+				local ok, decodedValue = decodeValue(propertyValue, instanceMap)
+				if not ok then
+					unappliedUpdate.changedProperties[propertyName] = propertyValue
+					partiallyApplied = true
+					continue
+				end
+
+				local ok = setProperty(instance, propertyName, decodedValue)
+				if not ok then
+					unappliedUpdate.changedProperties[propertyName] = propertyValue
+					partiallyApplied = true
+				end
+			end
+		end
+
+		if partiallyApplied then
+			table.insert(unappliedPatch.updated, unappliedUpdate)
+		end
+	end
+
+	return unappliedPatch
+end
+
+return applyPatch

plugin/src/Reconciler/applyPatch.spec.lua

@@ -0,0 +1,198 @@
+return function()
+	local applyPatch = require(script.Parent.applyPatch)
+
+	local InstanceMap = require(script.Parent.Parent.InstanceMap)
+	local PatchSet = require(script.Parent.Parent.PatchSet)
+
+	local dummy = Instance.new("Folder")
+	local function wasDestroyed(instance)
+		-- If an instance was destroyed, its parent property is locked.
+		local ok = pcall(function()
+			local oldParent = instance.Parent
+			instance.Parent = dummy
+			instance.Parent = oldParent
+		end)
+
+		return not ok
+	end
+
+	it("should return an empty patch if given an empty patch", function()
+		local patch = applyPatch(InstanceMap.new(), PatchSet.newEmpty())
+		assert(PatchSet.isEmpty(patch), "expected remaining patch to be empty")
+	end)
+
+	it("should destroy instances listed for remove", function()
+		local root = Instance.new("Folder")
+
+		local child = Instance.new("Folder")
+		child.Name = "Child"
+		child.Parent = root
+
+		local instanceMap = InstanceMap.new()
+		instanceMap:insert("ROOT", root)
+		instanceMap:insert("CHILD", child)
+
+		local patch = PatchSet.newEmpty()
+		table.insert(patch.removed, child)
+
+		local unapplied = applyPatch(instanceMap, patch)
+		assert(PatchSet.isEmpty(unapplied), "expected remaining patch to be empty")
+
+		assert(not wasDestroyed(root), "expected root to be left alone")
+		assert(wasDestroyed(child), "expected child to be destroyed")
+
+		instanceMap:stop()
+	end)
+
+	it("should destroy IDs listed for remove", function()
+		local root = Instance.new("Folder")
+
+		local child = Instance.new("Folder")
+		child.Name = "Child"
+		child.Parent = root
+
+		local instanceMap = InstanceMap.new()
+		instanceMap:insert("ROOT", root)
+		instanceMap:insert("CHILD", child)
+
+		local patch = PatchSet.newEmpty()
+		table.insert(patch.removed, "CHILD")
+
+		local unapplied = applyPatch(instanceMap, patch)
+		assert(PatchSet.isEmpty(unapplied), "expected remaining patch to be empty")
+		expect(instanceMap:size()).to.equal(1)
+
+		assert(not wasDestroyed(root), "expected root to be left alone")
+		assert(wasDestroyed(child), "expected child to be destroyed")
+
+		instanceMap:stop()
+	end)
+
+	it("should add instances to the DOM", function()
+		-- Many of the details of this functionality are instead covered by
+		-- tests on reify, not here.
+
+		local root = Instance.new("Folder")
+
+		local instanceMap = InstanceMap.new()
+		instanceMap:insert("ROOT", root)
+
+		local patch = PatchSet.newEmpty()
+		patch.added["CHILD"] = {
+			Id = "CHILD",
+			ClassName = "Model",
+			Name = "Child",
+			Parent = "ROOT",
+			Children = {"GRANDCHILD"},
+			Properties = {},
+		}
+
+		patch.added["GRANDCHILD"]  = {
+			Id = "GRANDCHILD",
+			ClassName = "Part",
+			Name = "Grandchild",
+			Parent = "CHILD",
+			Children = {},
+			Properties = {},
+		}
+
+		local unapplied = applyPatch(instanceMap, patch)
+		assert(PatchSet.isEmpty(unapplied), "expected remaining patch to be empty")
+		expect(instanceMap:size()).to.equal(3)
+
+		local child = root:FindFirstChild("Child")
+		expect(child).to.be.ok()
+		expect(child.ClassName).to.equal("Model")
+		expect(child).to.equal(instanceMap.fromIds["CHILD"])
+
+		local grandchild = child:FindFirstChild("Grandchild")
+		expect(grandchild).to.be.ok()
+		expect(grandchild.ClassName).to.equal("Part")
+		expect(grandchild).to.equal(instanceMap.fromIds["GRANDCHILD"])
+	end)
+
+	it("should return unapplied additions when instances cannot be created", function()
+		local root = Instance.new("Folder")
+
+		local instanceMap = InstanceMap.new()
+		instanceMap:insert("ROOT", root)
+
+		local patch = PatchSet.newEmpty()
+		patch.added["OOPSIE"] = {
+			Id = "OOPSIE",
+			-- Hopefully Roblox never makes an instance with this ClassName.
+			ClassName = "UH OH",
+			Name = "FUBAR",
+			Parent = "ROOT",
+			Children = {},
+			Properties = {},
+		}
+
+		local unapplied = applyPatch(instanceMap, patch)
+		expect(unapplied.added["OOPSIE"]).to.equal(patch.added["OOPSIE"])
+		expect(instanceMap:size()).to.equal(1)
+		expect(#root:GetChildren()).to.equal(0)
+	end)
+
+	it("should apply property changes to instances", function()
+		local value = Instance.new("StringValue")
+		value.Value = "HELLO"
+
+		local instanceMap = InstanceMap.new()
+		instanceMap:insert("VALUE", value)
+
+		local patch = PatchSet.newEmpty()
+		table.insert(patch.updated, {
+			id = "VALUE",
+			changedProperties = {
+				Value = {
+					Type = "String",
+					Value = "WORLD",
+				},
+			},
+		})
+
+		local unapplied = applyPatch(instanceMap, patch)
+		assert(PatchSet.isEmpty(unapplied), "expected remaining patch to be empty")
+		expect(value.Value).to.equal("WORLD")
+	end)
+
+	it("should recreate instances when changedClassName is set, preserving children", function()
+		local root = Instance.new("Folder")
+		root.Name = "Initial Root Name"
+
+		local child = Instance.new("Folder")
+		child.Name = "Child"
+		child.Parent = root
+
+		local instanceMap = InstanceMap.new()
+		instanceMap:insert("ROOT", root)
+		instanceMap:insert("CHILD", child)
+
+		local patch = PatchSet.newEmpty()
+		table.insert(patch.updated, {
+			id = "ROOT",
+			changedName = "Updated Root Name",
+			changedClassName = "StringValue",
+			changedProperties = {
+				Value = {
+					Type = "String",
+					Value = "I am Root",
+				},
+			},
+		})
+
+		local unapplied = applyPatch(instanceMap, patch)
+		assert(PatchSet.isEmpty(unapplied), "expected remaining patch to be empty")
+
+		local newRoot = instanceMap.fromIds["ROOT"]
+		assert(newRoot ~= root, "expected instance to be recreated")
+		expect(newRoot.ClassName).to.equal("StringValue")
+		expect(newRoot.Name).to.equal("Updated Root Name")
+		expect(newRoot.Value).to.equal("I am Root")
+
+		local newChild = newRoot:FindFirstChild("Child")
+		assert(newChild ~= nil, "expected child to be present")
+		assert(newChild == child, "expected child to be preserved")
+	end)
+end

plugin/src/Reconciler/decodeValue.lua

@@ -0,0 +1,35 @@
+--[[
+	Transforms a value encoded by rbx_dom_weak on the server side into a value
+	usable by Rojo's reconciler, potentially using RbxDom.
+]]
+
+local RbxDom = require(script.Parent.Parent.Parent.RbxDom)
+local Error = require(script.Parent.Error)
+
+local function decodeValue(virtualValue, instanceMap)
+	-- Refs are represented as IDs in the same space that Rojo's protocol uses.
+	if virtualValue.Type == "Ref" then
+		local instance = instanceMap.fromIds[virtualValue.Value]
+
+		if instance ~= nil then
+			return true, instance
+		else
+			return false, Error.new(Error.RefDidNotExist, {
+				virtualValue = virtualValue,
+			})
+		end
+	end
+
+	local ok, decodedValue = RbxDom.EncodedValue.decode(virtualValue)
+
+	if not ok then
+		return false, Error.new(Error.CannotDecodeValue, {
+			virtualValue = virtualValue,
+			innerError = decodedValue,
+		})
+	end
+
+	return true, decodedValue
+end
+
+return decodeValue

plugin/src/Reconciler/diff.lua

@@ -0,0 +1,148 @@
+--[[
+	Defines the process for diffing a virtual DOM and the real DOM to compute a
+	patch that can be later applied.
+]]
+
+local Log = require(script.Parent.Parent.Parent.Log)
+local invariant = require(script.Parent.Parent.invariant)
+local getProperty = require(script.Parent.getProperty)
+local Error = require(script.Parent.Error)
+local decodeValue = require(script.Parent.decodeValue)
+
+local function isEmpty(table)
+	return next(table) == nil
+end
+
+local function shouldDeleteUnknownInstances(virtualInstance)
+	if virtualInstance.Metadata ~= nil then
+		return not virtualInstance.Metadata.ignoreUnknownInstances
+	else
+		return true
+	end
+end
+
+local function diff(instanceMap, virtualInstances, rootId)
+	local patch = {
+		removed = {},
+		added = {},
+		updated = {},
+	}
+
+	-- Add a virtual instance and all of its descendants to the patch, marked as
+	-- being added.
+	local function markIdAdded(id)
+		local virtualInstance = virtualInstances[id]
+		patch.added[id] = virtualInstance
+
+		for _, childId in ipairs(virtualInstance.Children) do
+			markIdAdded(childId)
+		end
+	end
+
+	-- Internal recursive kernel for diffing an instance with the given ID.
+	local function diffInternal(id)
+		local virtualInstance = virtualInstances[id]
+		local instance = instanceMap.fromIds[id]
+
+		if virtualInstance == nil then
+			invariant("Cannot diff an instance not present in virtualInstances\nID: {}", id)
+		end
+
+		if instance == nil then
+			invariant("Cannot diff an instance not present in InstanceMap\nID: {}", id)
+		end
+
+		if virtualInstance.ClassName ~= instance.ClassName then
+			error("unimplemented: support changing ClassName")
+		end
+
+		local changedName = nil
+		if virtualInstance.Name ~= instance.Name then
+			changedName = virtualInstance.Name
+		end
+
+		local changedProperties = {}
+		for propertyName, virtualValue in pairs(virtualInstance.Properties) do
+			local ok, existingValueOrErr = getProperty(instance, propertyName)
+
+			if ok then
+				local existingValue = existingValueOrErr
+				local ok, decodedValue = decodeValue(virtualValue, instanceMap)
+
+				if ok then
+					if existingValue ~= decodedValue then
+						changedProperties[propertyName] = virtualValue
+					end
+				else
+					Log.warn("Failed to decode property of type {}", virtualValue.Type)
+				end
+			else
+				local err = existingValueOrErr
+
+				if err.kind == Error.UnknownProperty then
+					Log.trace("Skipping unknown property {}.{}", err.details.className, err.details.propertyName)
+				elseif err.kind == Error.UnreadableProperty then
+					Log.trace("Skipping unreadable property {}.{}", err.details.className, err.details.propertyName)
+				else
+					return false, err
+				end
+			end
+		end
+
+		if changedName ~= nil or not isEmpty(changedProperties) then
+			table.insert(patch.updated, {
+				id = id,
+				changedName = changedName,
+				changedClassName = nil,
+				changedProperties = changedProperties,
+				changedMetadata = nil,
+			})
+		end
+
+		-- Traverse the list of children in the DOM. Any instance that has no
+		-- corresponding virtual instance should be removed. Any instance that
+		-- does have a corresponding virtual instance is recursively diffed.
+		for _, childInstance in ipairs(instance:GetChildren()) do
+			local childId = instanceMap.fromInstances[childInstance]
+
+			if childId == nil then
+				-- This is an existing instance not present in the virtual DOM.
+				-- We can mark it for deletion unless the user has asked us not
+				-- to delete unknown stuff.
+				if shouldDeleteUnknownInstances(virtualInstance) then
+					table.insert(patch.removed, childInstance)
+				end
+			else
+				local ok, err = diffInternal(childId)
+
+				if not ok then
+					return false, err
+				end
+			end
+		end
+
+		-- Traverse the list of children in the virtual DOM. Any virtual
+		-- instance that has no corresponding real instance should be created.
+		for _, childId in ipairs(virtualInstance.Children) do
+			local childInstance = instanceMap.fromIds[childId]
+
+			if childInstance == nil then
+				-- This instance is present in the virtual DOM, but doesn't
+				-- exist in the real DOM.
+				markIdAdded(childId)
+			end
+		end
+
+		return true
+	end
+
+	local ok, err = diffInternal(rootId)
+
+	if not ok then
+		return false, err
+	end
+
+	return true, patch
+end
+
+return diff

plugin/src/Reconciler/diff.spec.lua

@@ -0,0 +1,292 @@
+return function()
+	local Log = require(script.Parent.Parent.Parent.Log)
+
+	local InstanceMap = require(script.Parent.Parent.InstanceMap)
+	local PatchSet = require(script.Parent.Parent.PatchSet)
+
+	local diff = require(script.Parent.diff)
+
+	local function isEmpty(table)
+		return next(table) == nil, "Table was not empty"
+	end
+
+	local function size(dict)
+		local len = 0
+
+		for _ in pairs(dict) do
+			len = len + 1
+		end
+
+		return len
+	end
+
+	it("should generate an empty patch for empty instances", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Some Name",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("Folder")
+		rootInstance.Name = "Some Name"
+		knownInstances:insert("ROOT", rootInstance)
+
+		local ok, patch = diff(knownInstances, virtualInstances, "ROOT")
+
+		assert(ok, tostring(patch))
+
+		assert(isEmpty(patch.removed))
+		assert(isEmpty(patch.added))
+		assert(isEmpty(patch.updated))
+	end)
+
+	it("should generate a patch with a changed name", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Some Name",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("Folder")
+		knownInstances:insert("ROOT", rootInstance)
+
+		local ok, patch = diff(knownInstances, virtualInstances, "ROOT")
+
+		assert(ok, tostring(patch))
+
+		assert(isEmpty(patch.removed))
+		assert(isEmpty(patch.added))
+		expect(#patch.updated).to.equal(1)
+
+		local update = patch.updated[1]
+		expect(update.id).to.equal("ROOT")
+		expect(update.changedName).to.equal("Some Name")
+		assert(isEmpty(update.changedProperties))
+	end)
+
+	it("should generate a patch with a changed property", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "StringValue",
+				Name = "Value",
+				Properties = {
+					Value = {
+						Type = "String",
+						Value = "Hello, world!",
+					},
+				},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("StringValue")
+		rootInstance.Value = "Initial Value"
+		knownInstances:insert("ROOT", rootInstance)
+
+		local ok, patch = diff(knownInstances, virtualInstances, "ROOT")
+
+		assert(ok, tostring(patch))
+
+		assert(isEmpty(patch.removed))
+		assert(isEmpty(patch.added))
+		expect(#patch.updated).to.equal(1)
+
+		local update = patch.updated[1]
+		expect(update.id).to.equal("ROOT")
+		expect(update.changedName).to.equal(nil)
+		expect(size(update.changedProperties)).to.equal(1)
+
+		local patchProperty = update.changedProperties["Value"]
+		expect(patchProperty).to.be.a("table")
+		expect(patchProperty.Type).to.equal("String")
+		expect(patchProperty.Value).to.equal("Hello, world!")
+	end)
+
+	it("should generate an empty patch if no properties changed", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "StringValue",
+				Name = "Value",
+				Properties = {
+					Value = {
+						Type = "String",
+						Value = "Hello, world!",
+					},
+				},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("StringValue")
+		rootInstance.Value = "Hello, world!"
+		knownInstances:insert("ROOT", rootInstance)
+
+		local ok, patch = diff(knownInstances, virtualInstances, "ROOT")
+
+		assert(ok, tostring(patch))
+		assert(PatchSet.isEmpty(patch), "expected empty patch")
+	end)
+
+	it("should ignore unknown properties", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Folder",
+				Properties = {
+					FAKE_PROPERTY = {
+						Type = "String",
+						Value = "Hello, world!",
+					},
+				},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("Folder")
+		knownInstances:insert("ROOT", rootInstance)
+
+		local ok, patch = diff(knownInstances, virtualInstances, "ROOT")
+
+		assert(ok, tostring(patch))
+
+		assert(isEmpty(patch.removed))
+		assert(isEmpty(patch.added))
+		assert(isEmpty(patch.updated))
+	end)
+
+	--[[
+		Because rbx_dom_lua resolves non-canonical properties to their canonical
+		variants, this test does not work as intended.
+
+		Instead, heat_xml is diffed with Heat, the canonical property variant,
+		and a patch trying to assign to heat_xml is generated. This is
+		incorrect, but will require more invasive changes to fix later.
+	]]
+	itFIXME("should ignore unreadable properties", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Fire",
+				Name = "Fire",
+				Properties = {
+					-- heat_xml is a serialization-only property that is not
+					-- exposed to Lua.
+					heat_xml = {
+						Type = "Float32",
+						Value = 5,
+					},
+				},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("Fire")
+		knownInstances:insert("ROOT", rootInstance)
+
+		local ok, patch = diff(knownInstances, virtualInstances, "ROOT")
+
+		Log.warn("{:#?}", patch)
+
+		assert(ok, tostring(patch))
+
+		assert(isEmpty(patch.removed))
+		assert(isEmpty(patch.added))
+		assert(isEmpty(patch.updated))
+	end)
+
+	it("should generate a patch removing unknown children by default", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Folder",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("Folder")
+		local unknownChild = Instance.new("Folder")
+		unknownChild.Parent = rootInstance
+		knownInstances:insert("ROOT", rootInstance)
+
+		local ok, patch = diff(knownInstances, virtualInstances, "ROOT")
+
+		assert(ok, tostring(patch))
+
+		assert(isEmpty(patch.added))
+		assert(isEmpty(patch.updated))
+		expect(#patch.removed).to.equal(1)
+		expect(patch.removed[1]).to.equal(unknownChild)
+	end)
+
+	it("should generate an empty patch if unknown children should be ignored", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Folder",
+				Properties = {},
+				Children = {},
+				Metadata = {
+					ignoreUnknownInstances = true,
+				},
+			},
+		}
+
+		local rootInstance = Instance.new("Folder")
+		local unknownChild = Instance.new("Folder")
+		unknownChild.Parent = rootInstance
+		knownInstances:insert("ROOT", rootInstance)
+
+		local ok, patch = diff(knownInstances, virtualInstances, "ROOT")
+
+		assert(ok, tostring(patch))
+
+		assert(isEmpty(patch.added))
+		assert(isEmpty(patch.updated))
+		assert(isEmpty(patch.removed))
+	end)
+
+	it("should generate a patch with an added child", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Folder",
+				Properties = {},
+				Children = {"CHILD"},
+			},
+
+			CHILD = {
+				ClassName = "Folder",
+				Name = "Child",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("Folder")
+		knownInstances:insert("ROOT", rootInstance)
+
+		local ok, patch = diff(knownInstances, virtualInstances, "ROOT")
+
+		assert(ok, tostring(patch))
+
+		assert(isEmpty(patch.updated))
+		assert(isEmpty(patch.removed))
+		expect(size(patch.added)).to.equal(1)
+		expect(patch.added["CHILD"]).to.equal(virtualInstances["CHILD"])
+	end)
+end

plugin/src/Reconciler/getProperty.lua

@@ -1,9 +1,11 @@
-local RbxDom = require(script.Parent.Parent.RbxDom)
-
 --[[
-	Attempts to set a property on the given instance.
+	Attempts to read a property from the given instance.
 ]]
-local function getCanonincalProperty(instance, propertyName)
+
+local RbxDom = require(script.Parent.Parent.Parent.RbxDom)
+local Error = require(script.Parent.Error)
+
+local function getProperty(instance, propertyName)
 	local descriptor = RbxDom.findCanonicalPropertyDescriptor(instance.ClassName, propertyName)
 
 	-- We can skip unknown properties; they're not likely reflected to Lua.
@@ -11,11 +13,17 @@ local function getCanonincalProperty(instance, propertyName)
 	-- A good example of a property like this is `Model.ModelInPrimary`, which
 	-- is serialized but not reflected to Lua.
 	if descriptor == nil then
-		return false, "unknown property"
+		return false, Error.new(Error.UnknownProperty, {
+			className = instance.ClassName,
+			propertyName = propertyName,
+		})
 	end
 
 	if descriptor.scriptability == "None" or descriptor.scriptability == "Write" then
-		return false, "unreadable property"
+		return false, Error.new(Error.UnreadableProperty, {
+			className = instance.ClassName,
+			propertyName = propertyName,
+		})
 	end
 
 	local success, valueOrErr = descriptor:read(instance)
@@ -26,14 +34,19 @@ local function getCanonincalProperty(instance, propertyName)
 		-- If we don't have permission to read a property, we can chalk that up
 		-- to our database being out of date and the engine being right.
 		if err.kind == RbxDom.Error.Kind.Roblox and err.extra:find("lacking permission") then
-			return false, "permission error"
+			return false, Error.new(Error.LackingPropertyPermissions, {
+				className = instance.ClassName,
+				propertyName = propertyName,
+			})
 		end
 
-		local message = ("Invalid property %s.%s: %s"):format(descriptor.className, descriptor.name, tostring(err))
-		error(message, 2)
+		return false, Error.new(Error.OtherPropertyError, {
+			className = instance.ClassName,
+			propertyName = propertyName,
+		})
 	end
 
 	return true, valueOrErr
 end
 
-return getCanonincalProperty
+return getProperty

plugin/src/Reconciler/hydrate.lua

@@ -0,0 +1,50 @@
+--[[
+	Defines the process of "hydration" -- matching up a virtual DOM with
+	concrete instances and assigning them IDs.
+]]
+
+local invariant = require(script.Parent.Parent.invariant)
+
+local function hydrate(instanceMap, virtualInstances, rootId, rootInstance)
+	local virtualInstance = virtualInstances[rootId]
+
+	if virtualInstance == nil then
+		invariant("Cannot hydrate an instance not present in virtualInstances\nID: {}", rootId)
+	end
+
+	instanceMap:insert(rootId, rootInstance)
+
+	local existingChildren = rootInstance:GetChildren()
+
+	-- For each existing child, we'll track whether it's been paired with an
+	-- instance that the Rojo server knows about.
+	local isExistingChildVisited = {}
+	for i = 1, #existingChildren do
+		isExistingChildVisited[i] = false
+	end
+
+	for _, childId in ipairs(virtualInstance.Children) do
+		local virtualChild = virtualInstances[childId]
+
+		for childIndex, childInstance in ipairs(existingChildren) do
+			if not isExistingChildVisited[childIndex] then
+				-- We guard accessing Name and ClassName in order to avoid
+				-- tripping over children of DataModel that Rojo won't have
+				-- permissions to access at all.
+				local ok, name, className = pcall(function()
+					return childInstance.Name, childInstance.ClassName
+				end)
+
+				-- This rule is very conservative and could be loosened in the
+				-- future, or more heuristics could be introduced.
+				if ok and name == virtualChild.Name and className == virtualChild.ClassName then
+					isExistingChildVisited[childIndex] = true
+					hydrate(instanceMap, virtualInstances, childId, childInstance)
+					break
+				end
+			end
+		end
+	end
+end
+
+return hydrate

plugin/src/Reconciler/hydrate.spec.lua

@@ -0,0 +1,129 @@
+return function()
+	local hydrate = require(script.Parent.hydrate)
+
+	local InstanceMap = require(script.Parent.Parent.InstanceMap)
+
+	it("should match the root instance no matter what", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Model",
+				Name = "Foo",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("Folder")
+
+		hydrate(knownInstances, virtualInstances, "ROOT", rootInstance)
+
+		expect(knownInstances:size()).to.equal(1)
+		expect(knownInstances.fromIds["ROOT"]).to.equal(rootInstance)
+	end)
+
+	it("should not match children with mismatched ClassName", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Root",
+				Properties = {},
+				Children = {},
+			},
+
+			CHILD = {
+				ClassName = "Folder",
+				Name = "Child",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("Folder")
+
+		-- ClassName of this instance is intentionally different
+		local child = Instance.new("Model")
+		child.Name = "Child"
+		child.Parent = rootInstance
+
+		hydrate(knownInstances, virtualInstances, "ROOT", rootInstance)
+
+		expect(knownInstances:size()).to.equal(1)
+		expect(knownInstances.fromIds["ROOT"]).to.equal(rootInstance)
+	end)
+
+	it("should not match children with mismatched Name", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Root",
+				Properties = {},
+				Children = {},
+			},
+
+			CHILD = {
+				ClassName = "Folder",
+				Name = "Child",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("Folder")
+
+		-- Name of this instance is intentionally different
+		local child = Instance.new("Folder")
+		child.Name = "Not Child"
+		child.Parent = rootInstance
+
+		hydrate(knownInstances, virtualInstances, "ROOT", rootInstance)
+
+		expect(knownInstances:size()).to.equal(1)
+		expect(knownInstances.fromIds["ROOT"]).to.equal(rootInstance)
+	end)
+
+	it("should pair instances with matching Name and ClassName", function()
+		local knownInstances = InstanceMap.new()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Root",
+				Properties = {},
+				Children = {"CHILD1", "CHILD2"},
+			},
+
+			CHILD1 = {
+				ClassName = "Folder",
+				Name = "Child 1",
+				Properties = {},
+				Children = {},
+			},
+
+			CHILD2 = {
+				ClassName = "Model",
+				Name = "Child 2",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local rootInstance = Instance.new("Folder")
+
+		local child1 = Instance.new("Folder")
+		child1.Name = "Child 1"
+		child1.Parent = rootInstance
+
+		local child2 = Instance.new("Model")
+		child2.Name = "Child 2"
+		child2.Parent = rootInstance
+
+		hydrate(knownInstances, virtualInstances, "ROOT", rootInstance)
+
+		expect(knownInstances:size()).to.equal(3)
+		expect(knownInstances.fromIds["ROOT"]).to.equal(rootInstance)
+		expect(knownInstances.fromIds["CHILD1"]).to.equal(child1)
+		expect(knownInstances.fromIds["CHILD2"]).to.equal(child2)
+	end)
+end

plugin/src/Reconciler/init.lua

@@ -0,0 +1,34 @@
+--[[
+	This module defines the meat of the Rojo plugin and how it manages tracking
+	and mutating the Roblox DOM.
+]]
+
+local applyPatch = require(script.applyPatch)
+local hydrate = require(script.hydrate)
+local diff = require(script.diff)
+
+local Reconciler = {}
+Reconciler.__index = Reconciler
+
+function Reconciler.new(instanceMap)
+	local self = {
+		-- Tracks all of the instances known by the reconciler by ID.
+		__instanceMap = instanceMap,
+	}
+
+	return setmetatable(self, Reconciler)
+end
+
+function Reconciler:applyPatch(patch)
+	return applyPatch(self.__instanceMap, patch)
+end
+
+function Reconciler:hydrate(virtualInstances, rootId, rootInstance)
+	return hydrate(self.__instanceMap, virtualInstances, rootId, rootInstance)
+end
+
+function Reconciler:diff(virtualInstances, rootId)
+	return diff(self.__instanceMap, virtualInstances, rootId)
+end
+
+return Reconciler

plugin/src/Reconciler/reify.lua

@@ -0,0 +1,152 @@
+--[[
+	"Reifies" a virtual DOM, constructing a real DOM with the same shape.
+]]
+
+local invariant = require(script.Parent.Parent.invariant)
+local PatchSet = require(script.Parent.Parent.PatchSet)
+local setProperty = require(script.Parent.setProperty)
+local decodeValue = require(script.Parent.decodeValue)
+
+local reifyInner, applyDeferredRefs
+
+local function reify(instanceMap, virtualInstances, rootId, parentInstance)
+	-- Create an empty patch that will be populated with any parts of this reify
+	-- that could not happen, like instances that couldn't be created and
+	-- properties that could not be assigned.
+	local unappliedPatch = PatchSet.newEmpty()
+
+	-- Contains a list of all of the ref properties that we'll need to assign
+	-- after all instances are created. We apply refs in a second pass, after
+	-- we create as many instances as we can, so that we ensure that referents
+	-- can be mapped to instances correctly.
+	local deferredRefs = {}
+
+	reifyInner(instanceMap, virtualInstances, rootId, parentInstance, unappliedPatch, deferredRefs)
+	applyDeferredRefs(instanceMap, deferredRefs, unappliedPatch)
+
+	return unappliedPatch
+end
+
+--[[
+	Add the given ID and all of its descendants in virtualInstances to the given
+	PatchSet, marked for addition.
+]]
+local function addAllToPatch(patchSet, virtualInstances, id)
+	local virtualInstance = virtualInstances[id]
+	patchSet.added[id] = virtualInstance
+
+	for _, childId in ipairs(virtualInstance.Children) do
+		addAllToPatch(patchSet, virtualInstances, childId)
+	end
+end
+
+--[[
+	Inner function that defines the core routine.
+]]
+function reifyInner(instanceMap, virtualInstances, id, parentInstance, unappliedPatch, deferredRefs)
+	local virtualInstance = virtualInstances[id]
+
+	if virtualInstance == nil then
+		invariant("Cannot reify an instance not present in virtualInstances\nID: {}", id)
+	end
+
+	-- Instance.new can fail if we're passing in something that can't be
+	-- created, like a service, something enabled with a feature flag, or
+	-- something that requires higher security than we have.
+	local ok, instance = pcall(Instance.new, virtualInstance.ClassName)
+
+	if not ok then
+		addAllToPatch(unappliedPatch, virtualInstances, id)
+		return
+	end
+
+	-- TODO: Can this fail? Previous versions of Rojo guarded against this, but
+	-- the reason why was uncertain.
+	instance.Name = virtualInstance.Name
+
+	-- Track all of the properties that we've failed to assign to this instance.
+	local unappliedProperties = {}
+
+	for propertyName, virtualValue in pairs(virtualInstance.Properties) do
+		-- Because refs may refer to instances that we haven't constructed yet,
+		-- we defer applying any ref properties until all instances are created.
+		if virtualValue.Type == "Ref" then
+			table.insert(deferredRefs, {
+				id = id,
+				instance = instance,
+				propertyName = propertyName,
+				virtualValue = virtualValue,
+			})
+			continue
+		end
+
+		local ok, value = decodeValue(virtualValue, instanceMap)
+		if not ok then
+			unappliedProperties[propertyName] = virtualValue
+			continue
+		end
+
+		local ok = setProperty(instance, propertyName, value)
+		if not ok then
+			unappliedProperties[propertyName] = virtualValue
+		end
+	end
+
+	-- If there were any properties that we failed to assign, push this into our
+	-- unapplied patch as an update that would need to be applied.
+	if next(unappliedProperties) ~= nil then
+		table.insert(unappliedPatch.updated, {
+			id = id,
+			changedProperties = unappliedProperties,
+		})
+	end
+
+	for _, childId in ipairs(virtualInstance.Children) do
+		reifyInner(instanceMap, virtualInstances, childId, instance, unappliedPatch, deferredRefs)
+	end
+
+	instance.Parent = parentInstance
+	instanceMap:insert(id, instance)
+end
+
+function applyDeferredRefs(instanceMap, deferredRefs, unappliedPatch)
+	local function markFailed(id, propertyName, virtualValue)
+		-- If there is already an updated entry in the unapplied patch for this
+		-- ref, use the existing one. This could match other parts of the
+		-- instance that failed to be created, or even just other refs that
+		-- failed to apply.
+		--
+		-- This is important for instances like selectable GUI objects, which
+		-- have many similar referent properties.
+		for _, existingUpdate in ipairs(unappliedPatch.updated) do
+			if existingUpdate.id == id then
+				existingUpdate.changedProperties[propertyName] = virtualValue
+				return
+			end
+		end
+
+		-- We didn't find an existing entry that matched, so push a new entry
+		-- into our unapplied patch.
+		table.insert(unappliedPatch.updated, {
+			id = id,
+			changedProperties = {
+				[propertyName] = virtualValue,
+			},
+		})
+	end
+
+	for _, entry in ipairs(deferredRefs) do
+		local targetInstance = instanceMap.fromIds[entry.virtualValue.Value]
+		if targetInstance == nil then
+			markFailed(entry.id, entry.propertyName, entry.virtualValue)
+			continue
+		end
+
+		local ok = setProperty(entry.instance, entry.propertyName, targetInstance)
+		if not ok then
+			markFailed(entry.id, entry.propertyName, entry.virtualValue)
+		end
+	end
+end
+
+return reify

plugin/src/Reconciler/reify.spec.lua

@@ -0,0 +1,352 @@
+return function()
+	local reify = require(script.Parent.reify)
+
+	local PatchSet = require(script.Parent.Parent.PatchSet)
+	local InstanceMap = require(script.Parent.Parent.InstanceMap)
+	local Error = require(script.Parent.Error)
+
+	local function isEmpty(table)
+		return next(table) == nil, "Table was not empty"
+	end
+
+	local function size(dict)
+		local len = 0
+
+		for _ in pairs(dict) do
+			len = len + 1
+		end
+
+		return len
+	end
+
+	it("should throw when given a bogus ID", function()
+		expect(function()
+			reify(InstanceMap.new(), {}, "Hi, mom!", game)
+		end).to.throw()
+	end)
+
+	it("should return an error when given bogus class names", function()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Balogna",
+				Name = "Food",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local instanceMap = InstanceMap.new()
+		local unappliedPatch = reify(instanceMap, virtualInstances, "ROOT", nil)
+
+		assert(instanceMap:size() == 0, "expected instanceMap to be empty")
+
+		expect(size(unappliedPatch.added)).to.equal(1)
+		expect(unappliedPatch.added["ROOT"]).to.equal(virtualInstances["ROOT"])
+
+		assert(isEmpty(unappliedPatch.removed), "expected no removes")
+		assert(isEmpty(unappliedPatch.updated), "expected no updates")
+	end)
+
+	it("should assign name and properties", function()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "StringValue",
+				Name = "Spaghetti",
+				Properties = {
+					Value = {
+						Type = "String",
+						Value = "Hello, world!",
+					},
+				},
+				Children = {},
+			},
+		}
+
+		local instanceMap = InstanceMap.new()
+		local unappliedPatch = reify(instanceMap, virtualInstances, "ROOT")
+
+		assert(PatchSet.isEmpty(unappliedPatch), "expected remaining patch to be empty")
+
+		local instance = instanceMap.fromIds["ROOT"]
+		expect(instance.ClassName).to.equal("StringValue")
+		expect(instance.Name).to.equal("Spaghetti")
+		expect(instance.Value).to.equal("Hello, world!")
+
+		expect(instanceMap:size()).to.equal(1)
+	end)
+
+	it("should construct children", function()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Parent",
+				Properties = {},
+				Children = {"CHILD"},
+			},
+
+			CHILD = {
+				ClassName = "Folder",
+				Name = "Child",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local instanceMap = InstanceMap.new()
+		local unappliedPatch = reify(instanceMap, virtualInstances, "ROOT")
+
+		assert(PatchSet.isEmpty(unappliedPatch), "expected remaining patch to be empty")
+
+		local instance = instanceMap.fromIds["ROOT"]
+		expect(instance.ClassName).to.equal("Folder")
+		expect(instance.Name).to.equal("Parent")
+
+		local child = instance.Child
+		expect(child.ClassName).to.equal("Folder")
+
+		expect(instanceMap:size()).to.equal(2)
+	end)
+
+	it("should still construct parents if children fail", function()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Parent",
+				Properties = {},
+				Children = {"CHILD"},
+			},
+
+			CHILD = {
+				ClassName = "this ain't an Instance",
+				Name = "Child",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local instanceMap = InstanceMap.new()
+		local unappliedPatch = reify(instanceMap, virtualInstances, "ROOT")
+
+		expect(size(unappliedPatch.added)).to.equal(1)
+		expect(unappliedPatch.added["CHILD"]).to.equal(virtualInstances["CHILD"])
+		assert(isEmpty(unappliedPatch.updated), "expected no updates")
+		assert(isEmpty(unappliedPatch.removed), "expected no removes")
+
+		local instance = instanceMap.fromIds["ROOT"]
+		expect(instance.ClassName).to.equal("Folder")
+		expect(instance.Name).to.equal("Parent")
+
+		expect(#instance:GetChildren()).to.equal(0)
+		expect(instanceMap:size()).to.equal(1)
+	end)
+
+	it("should fail gracefully when setting erroneous properties", function()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "StringValue",
+				Name = "Root",
+				Properties = {
+					Value = {
+						Type = "Vector3",
+						Value = {1, 2, 3},
+					},
+				},
+				Children = {},
+			},
+		}
+
+		local instanceMap = InstanceMap.new()
+		local unappliedPatch = reify(instanceMap, virtualInstances, "ROOT")
+
+		local instance = instanceMap.fromIds["ROOT"]
+		expect(instance.ClassName).to.equal("StringValue")
+		expect(instance.Name).to.equal("Root")
+
+		assert(isEmpty(unappliedPatch.added), "expected no additions")
+		expect(#unappliedPatch.updated).to.equal(1)
+		assert(isEmpty(unappliedPatch.removed), "expected no removes")
+
+		local update = unappliedPatch.updated[1]
+		expect(update.id).to.equal("ROOT")
+		expect(size(update.changedProperties)).to.equal(1)
+
+		local property = update.changedProperties["Value"]
+		expect(property).to.equal(virtualInstances["ROOT"].Properties.Value)
+	end)
+
+	-- This is the simplest ref case: ensure that setting a ref property that
+	-- points to an instance that was previously created as part of the same
+	-- reify operation works.
+	it("should apply properties containing refs to ancestors", function()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Root",
+				Properties = {},
+				Children = {"CHILD"},
+			},
+
+			CHILD = {
+				ClassName = "ObjectValue",
+				Name = "Child",
+				Properties = {
+					Value = {
+						Type = "Ref",
+						Value = "ROOT",
+					},
+				},
+				Children = {},
+			},
+		}
+
+		local instanceMap = InstanceMap.new()
+		local unappliedPatch = reify(instanceMap, virtualInstances, "ROOT")
+
+		assert(PatchSet.isEmpty(unappliedPatch), "expected remaining patch to be empty")
+
+		local root = instanceMap.fromIds["ROOT"]
+		local child = instanceMap.fromIds["CHILD"]
+		expect(child.Value).to.equal(root)
+	end)
+
+	-- This is another simple case: apply a ref property that points to an
+	-- existing instance. In this test, that instance was created before the
+	-- reify operation started and is present in instanceMap.
+	it("should apply properties containing refs to previously-existing instances", function()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "ObjectValue",
+				Name = "Root",
+				Properties = {
+					Value = {
+						Type = "Ref",
+						Value = "EXISTING",
+					},
+				},
+				Children = {},
+			},
+		}
+
+		local instanceMap = InstanceMap.new()
+
+		local existing = Instance.new("Folder")
+		existing.Name = "Existing"
+		instanceMap:insert("EXISTING", existing)
+
+		local unappliedPatch = reify(instanceMap, virtualInstances, "ROOT")
+
+		assert(PatchSet.isEmpty(unappliedPatch), "expected remaining patch to be empty")
+
+		local root = instanceMap.fromIds["ROOT"]
+		expect(root.Value).to.equal(existing)
+	end)
+
+	-- This is a tricky ref case: CHILD_A points to CHILD_B, but is constructed
+	-- first. Deferred ref application is required to implement this case
+	-- correctly.
+	it("should apply properties containing refs to later siblings correctly", function()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "Folder",
+				Name = "Root",
+				Properties = {},
+				Children = {"CHILD_A", "CHILD_B"},
+			},
+
+			CHILD_A = {
+				ClassName = "ObjectValue",
+				Name = "Child A",
+				Properties = {
+					Value = {
+						Type = "Ref",
+						Value = "Child B",
+					},
+				},
+				Children = {},
+			},
+
+			CHILD_B = {
+				ClassName = "Folder",
+				Name = "Child B",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local instanceMap = InstanceMap.new()
+		local unappliedPatch = reify(instanceMap, virtualInstances, "ROOT")
+
+		assert(PatchSet.isEmpty(unappliedPatch), "expected remaining patch to be empty")
+
+		local childA = instanceMap.fromIds["CHILD_A"]
+		local childB = instanceMap.fromIds["CHILD_B"]
+		expect(childA.Value).to.equal(childB)
+	end)
+
+	-- This is the classic case that calls for deferred ref application. In this
+	-- test, the root instance has a ref property that refers to its child. The
+	-- root is definitely constructed first.
+	--
+	-- This is distinct from the sibling case in that the child will be
+	-- constructed as part of a recursive call before the parent has totally
+	-- finished. Given deferred refs, this should not fail, but it is a good
+	-- case to test.
+	it("should apply properties containing refs to later siblings correctly", function()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "ObjectValue",
+				Name = "Root",
+				Properties = {
+					Value = {
+						Type = "Ref",
+						Value = "CHILD",
+					},
+				},
+				Children = {"CHILD"},
+			},
+
+			CHILD = {
+				ClassName = "Folder",
+				Name = "Child",
+				Properties = {},
+				Children = {},
+			},
+		}
+
+		local instanceMap = InstanceMap.new()
+		local unappliedPatch = reify(instanceMap, virtualInstances, "ROOT")
+
+		assert(PatchSet.isEmpty(unappliedPatch), "expected remaining patch to be empty")
+
+		local root = instanceMap.fromIds["ROOT"]
+		local child = instanceMap.fromIds["CHILD"]
+		expect(root.Value).to.equal(child)
+	end)
+
+	it("should return a partial patch when applying invalid refs", function()
+		local virtualInstances = {
+			ROOT = {
+				ClassName = "ObjectValue",
+				Name = "Root",
+				Properties = {
+					Value = {
+						Type = "Ref",
+						Value = "SORRY",
+					},
+				},
+				Children = {},
+			},
+		}
+
+		local instanceMap = InstanceMap.new()
+		local unappliedPatch = reify(instanceMap, virtualInstances, "ROOT")
+
+		assert(not PatchSet.hasRemoves(unappliedPatch), "expected no removes")
+		assert(not PatchSet.hasAdditions(unappliedPatch), "expected no additions")
+		expect(#unappliedPatch.updated).to.equal(1)
+
+		local update = unappliedPatch.updated[1]
+		expect(update.id).to.equal("ROOT")
+		expect(update.changedProperties.Value).to.equal(virtualInstances["ROOT"].Properties.Value)
+	end)
+end

plugin/src/Reconciler/setProperty.lua

@@ -0,0 +1,48 @@
+--[[
+	Attempts to set a property on the given instance.
+]]
+
+local RbxDom = require(script.Parent.Parent.Parent.RbxDom)
+local Log = require(script.Parent.Parent.Parent.Log)
+local Error = require(script.Parent.Error)
+
+local function setProperty(instance, propertyName, value)
+	local descriptor = RbxDom.findCanonicalPropertyDescriptor(instance.ClassName, propertyName)
+
+	-- We can skip unknown properties; they're not likely reflected to Lua.
+	--
+	-- A good example of a property like this is `Model.ModelInPrimary`, which
+	-- is serialized but not reflected to Lua.
+	if descriptor == nil then
+		Log.trace("Skipping unknown property {}.{}", instance.ClassName, propertyName)
+
+		return true
+	end
+
+	if descriptor.scriptability == "None" or descriptor.scriptability == "Read" then
+		return false, Error.new(Error.UnwritableProperty, {
+			className = instance.ClassName,
+			propertyName = propertyName,
+		})
+	end
+
+	local ok, err = descriptor:write(instance, value)
+
+	if not ok then
+		if err.kind == RbxDom.Error.Kind.Roblox and err.extra:find("lacking permission") then
+			return false, Error.new(Error.LackingPropertyPermissions, {
+				className = instance.ClassName,
+				propertyName = propertyName,
+			})
+		end
+
+		return false, Error.new(Error.OtherPropertyError, {
+			className = instance.ClassName,
+			propertyName = propertyName,
+		})
+	end
+
+	return true
+end
+
+return setProperty

plugin/src/ServeSession.lua

@@ -1,9 +1,11 @@
+local StudioService = game:GetService("StudioService")
+
 local Log = require(script.Parent.Parent.Log)
 local Fmt = require(script.Parent.Parent.Fmt)
 local t = require(script.Parent.Parent.t)
 
-local DevSettings = require(script.Parent.DevSettings)
 local InstanceMap = require(script.Parent.InstanceMap)
+local PatchSet = require(script.Parent.PatchSet)
 local Reconciler = require(script.Parent.Reconciler)
 local strict = require(script.Parent.strict)
 
@@ -43,6 +45,8 @@ ServeSession.Status = Status
 
 local validateServeOptions = t.strictInterface({
 	apiContext = t.table,
+	openScriptsExternally = t.boolean,
+	twoWaySync = t.boolean,
 })
 
 function ServeSession.new(options)
@@ -57,12 +61,28 @@ function ServeSession.new(options)
 	local instanceMap = InstanceMap.new(onInstanceChanged)
 	local reconciler = Reconciler.new(instanceMap)
 
+	local connections = {}
+
+	local connection = StudioService
+		:GetPropertyChangedSignal("ActiveScript")
+		:Connect(function()
+			local activeScript = StudioService.ActiveScript
+
+			if activeScript ~= nil then
+				self:__onActiveScriptChanged(activeScript)
+			end
+		end)
+	table.insert(connections, connection)
+
 	self = {
 		__status = Status.NotStarted,
 		__apiContext = options.apiContext,
+		__openScriptsExternally = options.openScriptsExternally,
+		__twoWaySync = options.twoWaySync,
 		__reconciler = reconciler,
 		__instanceMap = instanceMap,
 		__statusChangedCallback = nil,
+		__connections = connections,
 	}
 
 	setmetatable(self, ServeSession)
@@ -108,8 +128,39 @@ function ServeSession:stop()
 	self:__stopInternal()
 end
 
+function ServeSession:__onActiveScriptChanged(activeScript)
+	if not self.__openScriptsExternally then
+		Log.trace("Not opening script {} because feature not enabled.", activeScript)
+
+		return
+	end
+
+	if self.__status ~= Status.Connected then
+		Log.trace("Not opening script {} because session is not connected.", activeScript)
+
+		return
+	end
+
+	local scriptId = self.__instanceMap.fromInstances[activeScript]
+	if scriptId == nil then
+		Log.trace("Not opening script {} because it is not known by Rojo.", activeScript)
+
+		return
+	end
+
+	Log.debug("Trying to open script {} externally...", activeScript)
+
+	-- Force-close the script inside Studio
+	local existingParent = activeScript.Parent
+	activeScript.Parent = nil
+	activeScript.Parent = existingParent
+
+	-- Notify the Rojo server to open this script
+	self.__apiContext:open(scriptId)
+end
+
 function ServeSession:__onInstanceChanged(instance, propertyName)
-	if not DevSettings:twoWaySyncEnabled() then
+	if not self.__twoWaySync then
 		return
 	end
 
@@ -164,22 +215,36 @@ function ServeSession:__initialSync(rootInstanceId)
 			-- the tree defined in this response.
 			self.__apiContext:setMessageCursor(readResponseBody.messageCursor)
 
-			Log.trace("Computing changes that plugin needs to make to catch up to server...")
+			-- For any instances that line up with the Rojo server's view, start
+			-- tracking them in the reconciler.
+			Log.trace("Matching existing Roblox instances to Rojo IDs")
+			self.__reconciler:hydrate(readResponseBody.instances, rootInstanceId, game)
 
 			-- Calculate the initial patch to apply to the DataModel to catch us
 			-- up to what Rojo thinks the place should look like.
-			local hydratePatch = self.__reconciler:hydrate(
+			Log.trace("Computing changes that plugin needs to make to catch up to server...")
+			local success, catchUpPatch = self.__reconciler:diff(
 				readResponseBody.instances,
 				rootInstanceId,
 				game
 			)
 
-			Log.trace("Computed hydration patch: {:#?}", debugPatch(hydratePatch))
+			if not success then
+				Log.error("Could not compute a diff to catch up to the Rojo server: {:#?}", catchUpPatch)
+			end
+
+			Log.trace("Computed hydration patch: {:#?}", debugPatch(catchUpPatch))
 
 			-- TODO: Prompt user to notify them of this patch, since it's
-			-- effectively a conflict between the Rojo server and the client.
+			-- effectively a conflict between the Rojo server and the client. In
+			-- the future, we'll ask which changes the user wants to keep.
 
-			self.__reconciler:applyPatch(hydratePatch)
+			local unappliedPatch = self.__reconciler:applyPatch(catchUpPatch)
+
+			if not PatchSet.isEmpty(unappliedPatch) then
+				Log.warn("Could not apply all changes requested by the Rojo server:\n{}",
+					PatchSet.humanSummary(self.__instanceMap, unappliedPatch))
+			end
 		end)
 end
 
@@ -187,7 +252,12 @@ function ServeSession:__mainSyncLoop()
 	return self.__apiContext:retrieveMessages()
 		:andThen(function(messages)
 			for _, message in ipairs(messages) do
-				self.__reconciler:applyPatch(message)
+				local unappliedPatch = self.__reconciler:applyPatch(message)
+
+				if not PatchSet.isEmpty(unappliedPatch) then
+					Log.warn("Could not apply all changes requested by the Rojo server:\n{}",
+						PatchSet.humanSummary(self.__instanceMap, unappliedPatch))
+				end
 			end
 
 			if self.__status ~= Status.Disconnected then
@@ -200,6 +270,11 @@ function ServeSession:__stopInternal(err)
 	self:__setStatus(Status.Disconnected, err)
 	self.__apiContext:disconnect()
 	self.__instanceMap:stop()
+
+	for _, connection in ipairs(self.__connections) do
+		connection:Disconnect()
+	end
+	self.__connections = {}
 end
 
 function ServeSession:__setStatus(status, detail)

plugin/src/createSignal.lua

@@ -0,0 +1,53 @@
+--[[
+	Create a new signal that can be connected to, disconnected from, and fired.
+
+	Usage:
+
+		local signal = createSignal()
+		local disconnect = signal:connect(function(...)
+			print("fired:", ...)
+		end)
+
+		signal:fire("a", "b", "c")
+		disconnect()
+
+	Avoids mutating listeners list directly to prevent iterator invalidation if
+	a listener is disconnected while the signal is firing.
+]]
+local function createSignal()
+	local listeners = {}
+
+	local function connect(newListener)
+		local nextListeners = {}
+		for listener in pairs(listeners) do
+			nextListeners[listener] = true
+		end
+
+		nextListeners[newListener] = true
+		listeners = nextListeners
+
+		return function()
+			local nextListeners = {}
+			for listener in pairs(listeners) do
+				if listener ~= newListener then
+					nextListeners[listener] = true
+				end
+			end
+
+			listeners = nextListeners
+		end
+	end
+
+	local function fire(...)
+		for listener in pairs(listeners) do
+			listener(...)
+		end
+	end
+
+	return {
+		connect = connect,
+		fire = fire,
+	}
+end
+
+return createSignal

plugin/src/init.server.lua

@@ -14,9 +14,17 @@ local Roact = require(script.Parent.Roact)
 
 local Config = require(script.Config)
 local App = require(script.Components.App)
+local Theme = require(script.Components.Theme)
+local PluginSettings = require(script.Components.PluginSettings)
 
-local app = Roact.createElement(App, {
-	plugin = plugin,
+local app = Roact.createElement(Theme.StudioProvider, nil, {
+	Roact.createElement(PluginSettings.StudioProvider, {
+		plugin = plugin,
+	}, {
+		RojoUI = Roact.createElement(App, {
+			plugin = plugin,
+		}),
+	})
 })
 
 local tree = Roact.mount(app, nil, "Rojo UI")

plugin/src/setCanonicalProperty.lua

@@ -1,37 +0,0 @@
-local RbxDom = require(script.Parent.Parent.RbxDom)
-
---[[
-	Attempts to set a property on the given instance.
-]]
-local function setCanonicalProperty(instance, propertyName, value)
-	local descriptor = RbxDom.findCanonicalPropertyDescriptor(instance.ClassName, propertyName)
-
-	-- We can skip unknown properties; they're not likely reflected to Lua.
-	--
-	-- A good example of a property like this is `Model.ModelInPrimary`, which
-	-- is serialized but not reflected to Lua.
-	if descriptor == nil then
-		return false, "unknown property"
-	end
-
-	if descriptor.scriptability == "None" or descriptor.scriptability == "Read" then
-		return false, "unwritable property"
-	end
-
-	local success, err = descriptor:write(instance, value)
-
-	if not success then
-		-- If we don't have permission to write a property, we just silently
-		-- ignore it.
-		if err.kind == RbxDom.Error.Kind.Roblox and err.extra:find("lacking permission") then
-			return false, "permission error"
-		end
-
-		local message = ("Invalid property %s.%s: %s"):format(descriptor.className, descriptor.name, tostring(err))
-		error(message, 2)
-	end
-
-	return true
-end
-
-return setCanonicalProperty

plugin/test

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+rojo build test-place.project.json -o TestPlace.rbxlx
+run-in-roblox --script run-tests.server.lua --place TestPlace.rbxlx

plugin/test-place.project.json

@@ -0,0 +1,28 @@
+{
+  "name": "Rojo Test Place",
+  "tree": {
+    "$className": "DataModel",
+
+    "ReplicatedStorage": {
+      "Rojo": {
+        "$path": "default.project.json"
+      },
+
+      "TestEZ": {
+        "$path": "modules/testez/lib"
+      }
+    },
+
+    "ServerScriptService": {
+      "RunTests": {
+        "$path": "run-tests.server.lua"
+      }
+    },
+
+    "Players": {
+      "$properties": {
+        "CharacterAutoLoads": false
+      }
+    }
+  }
+}

plugin/testez.project.json

@@ -1,6 +0,0 @@
-{
-  "name": "TestEZ",
-  "tree": {
-    "$path": "modules/testez/lib"
-  }
-}

rojo-test/Cargo.toml

@@ -1,29 +0,0 @@
-[package]
-name = "rojo-test"
-version = "0.1.0"
-authors = ["Lucien Greathouse <me@lpghatguy.com>"]
-edition = "2018"
-publish = false
-
-[features]
-default = []
-
-unstable_glob_ignore_paths = []
-
-[dependencies]
-env_logger = "0.7.1"
-insta = { version = "0.13.1", features = ["redactions"] }
-log = "0.4.8"
-paste = "0.1.5"
-rbx_dom_weak = "1.9.0"
-reqwest = "0.9.20"
-serde = "1.0.99"
-serde_json = "1.0.40"
-serde_yaml = "0.8.9"
-tempfile = "3.1.0"
-walkdir = "2.2.9"
-
-rojo-insta-ext = { path = "../rojo-insta-ext" }
-
-# We execute Rojo via std::process::Command, so depend on it so it's built!
-rojo = { path = ".." }

rojo-test/README.md

@@ -1,8 +0,0 @@
-# rojo-test
-This project does end-to-end testing of Rojo by executing it and checking what side-effects it has.
-
-rojo-test is meant to be run as a test with:
-
-```bash
-cargo test
-```

rojo-test/build-test-snapshots/end_to_end__tests__build__client_in_folder.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__client_init.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__csv_bug_145.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__csv_bug_147.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__csv_in_folder.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__deep_nesting.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__gitkeep.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__ignore_glob_inner.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__ignore_glob_nested.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__ignore_glob_spec.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__infer_service_name.snap

@@ -0,0 +1,28 @@
+---
+source: tests/tests/build.rs
+expression: contents
+---
+<roblox version="4">
+  <Item class="DataModel" referent="0">
+    <Properties>
+      <string name="Name">infer-service-name</string>
+    </Properties>
+    <Item class="HttpService" referent="1">
+      <Properties>
+        <string name="Name">HttpService</string>
+        <bool name="HttpEnabled">true</bool>
+      </Properties>
+    </Item>
+    <Item class="ReplicatedStorage" referent="2">
+      <Properties>
+        <string name="Name">ReplicatedStorage</string>
+      </Properties>
+      <Item class="ModuleScript" referent="3">
+        <Properties>
+          <string name="Name">Main</string>
+          <string name="Source">-- hello, from main</string>
+        </Properties>
+      </Item>
+    </Item>
+  </Item>
+</roblox>

rojo-test/build-test-snapshots/end_to_end__tests__build__infer_starter_player.snap

@@ -0,0 +1,26 @@
+---
+source: tests/tests/build.rs
+expression: contents
+---
+<roblox version="4">
+  <Item class="DataModel" referent="0">
+    <Properties>
+      <string name="Name">infer-service-name</string>
+    </Properties>
+    <Item class="StarterPlayer" referent="1">
+      <Properties>
+        <string name="Name">StarterPlayer</string>
+      </Properties>
+      <Item class="StarterCharacterScripts" referent="2">
+        <Properties>
+          <string name="Name">StarterCharacterScripts</string>
+        </Properties>
+      </Item>
+      <Item class="StarterPlayerScripts" referent="3">
+        <Properties>
+          <string name="Name">StarterPlayerScripts</string>
+        </Properties>
+      </Item>
+    </Item>
+  </Item>
+</roblox>

rojo-test/build-test-snapshots/end_to_end__tests__build__init_meta_class_name.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__init_meta_properties.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__init_with_children.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__json_as_lua.snap

@@ -0,0 +1,23 @@
+---
+source: tests/tests/build.rs
+expression: contents
+---
+<roblox version="4">
+  <Item class="ModuleScript" referent="0">
+    <Properties>
+      <string name="Name">json_as_lua</string>
+      <string name="Source">return {
+	["1invalidident"] = "nice",
+	array = {1, 2, 3},
+	["false"] = false,
+	float = 1234.5452,
+	int = 1234,
+	null = nil,
+	object = {
+		hello = "world",
+	},
+	["true"] = true,
+}</string>
+    </Properties>
+  </Item>
+</roblox>

rojo-test/build-test-snapshots/end_to_end__tests__build__json_model_in_folder.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__json_model_legacy_name.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__module_in_folder.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__module_init.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__rbxm_in_folder.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__rbxmx_in_folder.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__rbxmx_ref.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">

rojo-test/build-test-snapshots/end_to_end__tests__build__script_meta_disabled.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/build_test.rs
+source: tests/tests/build.rs
 expression: contents
 ---
 <roblox version="4">