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

@@ -1,9 +1,13 @@
 name: CI
 
 on:
-  pull_request:
   push:
-    branches: ["*"]
+    branches:
+    - master
+
+  pull_request:
+    branches:
+    - master
 
 jobs:
   build:
@@ -12,7 +16,7 @@ jobs:
 
     strategy:
       matrix:
-        rust_version: [stable, "1.40.0"]
+        rust_version: [stable, "1.43.1"]
 
     steps:
     - uses: actions/checkout@v1
@@ -32,10 +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'

.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

.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

@@ -2,6 +2,17 @@
 
 ## 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.
 
@@ -122,7 +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.
@@ -319,4 +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.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rojo"
-version = "6.0.0-rc.1"
+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"
@@ -23,15 +23,11 @@ panic = "abort"
 [features]
 default = []
 
-# Turn on support for specifying glob ignore path rules in the project format.
-unstable_glob_ignore_paths = []
-
 # Enable this feature to live-reload assets from the web UI.
 dev_live_assets = []
 
 [workspace]
 members = [
-    "rojo-test",
     "rojo-insta-ext",
     "clibrojo",
     "memofs",
@@ -39,7 +35,6 @@ members = [
 
 default-members = [
     ".",
-    "rojo-test",
     "rojo-insta-ext",
     "memofs",
 ]
@@ -97,7 +92,7 @@ uuid = { version = "0.8.1", features = ["v4", "serde"] }
 winreg = "0.6.2"
 
 [build-dependencies]
-memofs = { version = "0.1.0", path = "memofs" }
+memofs = { version = "0.1.3", path = "memofs" }
 
 anyhow = "1.0.27"
 bincode = "1.2.1"

README.md

@@ -48,7 +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/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,
     };
 

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 +1,10 @@
 # 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.

memofs/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "memofs"
 description = "Virtual filesystem with configurable backends."
-version = "0.1.2"
+version = "0.1.3"
 authors = ["Lucien Greathouse <me@lpghatguy.com>"]
 edition = "2018"
 readme = "README.md"

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.
     ///

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/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/README.md

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

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

@@ -5,7 +5,7 @@ local isDevBuild = script.Parent.Parent:FindFirstChild("ROJO_DEV_BUILD") ~= nil
 return strict("Config", {
 	isDevBuild = isDevBuild,
 	codename = "Epiphany",
-	version = {6, 0, 0, "-rc.1"},
+	version = {6, 0, 0, "-rc.2"},
 	expectedServerVersionString = "6.0 or newer",
 	protocolVersion = 3,
 	defaultHost = "localhost",

plugin/src/InstanceMap.lua

@@ -33,6 +33,16 @@ function InstanceMap.new(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.
 ]]
@@ -69,6 +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)
@@ -81,8 +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
 
@@ -93,8 +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
 
@@ -102,10 +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)
@@ -113,21 +126,11 @@ 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()
-	else
-		Log.warn("Attempted to destroy nonexistant ID {}", id)
 	end
 end
 

plugin/src/PatchSet.lua

@@ -16,10 +16,169 @@ PatchSet.validate = t.interface({
 })
 
 --[[
-	Invert the given PatchSet using the given instance map.
+	Create a new, empty PatchSet.
 ]]
-function PatchSet.invert(patchSet, instanceMap)
-	error("not yet implemented", 2)
+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

@@ -1,389 +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 Types = require(script.Parent.Types)
-local invariant = require(script.Parent.invariant)
-local getCanonicalProperty = require(script.Parent.getCanonicalProperty)
-local setCanonicalProperty = require(script.Parent.setCanonicalProperty)
-local PatchSet = require(script.Parent.PatchSet)
-
---[[
-	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(
-	PatchSet.validate
-))
-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,
-	PatchSet.validate
-))
-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 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

@@ -5,6 +5,7 @@ local Fmt = require(script.Parent.Parent.Fmt)
 local t = require(script.Parent.Parent.t)
 
 local InstanceMap = require(script.Parent.InstanceMap)
+local PatchSet = require(script.Parent.PatchSet)
 local Reconciler = require(script.Parent.Reconciler)
 local strict = require(script.Parent.strict)
 
@@ -214,22 +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
 
@@ -237,7 +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

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

@@ -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_starter_player.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_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

@@ -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_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">

rojo-test/build-test-snapshots/end_to_end__tests__build__server_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__server_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__txt.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__txt_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/rojo_test__build_test__plain.txt.snap

@@ -1,12 +0,0 @@
----
-source: rojo-test/src/build_test.rs
-expression: contents
----
-<roblox version="4">
-  <Item class="StringValue" referent="0">
-    <Properties>
-      <string name="Name">plain</string>
-      <string name="Value">This is a bare text file with no project.</string>
-    </Properties>
-  </Item>
-</roblox>

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

@@ -1,11 +0,0 @@
----
-source: rojo-test/src/build_test.rs
-expression: contents
----
-<roblox version="4">
-  <Item class="Folder" referent="0">
-    <Properties>
-      <string name="Name">plain_gitkeep</string>
-    </Properties>
-  </Item>
-</roblox>

rojo-test/serve-test-snapshots/end_to_end__tests__serve__add_folder_all-2.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__add_folder_all.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__add_folder_info.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: redactions.redacted_yaml(info)
 ---
 expectedPlaceIds: ~

rojo-test/serve-test-snapshots/end_to_end__tests__serve__add_folder_subscribe.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "subscribe_response.intern_and_redact(&mut redactions, ())"
 ---
 messageCursor: 1

rojo-test/serve-test-snapshots/end_to_end__tests__serve__edit_init_all-2.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__edit_init_all.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__edit_init_info.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: redactions.redacted_yaml(info)
 ---
 expectedPlaceIds: ~

rojo-test/serve-test-snapshots/end_to_end__tests__serve__edit_init_subscribe.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "subscribe_response.intern_and_redact(&mut redactions, ())"
 ---
 messageCursor: 1

rojo-test/serve-test-snapshots/end_to_end__tests__serve__empty_all.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__empty_info.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: redactions.redacted_yaml(info)
 ---
 expectedPlaceIds: ~

rojo-test/serve-test-snapshots/end_to_end__tests__serve__move_folder_of_stuff_all-2.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__move_folder_of_stuff_all.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__move_folder_of_stuff_info.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: redactions.redacted_yaml(info)
 ---
 expectedPlaceIds: ~

rojo-test/serve-test-snapshots/end_to_end__tests__serve__move_folder_of_stuff_subscribe.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "subscribe_response.intern_and_redact(&mut redactions, ())"
 ---
 messageCursor: 1

rojo-test/serve-test-snapshots/end_to_end__tests__serve__remove_file_all-2.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__remove_file_all.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__remove_file_info.snap

@@ -0,0 +1,9 @@
+---
+source: tests/tests/serve.rs
+expression: redactions.redacted_yaml(info)
+---
+expectedPlaceIds: ~
+protocolVersion: 3
+rootInstanceId: id-2
+serverVersion: "[server-version]"
+sessionId: id-1

rojo-test/serve-test-snapshots/end_to_end__tests__serve__remove_file_subscribe.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "subscribe_response.intern_and_redact(&mut redactions, ())"
 ---
 messageCursor: 1

rojo-test/serve-test-snapshots/end_to_end__tests__serve__scripts_all-2.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__scripts_all.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "read_response.intern_and_redact(&mut redactions, root_id)"
 ---
 instances:

rojo-test/serve-test-snapshots/end_to_end__tests__serve__scripts_info.snap

@@ -0,0 +1,9 @@
+---
+source: tests/tests/serve.rs
+expression: redactions.redacted_yaml(info)
+---
+expectedPlaceIds: ~
+protocolVersion: 3
+rootInstanceId: id-2
+serverVersion: "[server-version]"
+sessionId: id-1

rojo-test/serve-test-snapshots/end_to_end__tests__serve__scripts_subscribe.snap

@@ -1,5 +1,5 @@
 ---
-source: rojo-test/src/serve_test.rs
+source: tests/tests/serve.rs
 expression: "subscribe_response.intern_and_redact(&mut redactions, ())"
 ---
 messageCursor: 1

rojo-test/serve-test-snapshots/rojo_test__serve_test__just_txt_all.snap

@@ -1,19 +0,0 @@
----
-source: rojo-test/src/serve_test.rs
-expression: "read_response.intern_and_redact(&mut redactions, root_id)"
----
-instances:
-  id-2:
-    Children: []
-    ClassName: StringValue
-    Id: id-2
-    Metadata:
-      ignoreUnknownInstances: false
-    Name: just_txt
-    Parent: ~
-    Properties:
-      Value:
-        Type: String
-        Value: "Hello, world!"
-messageCursor: 0
-sessionId: id-1

rojo-test/serve-test-snapshots/rojo_test__serve_test__move_folder_of_stuff_info.snap

@@ -1,9 +0,0 @@
----
-source: rojo-test/src/serve_test.rs
-expression: redactions.redacted_yaml(info)
----
-expectedPlaceIds: ~
-protocolVersion: 3
-rootInstanceId: id-2
-serverVersion: "[server-version]"
-sessionId: id-1

rojo-test/serve-test-snapshots/rojo_test__serve_test__remove_file_info.snap

@@ -1,9 +0,0 @@
----
-source: rojo-test/src/serve_test.rs
-expression: redactions.redacted_yaml(info)
----
-expectedPlaceIds: ~
-protocolVersion: 3
-rootInstanceId: id-2
-serverVersion: "[server-version]"
-sessionId: id-1