feature init csv (#594)

* init csv feature + test

* fmt fixes

src/snapshot_middleware/csv.rs

@@ -7,7 +7,11 @@ use serde::Serialize;
 
 use crate::snapshot::{InstanceContext, InstanceMetadata, InstanceSnapshot};
 
-use super::{meta_file::AdjacentMetadata, util::PathExt};
+use super::{
+    dir::{dir_meta, snapshot_dir_no_meta},
+    meta_file::AdjacentMetadata,
+    util::PathExt,
+};
 
 pub fn snapshot_csv(
     _context: &InstanceContext,
@@ -46,6 +50,43 @@ pub fn snapshot_csv(
     Ok(Some(snapshot))
 }
 
+/// Attempts to snapshot an 'init' csv contained inside of a folder with
+/// the given name.
+///
+/// csv named `init.csv`
+/// their parents, which acts similarly to `__init__.py` from the Python world.
+pub fn snapshot_csv_init(
+    context: &InstanceContext,
+    vfs: &Vfs,
+    init_path: &Path,
+) -> anyhow::Result<Option<InstanceSnapshot>> {
+    let folder_path = init_path.parent().unwrap();
+    let dir_snapshot = snapshot_dir_no_meta(context, vfs, folder_path)?.unwrap();
+
+    if dir_snapshot.class_name != "Folder" {
+        anyhow::bail!(
+            "init.csv can only be used if the instance produced by \
+             the containing directory would be a Folder.\n\
+             \n\
+             The directory {} turned into an instance of class {}.",
+            folder_path.display(),
+            dir_snapshot.class_name
+        );
+    }
+
+    let mut init_snapshot = snapshot_csv(context, vfs, init_path)?.unwrap();
+
+    init_snapshot.name = dir_snapshot.name;
+    init_snapshot.children = dir_snapshot.children;
+    init_snapshot.metadata = dir_snapshot.metadata;
+
+    if let Some(mut meta) = dir_meta(vfs, folder_path)? {
+        meta.apply_all(&mut init_snapshot)?;
+    }
+
+    Ok(Some(init_snapshot))
+}
+
 /// Struct that holds any valid row from a Roblox CSV translation table.
 ///
 /// We manually deserialize into this table from CSV, but let serde_json handle

src/snapshot_middleware/mod.rs

@@ -24,7 +24,7 @@ use memofs::{IoResultExt, Vfs};
 use crate::snapshot::{InstanceContext, InstanceSnapshot};
 
 use self::{
-    csv::snapshot_csv,
+    csv::{snapshot_csv, snapshot_csv_init},
     dir::snapshot_dir,
     json::snapshot_json,
     json_model::snapshot_json_model,
@@ -87,12 +87,19 @@ pub fn snapshot_from_vfs(
             return snapshot_lua_init(context, vfs, &init_path);
         }
 
+        let init_path = path.join("init.csv");
+        if vfs.metadata(&init_path).with_not_found()?.is_some() {
+            return snapshot_csv_init(context, vfs, &init_path);
+        }
+
         snapshot_dir(context, vfs, path)
     } else {
         let script_name = path
             .file_name_trim_end(".lua")
             .or_else(|_| path.file_name_trim_end(".luau"));
 
+        let csv_name = path.file_name_trim_end(".csv");
+
         if let Ok(name) = script_name {
             match name {
                 // init scripts are handled elsewhere and should not turn into
@@ -110,8 +117,14 @@ pub fn snapshot_from_vfs(
             return Ok(None);
         } else if path.file_name_ends_with(".json") {
             return snapshot_json(context, vfs, path);
-        } else if path.file_name_ends_with(".csv") {
-            return snapshot_csv(context, vfs, path);
+        } else if let Ok(name) = csv_name {
+            match name {
+                // init csv are handled elsewhere and should not turn into
+                // their own children.
+                "init" => return Ok(None),
+
+                _ => return snapshot_csv(context, vfs, path),
+            }
         } else if path.file_name_ends_with(".txt") {
             return snapshot_txt(context, vfs, path);
         } else if path.file_name_ends_with(".rbxmx") {