Implement new oneshot Vfs for CLI commands and enhance JSON5 serialization

- Added `new_oneshot` method to the Vfs struct, providing a backend suitable for one-time operations without file watching.
- Updated CLI commands (`fmt_project` and `syncback`) to utilize the new oneshot Vfs, improving error handling during file operations.
- Enhanced JSON5 serialization by introducing a custom serializer that directly builds a tree structure, improving performance and maintaining sorted keys.
- Improved error logging in JSON serialization to provide more context on failures.

src/cli/fmt_project.rs

@@ -18,8 +18,8 @@ pub struct FmtProjectCommand {
 
 impl FmtProjectCommand {
     pub fn run(self) -> anyhow::Result<()> {
-        let vfs = Vfs::new_default();
-        vfs.set_watch_enabled(false);
+        // Use oneshot Vfs - file watching isn't needed for formatting
+        let vfs = Vfs::new_oneshot();
 
         let base_path = resolve_path(&self.project);
         let project = Project::load_fuzzy(&vfs, &base_path)?

src/cli/syncback.rs

@@ -69,8 +69,9 @@ impl SyncbackCommand {
             dom_start_timer.elapsed().as_secs_f32()
         );
 
-        let vfs = Vfs::new_default();
-        vfs.set_watch_enabled(false);
+        // Use oneshot Vfs for syncback - file watching isn't needed and
+        // watcher errors shouldn't terminate the process
+        let vfs = Vfs::new_oneshot();
 
         let project_start_timer = Instant::now();
         let session_old = ServeSession::new(vfs, path_old.clone())?;

src/snapshot_middleware/json_model.rs

@@ -83,12 +83,32 @@ pub fn syncback_json_model<'sync>(
         model.schema = old_inst.metadata().schema.clone();
     }
 
+    let serialized = match crate::json::to_vec_pretty_sorted(&model) {
+        Ok(bytes) => bytes,
+        Err(e) => {
+            // Provide more detail about what's in the model
+            let prop_details: Vec<_> = model
+                .properties
+                .iter()
+                .map(|(k, v)| format!("{}={:?}", k.as_str(), v))
+                .collect();
+            let attr_names: Vec<_> = model.attributes.keys().map(|k| k.as_str()).collect();
+            log::error!(
+                "Failed to serialize JSON model for class '{}': properties=[{}], attributes={:?}, error: {}",
+                model.class_name,
+                prop_details.join(", "),
+                attr_names,
+                e
+            );
+            return Err(e.context(format!(
+                "failed to serialize new JSON Model for class '{}'",
+                model.class_name
+            )));
+        }
+    };
+
     Ok(SyncbackReturn {
-        fs_snapshot: FsSnapshot::new().with_added_file(
-            &snapshot.path,
-            crate::json::to_vec_pretty_sorted(&model)
-                .context("failed to serialize new JSON Model")?,
-        ),
+        fs_snapshot: FsSnapshot::new().with_added_file(&snapshot.path, serialized),
         children: Vec::new(),
         removed_children: Vec::new(),
     })

src/web/api.rs

@@ -1823,14 +1823,14 @@ mod tests {
 
         #[test]
         fn test_float32() {
-            let variant = Variant::Float32(3.14);
+            let variant = Variant::Float32(3.125); // Use a non-constant value
             let result = variant_to_json(&variant);
             assert!(result.is_some());
         }
 
         #[test]
         fn test_float64() {
-            let variant = Variant::Float64(2.71828);
+            let variant = Variant::Float64(2.5); // Use a non-constant value
             let result = variant_to_json(&variant);
             assert!(result.is_some());
         }
@@ -1959,7 +1959,7 @@ mod tests {
             // Configuration creates a directory instead
             let json5_types = vec!["Part", "Frame", "TextLabel", "Model"];
             for class_name in json5_types {
-                let file_name = format!("Test.model.json5");
+                let file_name = "Test.model.json5";
                 assert!(
                     file_name.ends_with(".model.json5"),
                     "{} should create .model.json5 file",
@@ -2062,10 +2062,8 @@ mod tests {
                 .map(|e| &e.items);
 
             if let Some(enums) = run_context_enums {
-                if let Some(&client_value) = enums.get("Client") {
-                    // Verify the enum value exists
-                    assert!(client_value > 0 || client_value == 0);
-                }
+                // Verify the enum value exists - just getting it is the test
+                assert!(enums.get("Client").is_some());
             }
         }
 
@@ -2078,9 +2076,7 @@ mod tests {
                 .map(|e| &e.items);
 
             if let Some(enums) = run_context_enums {
-                if let Some(&server_value) = enums.get("Server") {
-                    assert!(server_value > 0 || server_value == 0);
-                }
+                assert!(enums.get("Server").is_some());
             }
         }
 
@@ -2093,9 +2089,7 @@ mod tests {
                 .map(|e| &e.items);
 
             if let Some(enums) = run_context_enums {
-                if let Some(&legacy_value) = enums.get("Legacy") {
-                    assert!(legacy_value > 0 || legacy_value == 0);
-                }
+                assert!(enums.get("Legacy").is_some());
             }
         }
 
@@ -2108,9 +2102,7 @@ mod tests {
                 .map(|e| &e.items);
 
             if let Some(enums) = run_context_enums {
-                if let Some(&plugin_value) = enums.get("Plugin") {
-                    assert!(plugin_value > 0 || plugin_value == 0);
-                }
+                assert!(enums.get("Plugin").is_some());
             }
         }
 
@@ -3675,7 +3667,7 @@ mod tests {
             // When syncing back children, duplicates should be skipped
             // This test verifies the filter_duplicate_children logic
 
-            let children_names = vec!["ChildA", "ChildB", "ChildA", "ChildC"];
+            let children_names = ["ChildA", "ChildB", "ChildA", "ChildC"];
             let unique: Vec<_> = children_names
                 .iter()
                 .filter(|&&name| children_names.iter().filter(|&&n| n == name).count() == 1)
@@ -3697,8 +3689,8 @@ mod tests {
             //   └─ Child2/
             //        └─ GrandChild (unique within its parent)
 
-            let child1_grandchildren = vec!["GrandChild", "GrandChild"];
-            let child2_grandchildren = vec!["GrandChild"];
+            let child1_grandchildren = ["GrandChild", "GrandChild"];
+            let child2_grandchildren = ["GrandChild"];
 
             // Child1's grandchildren have duplicates
             let child1_filtered: Vec<_> = child1_grandchildren
@@ -3741,7 +3733,7 @@ mod tests {
             // This simulates the is_tree_path_unique check
 
             // Scenario: Trying to add a script under a folder that has duplicate siblings
-            let parent_path_levels = vec![
+            let parent_path_levels = [
                 ("Root", vec!["FolderA", "FolderA"]), // Duplicate at this level!
             ];
 
@@ -3758,7 +3750,7 @@ mod tests {
         #[test]
         fn test_valid_parent_path() {
             // Valid parent path with no duplicates at any level
-            let parent_path_levels = vec![
+            let parent_path_levels = [
                 (
                     "ReplicatedStorage",
                     vec!["Workspace", "ReplicatedStorage", "ServerStorage"],