Fix stale filesystem event path handling (AI-assisted)

AI-canary.txt

@@ -0,0 +1 @@
+This pull request is AI generated

CHANGELOG.md

@@ -35,9 +35,11 @@ Making a new release? Simply add the new header with the version and date undern
 * Fixed `rojo serve` silently stopping syncing file changes on Windows when the served project path was a verbatim (`\\?\`) path, because tree paths and file-watcher event paths were canonicalized to different forms. ([#1290])
 * Fixed `rojo sourcemap --absolute` emitting verbatim (`\\?\`) paths on Windows, which broke require types in luau-lsp. ([#1290])
 * The plugin now disables the `Check for Updates` setting if you block access to `api.github.com`. ([#1297])
+* Fixed `rojo serve` crashing when queued filesystem events refer to paths whose ancestors have already been removed. ([#1314])
 
 [#1290]: https://github.com/rojo-rbx/rojo/pull/1290
 [#1297]: https://github.com/rojo-rbx/rojo/pull/1297
+[#1314]: https://github.com/rojo-rbx/rojo/issues/1314
 
 ## [7.7.0] (July 1st, 2026)
 

src/change_processor.rs

@@ -2,9 +2,9 @@ use crossbeam_channel::{select, Receiver, RecvError, Sender};
 use jod_thread::JoinHandle;
 use memofs::{IoResultExt, Vfs, VfsEvent};
 use rbx_dom_weak::types::{Ref, Variant};
-use std::path::PathBuf;
 use std::{
-    fs,
+    fs, io,
+    path::{Path, PathBuf},
     sync::{Arc, Mutex},
 };
 
@@ -113,6 +113,31 @@ struct JobThreadContext {
     message_queue: Arc<MessageQueue<AppliedPatchSet>>,
 }
 
+/// Canonicalizes as much of an event path as still exists.
+///
+/// Filesystem events can become stale while they wait to be processed. For
+/// example, recursively removing a directory can remove a child's parent
+/// before the child's event is handled. Canonicalizing the nearest existing
+/// ancestor preserves the normalized prefix used by the tree while allowing
+/// the missing suffix to still drive reconciliation.
+fn canonicalize_event_path(vfs: &Vfs, path: &Path) -> io::Result<PathBuf> {
+    let mut ancestor = path;
+
+    loop {
+        match vfs.canonicalize(ancestor) {
+            Ok(canonical_ancestor) => {
+                let missing_suffix = path.strip_prefix(ancestor).map_err(io::Error::other)?;
+                return Ok(canonical_ancestor.join(missing_suffix));
+            }
+            Err(err) if err.kind() == io::ErrorKind::NotFound => match ancestor.parent() {
+                Some(parent) => ancestor = parent,
+                None => return Err(err),
+            },
+            Err(err) => return Err(err),
+        }
+    }
+}
+
 impl JobThreadContext {
     /// Computes and applies patches to the DOM for a given file path.
     ///
@@ -168,16 +193,18 @@ impl JobThreadContext {
         // For a given VFS event, we might have many changes to different parts
         // of the tree. Calculate and apply all of these changes.
         let applied_patches = match event {
-            VfsEvent::Create(path) | VfsEvent::Write(path) => {
-                self.apply_patches(self.vfs.canonicalize(&path).unwrap())
-            }
-            VfsEvent::Remove(path) => {
-                // MemoFS does not track parent removals yet, so we can canonicalize
-                // the parent path safely and then append the removed path's file name.
-                let parent = path.parent().unwrap();
-                let file_name = path.file_name().unwrap();
-                let parent_normalized = self.vfs.canonicalize(parent).unwrap();
-                self.apply_patches(parent_normalized.join(file_name))
+            VfsEvent::Create(path) | VfsEvent::Write(path) | VfsEvent::Remove(path) => {
+                match canonicalize_event_path(&self.vfs, &path) {
+                    Ok(path) => self.apply_patches(path),
+                    Err(err) => {
+                        log::error!(
+                            "Could not canonicalize filesystem event path {}: {}",
+                            path.display(),
+                            err
+                        );
+                        Vec::new()
+                    }
+                }
             }
             _ => {
                 log::warn!("Unhandled VFS event: {:?}", event);
@@ -383,3 +410,42 @@ fn compute_and_apply_changes(tree: &mut RojoTree, vfs: &Vfs, id: Ref) -> Option<
 
     Some(applied_patch_set)
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    use memofs::{InMemoryFs, VfsSnapshot};
+
+    use crate::snapshot::InstanceSnapshot;
+
+    fn stale_event_context() -> JobThreadContext {
+        let mut backend = InMemoryFs::new();
+        backend
+            .load_snapshot("/project", VfsSnapshot::empty_dir())
+            .unwrap();
+
+        JobThreadContext {
+            tree: Arc::new(Mutex::new(RojoTree::new(InstanceSnapshot::new()))),
+            vfs: Arc::new(Vfs::new(backend)),
+            message_queue: Arc::new(MessageQueue::new()),
+        }
+    }
+
+    #[test]
+    fn stale_remove_event_does_not_panic_when_parent_was_removed() {
+        let context = stale_event_context();
+        let path = PathBuf::from("/project/out/server/deep/file.luau");
+
+        assert_eq!(canonicalize_event_path(&context.vfs, &path).unwrap(), path);
+
+        context.handle_vfs_event(VfsEvent::Remove(path));
+    }
+
+    #[test]
+    fn stale_write_event_does_not_panic_when_path_was_removed() {
+        let context = stale_event_context();
+
+        context.handle_vfs_event(VfsEvent::Write("/project/out/server/deep/file.luau".into()));
+    }
+}