Graceful errors instead of crashing (#1267)

crates/memofs/CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## Unreleased Changes
 * Added `Vfs::canonicalize`. [#1201]
+* **Breaking:** `StdBackend::new` and `Vfs::new_default` now return `io::Result`, so a failure to create the filesystem watcher is reported as an error instead of panicking. The `Default` implementation for `StdBackend` has been removed as a result. [#1267]
+
+[#1267]: https://github.com/rojo-rbx/rojo/pull/1267
 
 ## 0.3.1 (2025-11-27)
 * Added `Vfs::exists`. [#1169]

crates/memofs/src/lib.rs

@@ -255,8 +255,11 @@ pub struct Vfs {
 
 impl Vfs {
     /// Creates a new `Vfs` with the default backend, `StdBackend`.
-    pub fn new_default() -> Self {
-        Self::new(StdBackend::new())
+    ///
+    /// Returns an error if the filesystem watcher could not be initialized,
+    /// which can happen in restricted or sandboxed environments.
+    pub fn new_default() -> io::Result<Self> {
+        Ok(Self::new(StdBackend::new()?))
     }
 
     /// Creates a new `Vfs` with the given backend.
@@ -639,7 +642,7 @@ mod test {
         let file_path = dir.path().join("file.txt");
         fs_err::write(&file_path, contents.to_string()).unwrap();
 
-        let vfs = Vfs::new(StdBackend::new());
+        let vfs = Vfs::new(StdBackend::new().unwrap());
         let canonicalized = vfs.canonicalize(&file_path).unwrap();
         assert_eq!(canonicalized, file_path.canonicalize().unwrap());
         assert_eq!(
@@ -653,7 +656,7 @@ mod test {
         let dir = tempfile::tempdir().unwrap();
         let file_path = dir.path().join("test");
 
-        let vfs = Vfs::new(StdBackend::new());
+        let vfs = Vfs::new(StdBackend::new().unwrap());
         let err = vfs.canonicalize(&file_path).unwrap_err();
         assert_eq!(err.kind(), io::ErrorKind::NotFound);
     }

crates/memofs/src/std_backend.rs

@@ -17,9 +17,9 @@ pub struct StdBackend {
 }
 
 impl StdBackend {
-    pub fn new() -> StdBackend {
+    pub fn new() -> io::Result<StdBackend> {
         let (notify_tx, notify_rx) = mpsc::channel();
-        let watcher = watcher(notify_tx, Duration::from_millis(50)).unwrap();
+        let watcher = watcher(notify_tx, Duration::from_millis(50)).map_err(io::Error::other)?;
 
         let (tx, rx) = crossbeam_channel::unbounded();
 
@@ -46,11 +46,11 @@ impl StdBackend {
             Result::<(), crossbeam_channel::SendError<VfsEvent>>::Ok(())
         });
 
-        Self {
+        Ok(Self {
             watcher,
             watcher_receiver: rx,
             watches: HashSet::new(),
-        }
+        })
     }
 }
 
@@ -134,9 +134,3 @@ impl VfsBackend for StdBackend {
         self.watcher.unwatch(path).map_err(io::Error::other)
     }
 }
-
-impl Default for StdBackend {
-    fn default() -> Self {
-        Self::new()
-    }
-}