linux watcher (#12615)

fixes https://github.com/zed-industries/zed/issues/12297
fixes https://github.com/zed-industries/zed/issues/11345

Release Notes:

- N/A

---------

Co-authored-by: Max <max@zed.dev>

crates/assistant/src/assistant_panel.rs

@@ -155,7 +155,7 @@ impl AssistantPanel {
                 cx.new_view::<Self>(|cx| {
                     const CONVERSATION_WATCH_DURATION: Duration = Duration::from_millis(100);
                     let _watch_saved_conversations = cx.spawn(move |this, mut cx| async move {
-                        let mut events = fs
+                        let (mut events, _) = fs
                             .watch(&CONVERSATIONS_DIR, CONVERSATION_WATCH_DURATION)
                             .await;
                         while events.next().await.is_some() {

crates/extension/src/extension_store.rs

@@ -351,7 +351,7 @@ impl ExtensionStore {
             let reload_tx = this.reload_tx.clone();
             let installed_dir = this.installed_dir.clone();
             async move {
-                let mut paths = fs.watch(&installed_dir, FS_WATCH_LATENCY).await;
+                let (mut paths, _) = fs.watch(&installed_dir, FS_WATCH_LATENCY).await;
                 while let Some(paths) = paths.next().await {
                     for path in paths {
                         let Ok(event_path) = path.strip_prefix(&installed_dir) else {

crates/fs/src/fs.rs

@@ -36,6 +36,11 @@ use smol::io::AsyncReadExt;
 #[cfg(any(test, feature = "test-support"))]
 use std::ffi::OsStr;
 
+pub trait Watcher: Send + Sync {
+    fn add(&self, path: &Path) -> Result<()>;
+    fn remove(&self, path: &Path) -> Result<()>;
+}
+
 #[async_trait::async_trait]
 pub trait Fs: Send + Sync {
     async fn create_dir(&self, path: &Path) -> Result<()>;
@@ -79,7 +84,10 @@ pub trait Fs: Send + Sync {
         &self,
         path: &Path,
         latency: Duration,
-    ) -> Pin<Box<dyn Send + Stream<Item = Vec<PathBuf>>>>;
+    ) -> (
+        Pin<Box<dyn Send + Stream<Item = Vec<PathBuf>>>>,
+        Arc<dyn Watcher>,
+    );
 
     fn open_repo(&self, abs_dot_git: &Path) -> Option<Arc<dyn GitRepository>>;
     fn is_fake(&self) -> bool;
@@ -126,6 +134,13 @@ pub struct RealFs {
     git_binary_path: Option<PathBuf>,
 }
 
+pub struct RealWatcher {
+    #[cfg(target_os = "linux")]
+    root_path: PathBuf,
+    #[cfg(target_os = "linux")]
+    fs_watcher: parking_lot::Mutex<notify::INotifyWatcher>,
+}
+
 impl RealFs {
     pub fn new(
         git_hosting_provider_registry: Arc<GitHostingProviderRegistry>,
@@ -409,7 +424,10 @@ impl Fs for RealFs {
         &self,
         path: &Path,
         latency: Duration,
-    ) -> Pin<Box<dyn Send + Stream<Item = Vec<PathBuf>>>> {
+    ) -> (
+        Pin<Box<dyn Send + Stream<Item = Vec<PathBuf>>>>,
+        Arc<dyn Watcher>,
+    ) {
         use fsevent::EventStream;
 
         let (tx, rx) = smol::channel::unbounded();
@@ -421,22 +439,76 @@ impl Fs for RealFs {
             });
         });
 
-        Box::pin(rx.chain(futures::stream::once(async move {
-            drop(handle);
-            vec![]
-        })))
+        (
+            Box::pin(rx.chain(futures::stream::once(async move {
+                drop(handle);
+                vec![]
+            }))),
+            Arc::new(RealWatcher {}),
+        )
     }
 
-    #[cfg(not(target_os = "macos"))]
+    #[cfg(target_os = "linux")]
     async fn watch(
         &self,
         path: &Path,
         _latency: Duration,
-    ) -> Pin<Box<dyn Send + Stream<Item = Vec<PathBuf>>>> {
-        use notify::{event::EventKind, event::ModifyKind, Watcher};
-        // todo(linux): This spawns two threads, while the macOS impl
-        // only spawns one. Can we use a OnceLock or some such to make
-        // this better
+    ) -> (
+        Pin<Box<dyn Send + Stream<Item = Vec<PathBuf>>>>,
+        Arc<dyn Watcher>,
+    ) {
+        let (tx, rx) = smol::channel::unbounded();
+
+        let file_watcher = notify::recommended_watcher({
+            let tx = tx.clone();
+            move |event: Result<notify::Event, _>| {
+                if let Some(event) = event.log_err() {
+                    tx.try_send(event.paths).ok();
+                }
+            }
+        })
+        .expect("Could not start file watcher");
+
+        let watcher = Arc::new(RealWatcher {
+            root_path: path.to_path_buf(),
+            fs_watcher: parking_lot::Mutex::new(file_watcher),
+        });
+
+        watcher.add(path).ok(); // Ignore "file doesn't exist error" and rely on parent watcher.
+
+        // watch the parent dir so we can tell when settings.json is created
+        if let Some(parent) = path.parent() {
+            watcher.add(parent).log_err();
+        }
+
+        (
+            Box::pin(rx.filter_map({
+                let watcher = watcher.clone();
+                move |mut paths| {
+                    paths.retain(|path| path.starts_with(&watcher.root_path));
+                    async move {
+                        if paths.is_empty() {
+                            None
+                        } else {
+                            Some(paths)
+                        }
+                    }
+                }
+            })),
+            watcher,
+        )
+    }
+
+    #[cfg(target_os = "windows")]
+    async fn watch(
+        &self,
+        path: &Path,
+        _latency: Duration,
+    ) -> (
+        Pin<Box<dyn Send + Stream<Item = Vec<PathBuf>>>>,
+        Arc<dyn Watcher>,
+    ) {
+        use notify::Watcher;
 
         let (tx, rx) = smol::channel::unbounded();
 
@@ -452,56 +524,15 @@ impl Fs for RealFs {
 
         file_watcher
             .watch(path, notify::RecursiveMode::Recursive)
-            .ok(); // It's ok if this fails, the parent watcher will add it.
+            .log_err();
 
-        let mut parent_watcher = notify::recommended_watcher({
-            let watched_path = path.to_path_buf();
-            let tx = tx.clone();
-            move |event: Result<notify::Event, _>| {
-                if let Some(event) = event.ok() {
-                    if event.paths.into_iter().any(|path| *path == watched_path) {
-                        match event.kind {
-                            EventKind::Modify(ev) => {
-                                if matches!(ev, ModifyKind::Name(_)) {
-                                    file_watcher
-                                        .watch(
-                                            watched_path.as_path(),
-                                            notify::RecursiveMode::Recursive,
-                                        )
-                                        .log_err();
-                                    let _ = tx.try_send(vec![watched_path.clone()]).ok();
-                                }
-                            }
-                            EventKind::Create(_) => {
-                                file_watcher
-                                    .watch(watched_path.as_path(), notify::RecursiveMode::Recursive)
-                                    .log_err();
-                                let _ = tx.try_send(vec![watched_path.clone()]).ok();
-                            }
-                            EventKind::Remove(_) => {
-                                file_watcher.unwatch(&watched_path).log_err();
-                                let _ = tx.try_send(vec![watched_path.clone()]).ok();
-                            }
-                            _ => {}
-                        }
-                    }
-                }
-            }
-        })
-        .expect("Could not start file watcher");
-
-        parent_watcher
-            .watch(
-                path.parent()
-                    .expect("Watching root is probably not what you want"),
-                notify::RecursiveMode::NonRecursive,
-            )
-            .expect("Could not start watcher on parent directory");
-
-        Box::pin(rx.chain(futures::stream::once(async move {
-            drop(parent_watcher);
-            vec![]
-        })))
+        (
+            Box::pin(rx.chain(futures::stream::once(async move {
+                drop(file_watcher);
+                vec![]
+            }))),
+            Arc::new(RealWatcher {}),
+        )
     }
 
     fn open_repo(&self, dotgit_path: &Path) -> Option<Arc<dyn GitRepository>> {
@@ -560,6 +591,36 @@ impl Fs for RealFs {
     }
 }
 
+#[cfg(not(target_os = "linux"))]
+impl Watcher for RealWatcher {
+    fn add(&self, _: &Path) -> Result<()> {
+        Ok(())
+    }
+
+    fn remove(&self, _: &Path) -> Result<()> {
+        Ok(())
+    }
+}
+
+#[cfg(target_os = "linux")]
+impl Watcher for RealWatcher {
+    fn add(&self, path: &Path) -> Result<()> {
+        use notify::Watcher;
+
+        self.fs_watcher
+            .lock()
+            .watch(path, notify::RecursiveMode::NonRecursive)?;
+        Ok(())
+    }
+
+    fn remove(&self, path: &Path) -> Result<()> {
+        use notify::Watcher;
+
+        self.fs_watcher.lock().unwatch(path)?;
+        Ok(())
+    }
+}
+
 #[cfg(any(test, feature = "test-support"))]
 pub struct FakeFs {
     // Use an unfair lock to ensure tests are deterministic.
@@ -1073,6 +1134,20 @@ impl FakeFsEntry {
     }
 }
 
+#[cfg(any(test, feature = "test-support"))]
+struct FakeWatcher {}
+
+#[cfg(any(test, feature = "test-support"))]
+impl Watcher for FakeWatcher {
+    fn add(&self, _: &Path) -> Result<()> {
+        Ok(())
+    }
+
+    fn remove(&self, _: &Path) -> Result<()> {
+        Ok(())
+    }
+}
+
 #[cfg(any(test, feature = "test-support"))]
 #[async_trait::async_trait]
 impl Fs for FakeFs {
@@ -1468,20 +1543,26 @@ impl Fs for FakeFs {
         &self,
         path: &Path,
         _: Duration,
-    ) -> Pin<Box<dyn Send + Stream<Item = Vec<PathBuf>>>> {
+    ) -> (
+        Pin<Box<dyn Send + Stream<Item = Vec<PathBuf>>>>,
+        Arc<dyn Watcher>,
+    ) {
         self.simulate_random_delay().await;
         let (tx, rx) = smol::channel::unbounded();
         self.state.lock().event_txs.push(tx);
         let path = path.to_path_buf();
         let executor = self.executor.clone();
-        Box::pin(futures::StreamExt::filter(rx, move |events| {
-            let result = events.iter().any(|evt_path| evt_path.starts_with(&path));
-            let executor = executor.clone();
-            async move {
-                executor.simulate_random_delay().await;
-                result
-            }
-        }))
+        (
+            Box::pin(futures::StreamExt::filter(rx, move |events| {
+                let result = events.iter().any(|evt_path| evt_path.starts_with(&path));
+                let executor = executor.clone();
+                async move {
+                    executor.simulate_random_delay().await;
+                    result
+                }
+            })),
+            Arc::new(FakeWatcher {}),
+        )
     }
 
     fn open_repo(&self, abs_dot_git: &Path) -> Option<Arc<dyn GitRepository>> {

crates/settings/src/settings_file.rs

@@ -38,7 +38,7 @@ pub fn watch_config_file(
     let (tx, rx) = mpsc::unbounded();
     executor
         .spawn(async move {
-            let events = fs.watch(&path, Duration::from_millis(100)).await;
+            let (events, _) = fs.watch(&path, Duration::from_millis(100)).await;
             futures::pin_mut!(events);
 
             let contents = fs.load(&path).await.unwrap_or_default();

crates/worktree/src/worktree.rs

@@ -8,15 +8,15 @@ use anyhow::{anyhow, Context as _, Result};
 use client::{proto, Client};
 use clock::ReplicaId;
 use collections::{HashMap, HashSet, VecDeque};
-use fs::Fs;
 use fs::{copy_recursive, RemoveOptions};
-use futures::stream::select;
+use fs::{Fs, Watcher};
 use futures::{
     channel::{
         mpsc::{self, UnboundedSender},
         oneshot,
     },
     select_biased,
+    stream::select,
     task::Poll,
     FutureExt as _, Stream, StreamExt,
 };
@@ -700,32 +700,42 @@ fn start_background_scan_tasks(
     let (scan_states_tx, mut scan_states_rx) = mpsc::unbounded();
     let background_scanner = cx.background_executor().spawn({
         let abs_path = if cfg!(target_os = "windows") {
-            abs_path.canonicalize().unwrap_or_else(|_| abs_path.to_path_buf())
+            abs_path
+                .canonicalize()
+                .unwrap_or_else(|_| abs_path.to_path_buf())
         } else {
             abs_path.to_path_buf()
         };
         let background = cx.background_executor().clone();
         async move {
-            let events = fs.watch(&abs_path, FS_WATCH_LATENCY).await;
+            let (events, watcher) = fs.watch(&abs_path, FS_WATCH_LATENCY).await;
             let case_sensitive = fs.is_case_sensitive().await.unwrap_or_else(|e| {
-                log::error!(
-                    "Failed to determine whether filesystem is case sensitive (falling back to true) due to error: {e:#}"
-                );
+                log::error!("Failed to determine whether filesystem is case sensitive: {e:#}");
                 true
             });
 
-            BackgroundScanner::new(
-                snapshot,
-                next_entry_id,
+            let mut scanner = BackgroundScanner {
                 fs,
-                case_sensitive,
-                scan_states_tx,
-                background,
+                fs_case_sensitive: case_sensitive,
+                status_updates_tx: scan_states_tx,
+                executor: background,
                 scan_requests_rx,
                 path_prefixes_to_scan_rx,
-            )
-            .run(events)
-            .await;
+                next_entry_id,
+                state: Mutex::new(BackgroundScannerState {
+                    prev_snapshot: snapshot.snapshot.clone(),
+                    snapshot,
+                    scanned_dirs: Default::default(),
+                    path_prefixes_to_scan: Default::default(),
+                    paths_to_scan: Default::default(),
+                    removed_entry_ids: Default::default(),
+                    changed_paths: Default::default(),
+                }),
+                phase: BackgroundScannerPhase::InitialScan,
+                watcher,
+            };
+
+            scanner.run(events).await;
         }
     });
     let scan_state_updater = cx.spawn(|this, mut cx| async move {
@@ -3327,6 +3337,7 @@ struct BackgroundScanner {
     path_prefixes_to_scan_rx: channel::Receiver<Arc<Path>>,
     next_entry_id: Arc<AtomicUsize>,
     phase: BackgroundScannerPhase,
+    watcher: Arc<dyn Watcher>,
 }
 
 #[derive(PartialEq)]
@@ -3337,38 +3348,6 @@ enum BackgroundScannerPhase {
 }
 
 impl BackgroundScanner {
-    #[allow(clippy::too_many_arguments)]
-    fn new(
-        snapshot: LocalSnapshot,
-        next_entry_id: Arc<AtomicUsize>,
-        fs: Arc<dyn Fs>,
-        fs_case_sensitive: bool,
-        status_updates_tx: UnboundedSender<ScanState>,
-        executor: BackgroundExecutor,
-        scan_requests_rx: channel::Receiver<ScanRequest>,
-        path_prefixes_to_scan_rx: channel::Receiver<Arc<Path>>,
-    ) -> Self {
-        Self {
-            fs,
-            fs_case_sensitive,
-            status_updates_tx,
-            executor,
-            scan_requests_rx,
-            path_prefixes_to_scan_rx,
-            next_entry_id,
-            state: Mutex::new(BackgroundScannerState {
-                prev_snapshot: snapshot.snapshot.clone(),
-                snapshot,
-                scanned_dirs: Default::default(),
-                path_prefixes_to_scan: Default::default(),
-                paths_to_scan: Default::default(),
-                removed_entry_ids: Default::default(),
-                changed_paths: Default::default(),
-            }),
-            phase: BackgroundScannerPhase::InitialScan,
-        }
-    }
-
     async fn run(&mut self, mut fs_events_rx: Pin<Box<dyn Send + Stream<Item = Vec<PathBuf>>>>) {
         use futures::FutureExt as _;
 
@@ -3396,7 +3375,7 @@ impl BackgroundScanner {
                     if let Some(ancestor_dot_git) =
                         self.fs.canonicalize(&ancestor_dot_git).await.log_err()
                     {
-                        let ancestor_git_events =
+                        let (ancestor_git_events, _) =
                             self.fs.watch(&ancestor_dot_git, FS_WATCH_LATENCY).await;
                         fs_events_rx = select(fs_events_rx, ancestor_git_events).boxed();
 
@@ -3987,6 +3966,7 @@ impl BackgroundScanner {
         }
 
         state.populate_dir(&job.path, new_entries, new_ignore);
+        self.watcher.add(job.abs_path.as_ref()).log_err();
 
         for new_job in new_jobs.into_iter().flatten() {
             job.scan_queue

crates/zed/src/main.rs

@@ -881,7 +881,7 @@ fn load_user_themes_in_background(fs: Arc<dyn fs::Fs>, cx: &mut AppContext) {
 fn watch_themes(fs: Arc<dyn fs::Fs>, cx: &mut AppContext) {
     use std::time::Duration;
     cx.spawn(|cx| async move {
-        let mut events = fs
+        let (mut events, _) = fs
             .watch(&paths::THEMES_DIR.clone(), Duration::from_millis(100))
             .await;
 
@@ -920,7 +920,7 @@ fn watch_languages(fs: Arc<dyn fs::Fs>, languages: Arc<LanguageRegistry>, cx: &m
     };
 
     cx.spawn(|_| async move {
-        let mut events = fs.watch(path.as_path(), Duration::from_millis(100)).await;
+        let (mut events, _) = fs.watch(path.as_path(), Duration::from_millis(100)).await;
         while let Some(event) = events.next().await {
             let has_language_file = event.iter().any(|path| {
                 path.extension()
@@ -954,7 +954,7 @@ fn watch_file_types(fs: Arc<dyn fs::Fs>, cx: &mut AppContext) {
     };
 
     cx.spawn(|cx| async move {
-        let mut events = fs.watch(path.as_path(), Duration::from_millis(100)).await;
+        let (mut events, _) = fs.watch(path.as_path(), Duration::from_millis(100)).await;
         while (events.next().await).is_some() {
             cx.update(|cx| {
                 FileIcons::update_global(cx, |file_types, _cx| {