use `Roots` in watcher

4 files changed, 274 insertions, 330 deletions

diff --git a/crates/ra_vfs/src/io.rs b/crates/ra_vfs/src/io.rs
index 83a021c2f..7ca1e9835 100644
--- a/crates/ra_vfs/src/io.rs
+++ b/crates/ra_vfs/src/io.rs
@@ -1,95 +1,72 @@
-use std::{
-    fmt, fs,
-    path::{Path, PathBuf},
-    sync::Arc,
-    thread,
-};
+use std::{fs, sync::Arc, thread};
 
 use crossbeam_channel::{Receiver, Sender};
-use parking_lot::Mutex;
 use relative_path::RelativePathBuf;
 use thread_worker::WorkerHandle;
 use walkdir::WalkDir;
 
 mod watcher;
 use watcher::Watcher;
-pub use watcher::WatcherChange;
 
-use crate::{RootFilter, VfsRoot};
+use crate::{RootFilter, Roots, VfsRoot};
 
 pub(crate) enum Task {
     AddRoot {
         root: VfsRoot,
-        path: PathBuf,
-        root_filter: Arc<RootFilter>,
-        nested_roots: Vec<PathBuf>,
-    },
-    /// this variant should only be created by the watcher
-    HandleChange(WatcherChange),
-    LoadChange(WatcherChange),
-    Watch {
-        dir: PathBuf,
-        root_filter: Arc<RootFilter>,
+        filter: Arc<RootFilter>,
     },
 }
 
 #[derive(Debug)]
-pub struct AddRootResult {
-    pub(crate) root: VfsRoot,
-    pub(crate) files: Vec<(RelativePathBuf, String)>,
-}
-
-#[derive(Debug)]
-pub enum WatcherChangeData {
-    Create { path: PathBuf, text: String },
-    Write { path: PathBuf, text: String },
-    Remove { path: PathBuf },
-}
-
 pub enum TaskResult {
-    AddRoot(AddRootResult),
-    HandleChange(WatcherChange),
-    LoadChange(WatcherChangeData),
-}
-
-impl fmt::Debug for TaskResult {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            TaskResult::AddRoot(..) => f.write_str("TaskResult::AddRoot(..)"),
-            TaskResult::HandleChange(c) => write!(f, "TaskResult::HandleChange({:?})", c),
-            TaskResult::LoadChange(c) => write!(f, "TaskResult::LoadChange({:?})", c),
-        }
-    }
+    BulkLoadRoot {
+        root: VfsRoot,
+        files: Vec<(RelativePathBuf, String)>,
+    },
+    AddSingleFile {
+        root: VfsRoot,
+        path: RelativePathBuf,
+        text: String,
+    },
+    ChangeSingleFile {
+        root: VfsRoot,
+        path: RelativePathBuf,
+        text: String,
+    },
+    RemoveSingleFile {
+        root: VfsRoot,
+        path: RelativePathBuf,
+    },
 }
 
 pub(crate) struct Worker {
     worker: thread_worker::Worker<Task, TaskResult>,
     worker_handle: WorkerHandle,
-    watcher: Arc<Mutex<Option<Watcher>>>,
 }
 
 impl Worker {
-    pub(crate) fn start() -> Worker {
-        let watcher = Arc::new(Mutex::new(None));
-        let watcher_clone = watcher.clone();
+    pub(crate) fn start(roots: Arc<Roots>) -> Worker {
         let (worker, worker_handle) =
             thread_worker::spawn("vfs", 128, move |input_receiver, output_sender| {
-                input_receiver
+                let mut watcher = match Watcher::start(roots, output_sender.clone()) {
+                    Ok(w) => Some(w),
+                    Err(e) => {
+                        log::error!("could not start watcher: {}", e);
+                        None
+                    }
+                };
+                let res = input_receiver
                     .into_iter()
-                    .filter_map(|t| handle_task(t, &watcher_clone))
-                    .try_for_each(|it| output_sender.send(it))
-                    .unwrap()
+                    .filter_map(|t| handle_task(t, &mut watcher))
+                    .try_for_each(|it| output_sender.send(it));
+                if let Some(watcher) = watcher {
+                    let _ = watcher.shutdown();
+                }
+                res.unwrap()
             });
-        match Watcher::start(worker.inp.clone()) {
-            Ok(w) => {
-                watcher.lock().replace(w);
-            }
-            Err(e) => log::error!("could not start watcher: {}", e),
-        };
         Worker {
             worker,
             worker_handle,
-            watcher,
         }
     }
 
@@ -102,72 +79,31 @@ impl Worker {
     }
 
     pub(crate) fn shutdown(self) -> thread::Result<()> {
-        if let Some(watcher) = self.watcher.lock().take() {
-            let _ = watcher.shutdown();
-        }
         let _ = self.worker.shutdown();
         self.worker_handle.shutdown()
     }
 }
 
-fn watch(
-    watcher: &Arc<Mutex<Option<Watcher>>>,
-    dir: &Path,
-    filter_entry: &RootFilter,
-    emit_for_existing: bool,
-) {
-    if let Some(watcher) = watcher.lock().as_mut() {
-        watcher.watch_recursive(dir, filter_entry, emit_for_existing)
-    }
-}
-
-fn handle_task(task: Task, watcher: &Arc<Mutex<Option<Watcher>>>) -> Option<TaskResult> {
+fn handle_task(task: Task, watcher: &mut Option<Watcher>) -> Option<TaskResult> {
     match task {
-        Task::AddRoot {
-            root,
-            path,
-            root_filter,
-            nested_roots,
-        } => {
-            watch(watcher, &path, root_filter.as_ref(), false);
-            log::debug!("loading {} ...", path.as_path().display());
-            let files = load_root(
-                path.as_path(),
-                root_filter.as_ref(),
-                nested_roots.as_slice(),
-            );
-            log::debug!("... loaded {}", path.as_path().display());
-            Some(TaskResult::AddRoot(AddRootResult { root, files }))
-        }
-        Task::HandleChange(change) => {
-            // forward as is because Vfs has to decide if we should load it
-            Some(TaskResult::HandleChange(change))
-        }
-        Task::LoadChange(change) => {
-            log::debug!("loading {:?} ...", change);
-            load_change(change).map(TaskResult::LoadChange)
-        }
-        Task::Watch { dir, root_filter } => {
-            watch(watcher, &dir, root_filter.as_ref(), true);
-            None
+        Task::AddRoot { root, filter } => {
+            if let Some(watcher) = watcher {
+                watcher.watch_root(&filter)
+            }
+            log::debug!("loading {} ...", filter.root.as_path().display());
+            let files = load_root(filter.as_ref());
+            log::debug!("... loaded {}", filter.root.as_path().display());
+            Some(TaskResult::BulkLoadRoot { root, files })
         }
     }
 }
 
-fn load_root(
-    root: &Path,
-    root_filter: &RootFilter,
-    nested_roots: &[PathBuf],
-) -> Vec<(RelativePathBuf, String)> {
+fn load_root(filter: &RootFilter) -> Vec<(RelativePathBuf, String)> {
     let mut res = Vec::new();
-    for entry in WalkDir::new(root).into_iter().filter_entry(|entry| {
-        if entry.file_type().is_dir() && nested_roots.iter().any(|it| it == entry.path()) {
-            // do not load files of a nested root
-            false
-        } else {
-            root_filter.can_contain(entry.path()).is_some()
-        }
-    }) {
+    for entry in WalkDir::new(&filter.root)
+        .into_iter()
+        .filter_entry(filter.entry_filter())
+    {
         let entry = match entry {
             Ok(entry) => entry,
             Err(e) => {
@@ -186,42 +122,8 @@ fn load_root(
                 continue;
             }
         };
-        let path = RelativePathBuf::from_path(path.strip_prefix(root).unwrap()).unwrap();
+        let path = RelativePathBuf::from_path(path.strip_prefix(&filter.root).unwrap()).unwrap();
         res.push((path.to_owned(), text))
     }
     res
 }
-
-fn load_change(change: WatcherChange) -> Option<WatcherChangeData> {
-    let data = match change {
-        WatcherChange::Create(path) => {
-            if path.is_dir() {
-                return None;
-            }
-            let text = match fs::read_to_string(&path) {
-                Ok(text) => text,
-                Err(e) => {
-                    log::warn!("watcher error \"{}\": {}", path.display(), e);
-                    return None;
-                }
-            };
-            WatcherChangeData::Create { path, text }
-        }
-        WatcherChange::Write(path) => {
-            let text = match fs::read_to_string(&path) {
-                Ok(text) => text,
-                Err(e) => {
-                    log::warn!("watcher error \"{}\": {}", path.display(), e);
-                    return None;
-                }
-            };
-            WatcherChangeData::Write { path, text }
-        }
-        WatcherChange::Remove(path) => WatcherChangeData::Remove { path },
-        WatcherChange::Rescan => {
-            // this should be handled by Vfs::handle_task
-            return None;
-        }
-    };
-    Some(data)
-}
diff --git a/crates/ra_vfs/src/io/watcher.rs b/crates/ra_vfs/src/io/watcher.rs
index 68bb6b692..1d7ce2136 100644
--- a/crates/ra_vfs/src/io/watcher.rs
+++ b/crates/ra_vfs/src/io/watcher.rs
@@ -1,118 +1,72 @@
-use crate::{io, RootFilter};
+use crate::{io, RootFilter, Roots, VfsRoot};
 use crossbeam_channel::Sender;
 use drop_bomb::DropBomb;
 use notify::{DebouncedEvent, RecommendedWatcher, RecursiveMode, Watcher as NotifyWatcher};
+use parking_lot::Mutex;
 use std::{
+    fs,
     path::{Path, PathBuf},
-    sync::mpsc,
+    sync::{mpsc, Arc},
     thread,
     time::Duration,
 };
 use walkdir::WalkDir;
 
 #[derive(Debug)]
-pub enum WatcherChange {
-    Create(PathBuf),
-    Write(PathBuf),
-    Remove(PathBuf),
-    Rescan,
-}
-
-fn handle_change_event(
-    ev: DebouncedEvent,
-    sender: &Sender<io::Task>,
-) -> Result<(), Box<std::error::Error>> {
-    match ev {
-        DebouncedEvent::NoticeWrite(_)
-        | DebouncedEvent::NoticeRemove(_)
-        | DebouncedEvent::Chmod(_) => {
-            // ignore
-        }
-        DebouncedEvent::Rescan => {
-            sender.send(io::Task::HandleChange(WatcherChange::Rescan))?;
-        }
-        DebouncedEvent::Create(path) => {
-            sender.send(io::Task::HandleChange(WatcherChange::Create(path)))?;
-        }
-        DebouncedEvent::Write(path) => {
-            sender.send(io::Task::HandleChange(WatcherChange::Write(path)))?;
-        }
-        DebouncedEvent::Remove(path) => {
-            sender.send(io::Task::HandleChange(WatcherChange::Remove(path)))?;
-        }
-        DebouncedEvent::Rename(src, dst) => {
-            sender.send(io::Task::HandleChange(WatcherChange::Remove(src)))?;
-            sender.send(io::Task::HandleChange(WatcherChange::Create(dst)))?;
-        }
-        DebouncedEvent::Error(err, path) => {
-            // TODO should we reload the file contents?
-            log::warn!("watcher error \"{}\", {:?}", err, path);
-        }
-    }
-    Ok(())
+enum ChangeKind {
+    Create,
+    Write,
+    Remove,
 }
 
 const WATCHER_DELAY: Duration = Duration::from_millis(250);
 
 pub(crate) struct Watcher {
-    watcher: RecommendedWatcher,
     thread: thread::JoinHandle<()>,
     bomb: DropBomb,
-    sender: Sender<io::Task>,
+    watcher: Arc<Mutex<Option<RecommendedWatcher>>>,
 }
 
 impl Watcher {
     pub(crate) fn start(
-        output_sender: Sender<io::Task>,
+        roots: Arc<Roots>,
+        output_sender: Sender<io::TaskResult>,
     ) -> Result<Watcher, Box<std::error::Error>> {
         let (input_sender, input_receiver) = mpsc::channel();
-        let watcher = notify::watcher(input_sender, WATCHER_DELAY)?;
+        let watcher = Arc::new(Mutex::new(Some(notify::watcher(
+            input_sender,
+            WATCHER_DELAY,
+        )?)));
         let sender = output_sender.clone();
+        let watcher_clone = watcher.clone();
         let thread = thread::spawn(move || {
+            let worker = WatcherWorker {
+                roots,
+                watcher: watcher_clone,
+                sender,
+            };
             input_receiver
                 .into_iter()
                 // forward relevant events only
-                .try_for_each(|change| handle_change_event(change, &output_sender))
+                .try_for_each(|change| worker.handle_debounced_event(change))
                 .unwrap()
         });
         Ok(Watcher {
-            watcher,
             thread,
-            sender,
+            watcher,
             bomb: DropBomb::new(format!("Watcher was not shutdown")),
         })
     }
 
-    pub fn watch_recursive(&mut self, dir: &Path, filter: &RootFilter, emit_for_contents: bool) {
-        for res in WalkDir::new(dir)
+    pub fn watch_root(&mut self, filter: &RootFilter) {
+        for res in WalkDir::new(&filter.root)
             .into_iter()
-            .filter_entry(|entry| filter.can_contain(entry.path()).is_some())
+            .filter_entry(filter.entry_filter())
         {
             match res {
                 Ok(entry) => {
                     if entry.path().is_dir() {
-                        match self
-                            .watcher
-                            .watch(entry.path(), RecursiveMode::NonRecursive)
-                        {
-                            Ok(()) => log::debug!("watching \"{}\"", entry.path().display()),
-                            Err(e) => {
-                                log::warn!("could not watch \"{}\": {}", entry.path().display(), e)
-                            }
-                        }
-                    } else {
-                        if emit_for_contents && entry.depth() > 0 {
-                            // emit only for files otherwise we will cause watch_recursive to be called again with a dir that we are already watching
-                            // emit as create because we haven't seen it yet
-                            if let Err(e) =
-                                self.sender
-                                    .send(io::Task::HandleChange(WatcherChange::Create(
-                                        entry.path().to_path_buf(),
-                                    )))
-                            {
-                                log::warn!("watcher error: {}", e)
-                            }
-                        }
+                        watch_one(self.watcher.as_ref(), entry.path());
                     }
                 }
                 Err(e) => log::warn!("watcher error: {}", e),
@@ -122,7 +76,7 @@ impl Watcher {
 
     pub fn shutdown(mut self) -> thread::Result<()> {
         self.bomb.defuse();
-        drop(self.watcher);
+        drop(self.watcher.lock().take());
         let res = self.thread.join();
         match &res {
             Ok(()) => log::info!("... Watcher terminated with ok"),
@@ -131,3 +85,116 @@ impl Watcher {
         res
     }
 }
+
+struct WatcherWorker {
+    watcher: Arc<Mutex<Option<RecommendedWatcher>>>,
+    roots: Arc<Roots>,
+    sender: Sender<io::TaskResult>,
+}
+
+impl WatcherWorker {
+    fn handle_debounced_event(&self, ev: DebouncedEvent) -> Result<(), Box<std::error::Error>> {
+        match ev {
+            DebouncedEvent::NoticeWrite(_)
+            | DebouncedEvent::NoticeRemove(_)
+            | DebouncedEvent::Chmod(_) => {
+                // ignore
+            }
+            DebouncedEvent::Rescan => {
+                // TODO rescan all roots
+            }
+            DebouncedEvent::Create(path) => {
+                self.handle_change(path, ChangeKind::Create);
+            }
+            DebouncedEvent::Write(path) => {
+                self.handle_change(path, ChangeKind::Write);
+            }
+            DebouncedEvent::Remove(path) => {
+                self.handle_change(path, ChangeKind::Remove);
+            }
+            DebouncedEvent::Rename(src, dst) => {
+                self.handle_change(src, ChangeKind::Remove);
+                self.handle_change(dst, ChangeKind::Create);
+            }
+            DebouncedEvent::Error(err, path) => {
+                // TODO should we reload the file contents?
+                log::warn!("watcher error \"{}\", {:?}", err, path);
+            }
+        }
+        Ok(())
+    }
+
+    fn handle_change(&self, path: PathBuf, kind: ChangeKind) {
+        if let Err(e) = self.try_handle_change(path, kind) {
+            log::warn!("watcher error: {}", e)
+        }
+    }
+
+    fn try_handle_change(
+        &self,
+        path: PathBuf,
+        kind: ChangeKind,
+    ) -> Result<(), Box<std::error::Error>> {
+        let (root, rel_path) = match self.roots.find(&path) {
+            Some(x) => x,
+            None => return Ok(()),
+        };
+        match kind {
+            ChangeKind::Create => {
+                if path.is_dir() {
+                    self.watch_recursive(&path, root);
+                } else {
+                    let text = fs::read_to_string(&path)?;
+                    self.sender.send(io::TaskResult::AddSingleFile {
+                        root,
+                        path: rel_path,
+                        text,
+                    })?
+                }
+            }
+            ChangeKind::Write => {
+                let text = fs::read_to_string(&path)?;
+                self.sender.send(io::TaskResult::ChangeSingleFile {
+                    root,
+                    path: rel_path,
+                    text,
+                })?
+            }
+            ChangeKind::Remove => self.sender.send(io::TaskResult::RemoveSingleFile {
+                root,
+                path: rel_path,
+            })?,
+        }
+        Ok(())
+    }
+
+    fn watch_recursive(&self, dir: &Path, root: VfsRoot) {
+        let filter = &self.roots[root];
+        for res in WalkDir::new(dir)
+            .into_iter()
+            .filter_entry(|entry| filter.can_contain(entry.path()).is_some())
+        {
+            match res {
+                Ok(entry) => {
+                    if entry.path().is_dir() {
+                        watch_one(self.watcher.as_ref(), entry.path());
+                    } else {
+                        // emit only for files otherwise we will cause watch_recursive to be called again with a dir that we are already watching
+                        // emit as create because we haven't seen it yet
+                        self.handle_change(entry.path().to_path_buf(), ChangeKind::Create);
+                    }
+                }
+                Err(e) => log::warn!("watcher error: {}", e),
+            }
+        }
+    }
+}
+
+fn watch_one(watcher: &Mutex<Option<RecommendedWatcher>>, dir: &Path) {
+    if let Some(watcher) = watcher.lock().as_mut() {
+        match watcher.watch(dir, RecursiveMode::NonRecursive) {
+            Ok(()) => log::debug!("watching \"{}\"", dir.display()),
+            Err(e) => log::warn!("could not watch \"{}\": {}", dir.display(), e),
+        }
+    }
+}
diff --git a/crates/ra_vfs/src/lib.rs b/crates/ra_vfs/src/lib.rs
index cba3a463a..661892f8a 100644
--- a/crates/ra_vfs/src/lib.rs
+++ b/crates/ra_vfs/src/lib.rs
@@ -28,22 +28,25 @@ use crossbeam_channel::Receiver;
 use ra_arena::{impl_arena_id, Arena, RawId};
 use relative_path::{Component, RelativePath, RelativePathBuf};
 use rustc_hash::{FxHashMap, FxHashSet};
+use walkdir::DirEntry;
 
 pub use crate::io::TaskResult as VfsTask;
-use io::{Task, TaskResult, WatcherChange, WatcherChangeData, Worker};
+use io::{TaskResult, Worker};
 
 /// `RootFilter` is a predicate that checks if a file can belong to a root. If
 /// several filters match a file (nested dirs), the most nested one wins.
 pub(crate) struct RootFilter {
     root: PathBuf,
     filter: fn(&Path, &RelativePath) -> bool,
+    excluded_dirs: Vec<PathBuf>,
 }
 
 impl RootFilter {
-    fn new(root: PathBuf) -> RootFilter {
+    fn new(root: PathBuf, excluded_dirs: Vec<PathBuf>) -> RootFilter {
         RootFilter {
             root,
             filter: default_filter,
+            excluded_dirs,
         }
     }
     /// Check if this root can contain `path`. NB: even if this returns
@@ -56,6 +59,17 @@ impl RootFilter {
         }
         Some(rel_path)
     }
+
+    pub(crate) fn entry_filter<'a>(&'a self) -> impl FnMut(&DirEntry) -> bool + 'a {
+        move |entry: &DirEntry| {
+            if entry.path().is_dir() && self.excluded_dirs.iter().any(|it| it == entry.path()) {
+                // do not walk nested roots
+                false
+            } else {
+                self.can_contain(entry.path()).is_some()
+            }
+        }
+    }
 }
 
 pub(crate) fn default_filter(path: &Path, rel_path: &RelativePath) -> bool {
@@ -94,10 +108,22 @@ pub(crate) struct Roots {
 }
 
 impl Roots {
-    pub(crate) fn new() -> Roots {
-        Roots {
-            roots: Arena::default(),
+    pub(crate) fn new(mut paths: Vec<PathBuf>) -> Roots {
+        let mut roots = Arena::default();
+        // A hack to make nesting work.
+        paths.sort_by_key(|it| Reverse(it.as_os_str().len()));
+        for (i, path) in paths.iter().enumerate() {
+            let nested_roots = paths[..i]
+                .iter()
+                .filter(|it| it.starts_with(path))
+                .map(|it| it.clone())
+                .collect::<Vec<_>>();
+
+            let root_filter = Arc::new(RootFilter::new(path.clone(), nested_roots));
+
+            roots.alloc(root_filter.clone());
         }
+        Roots { roots }
     }
     pub(crate) fn find(&self, path: &Path) -> Option<(VfsRoot, RelativePathBuf)> {
         self.roots
@@ -135,36 +161,22 @@ impl fmt::Debug for Vfs {
 
 impl Vfs {
     pub fn new(roots: Vec<PathBuf>) -> (Vfs, Vec<VfsRoot>) {
-        let mut root_paths = roots;
-        let worker = io::Worker::start();
-
-        let mut roots = Roots::new();
+        let roots = Arc::new(Roots::new(roots));
+        let worker = io::Worker::start(roots.clone());
         let mut root2files = FxHashMap::default();
 
-        // A hack to make nesting work.
-        root_paths.sort_by_key(|it| Reverse(it.as_os_str().len()));
-        for (i, path) in root_paths.iter().enumerate() {
-            let root_filter = Arc::new(RootFilter::new(path.clone()));
-
-            let root = roots.alloc(root_filter.clone());
+        for (root, filter) in roots.iter() {
             root2files.insert(root, Default::default());
-
-            let nested_roots = root_paths[..i]
-                .iter()
-                .filter(|it| it.starts_with(path))
-                .map(|it| it.clone())
-                .collect::<Vec<_>>();
-
-            let task = io::Task::AddRoot {
-                root,
-                path: path.clone(),
-                root_filter,
-                nested_roots,
-            };
-            worker.sender().send(task).unwrap();
+            worker
+                .sender()
+                .send(io::Task::AddRoot {
+                    root,
+                    filter: filter.clone(),
+                })
+                .unwrap();
         }
         let res = Vfs {
-            roots: Arc::new(roots),
+            roots,
             files: Arena::default(),
             root2files,
             worker,
@@ -225,90 +237,46 @@ impl Vfs {
 
     pub fn handle_task(&mut self, task: io::TaskResult) {
         match task {
-            TaskResult::AddRoot(task) => {
-                let mut files = Vec::new();
+            TaskResult::BulkLoadRoot { root, files } => {
+                let mut cur_files = Vec::new();
                 // While we were scanning the root in the backgound, a file might have
                 // been open in the editor, so we need to account for that.
-                let exising = self.root2files[&task.root]
+                let exising = self.root2files[&root]
                     .iter()
                     .map(|&file| (self.files[file].path.clone(), file))
                     .collect::<FxHashMap<_, _>>();
-                for (path, text) in task.files {
+                for (path, text) in files {
                     if let Some(&file) = exising.get(&path) {
                         let text = Arc::clone(&self.files[file].text);
-                        files.push((file, path, text));
+                        cur_files.push((file, path, text));
                         continue;
                     }
                     let text = Arc::new(text);
-                    let file = self.add_file(task.root, path.clone(), Arc::clone(&text), false);
-                    files.push((file, path, text));
+                    let file = self.add_file(root, path.clone(), Arc::clone(&text), false);
+                    cur_files.push((file, path, text));
                 }
 
                 let change = VfsChange::AddRoot {
-                    root: task.root,
-                    files,
+                    root,
+                    files: cur_files,
                 };
                 self.pending_changes.push(change);
             }
-            TaskResult::HandleChange(change) => match &change {
-                WatcherChange::Create(path) if path.is_dir() => {
-                    if let Some((root, _path, _file)) = self.find_root(&path) {
-                        let root_filter = self.roots[root].clone();
-                        self.worker
-                            .sender()
-                            .send(Task::Watch {
-                                dir: path.to_path_buf(),
-                                root_filter,
-                            })
-                            .unwrap()
-                    }
-                }
-                WatcherChange::Create(path)
-                | WatcherChange::Remove(path)
-                | WatcherChange::Write(path) => {
-                    if self.should_handle_change(&path) {
-                        self.worker.sender().send(Task::LoadChange(change)).unwrap()
-                    }
-                }
-                WatcherChange::Rescan => {
-                    // TODO we should reload all files
-                }
-            },
-            TaskResult::LoadChange(change) => match change {
-                WatcherChangeData::Create { path, text }
-                | WatcherChangeData::Write { path, text } => {
-                    if let Some((root, path, file)) = self.find_root(&path) {
-                        if let Some(file) = file {
-                            self.do_change_file(file, text, false);
-                        } else {
-                            self.do_add_file(root, path, text, false);
-                        }
-                    }
-                }
-                WatcherChangeData::Remove { path } => {
-                    if let Some((root, path, file)) = self.find_root(&path) {
-                        if let Some(file) = file {
-                            self.do_remove_file(root, path, file, false);
-                        }
-                    }
+            TaskResult::AddSingleFile { root, path, text } => {
+                self.do_add_file(root, path, text, false);
+            }
+            TaskResult::ChangeSingleFile { root, path, text } => {
+                if let Some(file) = self.find_file(root, &path) {
+                    self.do_change_file(file, text, false);
+                } else {
+                    self.do_add_file(root, path, text, false);
                 }
-            },
-        }
-    }
-
-    fn should_handle_change(&self, path: &Path) -> bool {
-        if let Some((_root, _rel_path, file)) = self.find_root(&path) {
-            if let Some(file) = file {
-                if self.files[file].is_overlayed {
-                    // file is overlayed
-                    log::debug!("skipping overlayed \"{}\"", path.display());
-                    return false;
+            }
+            TaskResult::RemoveSingleFile { root, path } => {
+                if let Some(file) = self.find_file(root, &path) {
+                    self.do_remove_file(root, path, file, false);
                 }
             }
-            true
-        } else {
-            // file doesn't belong to any root
-            false
         }
     }
 
@@ -434,11 +402,15 @@ impl Vfs {
 
     fn find_root(&self, path: &Path) -> Option<(VfsRoot, RelativePathBuf, Option<VfsFile>)> {
         let (root, path) = self.roots.find(&path)?;
-        let file = self.root2files[&root]
+        let file = self.find_file(root, &path);
+        Some((root, path, file))
+    }
+
+    fn find_file(&self, root: VfsRoot, path: &RelativePath) -> Option<VfsFile> {
+        self.root2files[&root]
             .iter()
             .map(|&it| it)
-            .find(|&file| self.files[file].path == path);
-        Some((root, path, file))
+            .find(|&file| self.files[file].path == path)
     }
 }
 
diff --git a/crates/ra_vfs/tests/vfs.rs b/crates/ra_vfs/tests/vfs.rs
index bf44e97c5..8562c56b9 100644
--- a/crates/ra_vfs/tests/vfs.rs
+++ b/crates/ra_vfs/tests/vfs.rs
@@ -75,27 +75,31 @@ fn test_vfs_works() -> std::io::Result<()> {
     }
 
     fs::write(&dir.path().join("a/b/baz.rs"), "quux").unwrap();
-    // 2 tasks per change, HandleChange and then LoadChange
-    process_tasks(&mut vfs, 2);
+    process_tasks(&mut vfs, 1);
     assert_match!(
         vfs.commit_changes().as_slice(),
         [VfsChange::ChangeFile { text, .. }],
         assert_eq!(text.as_str(), "quux")
     );
 
-    vfs.change_file_overlay(&dir.path().join("a/b/baz.rs"), "m".to_string());
+    vfs.add_file_overlay(&dir.path().join("a/b/baz.rs"), "m".to_string());
     assert_match!(
         vfs.commit_changes().as_slice(),
         [VfsChange::ChangeFile { text, .. }],
         assert_eq!(text.as_str(), "m")
     );
 
+    // changing file on disk while overlayed doesn't generate a VfsChange
+    fs::write(&dir.path().join("a/b/baz.rs"), "corge").unwrap();
+    process_tasks(&mut vfs, 1);
+    assert_match!(vfs.commit_changes().as_slice(), []);
+
     // removing overlay restores data on disk
     vfs.remove_file_overlay(&dir.path().join("a/b/baz.rs"));
     assert_match!(
         vfs.commit_changes().as_slice(),
         [VfsChange::ChangeFile { text, .. }],
-        assert_eq!(text.as_str(), "quux")
+        assert_eq!(text.as_str(), "corge")
     );
 
     vfs.add_file_overlay(&dir.path().join("a/b/spam.rs"), "spam".to_string());
@@ -117,7 +121,7 @@ fn test_vfs_works() -> std::io::Result<()> {
 
     fs::create_dir_all(dir.path().join("a/sub1/sub2")).unwrap();
     fs::write(dir.path().join("a/sub1/sub2/new.rs"), "new hello").unwrap();
-    process_tasks(&mut vfs, 3);
+    process_tasks(&mut vfs, 1);
     assert_match!(
         vfs.commit_changes().as_slice(),
         [VfsChange::AddFile { text, path, .. }],
@@ -132,7 +136,7 @@ fn test_vfs_works() -> std::io::Result<()> {
         &dir.path().join("a/sub1/sub2/new1.rs"),
     )
     .unwrap();
-    process_tasks(&mut vfs, 4);
+    process_tasks(&mut vfs, 2);
     assert_match!(
         vfs.commit_changes().as_slice(),
         [VfsChange::RemoveFile {
@@ -150,17 +154,16 @@ fn test_vfs_works() -> std::io::Result<()> {
     );
 
     fs::remove_file(&dir.path().join("a/sub1/sub2/new1.rs")).unwrap();
-    process_tasks(&mut vfs, 2);
+    process_tasks(&mut vfs, 1);
     assert_match!(
         vfs.commit_changes().as_slice(),
         [VfsChange::RemoveFile { path, .. }],
         assert_eq!(path, "sub1/sub2/new1.rs")
     );
 
-    fs::create_dir_all(dir.path().join("a/target")).unwrap();
     // should be ignored
+    fs::create_dir_all(dir.path().join("a/target")).unwrap();
     fs::write(&dir.path().join("a/target/new.rs"), "ignore me").unwrap();
-    process_tasks(&mut vfs, 1); // 1 task because no LoadChange will happen, just HandleChange for dir creation
 
     assert_match!(
         vfs.task_receiver().try_recv(),