14 files changed, 234 insertions, 398 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 0a7128d0c..7ebe6e67f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -542,6 +542,15 @@ dependencies = [
 ]
 
 [[package]]
+name = "parking_lot"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "lock_api 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "parking_lot_core"
 version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -554,6 +563,18 @@ dependencies = [
 ]
 
 [[package]]
+name = "parking_lot_core"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.43 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc_version 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.6.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "percent-encoding"
 version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -701,10 +722,12 @@ dependencies = [
  "im 12.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "languageserver-types 0.53.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ra_analysis 0.1.0",
  "ra_editor 0.1.0",
  "ra_syntax 0.1.0",
  "ra_text_edit 0.1.0",
+ "ra_vfs 0.1.0",
  "rayon 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "relative-path 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1496,7 +1519,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum num_cpus 1.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "5a69d464bdc213aaaff628444e99578ede64e9c854025aa43b9796530afa9238"
 "checksum owning_ref 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "49a4b8ea2179e6a2e27411d3bca09ca6dd630821cf6894c6c7c8467a8ee7ef13"
 "checksum parking_lot 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)" = "f0802bff09003b291ba756dc7e79313e51cc31667e94afbe847def490424cde5"
+"checksum parking_lot 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9723236a9525c757d9725b993511e3fc941e33f27751942232f0058298297edf"
 "checksum parking_lot_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "ad7f7e6ebdc79edff6fdcb87a55b620174f7a989e3eb31b65231f4af57f00b8c"
+"checksum parking_lot_core 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "94c8c7923936b28d546dfd14d4472eaf34c99b14e1c973a32b3e6d4eb04298c9"
 "checksum percent-encoding 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "31010dd2e1ac33d5b46a5b413495239882813e0369f8ed8a5e266f173602f831"
 "checksum pest 2.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "a677051ad923732bb5c70f2d45f8985a96e3eee2e2bff86697e3b11b0c3fcfde"
 "checksum pest_derive 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "b76f477146419bc539a63f4ef40e902166cb43b3e51cecc71d9136fd12c567e7"
diff --git a/crates/ra_analysis/src/imp.rs b/crates/ra_analysis/src/imp.rs
index 51bcd5a73..54f38b285 100644
--- a/crates/ra_analysis/src/imp.rs
+++ b/crates/ra_analysis/src/imp.rs
@@ -43,14 +43,17 @@ impl AnalysisHostImpl {
     pub fn apply_change(&mut self, change: AnalysisChange) {
         log::info!("apply_change {:?}", change);
         // self.gc_syntax_trees();
+        for root_id in change.new_roots {
+            self.db
+                .query_mut(ra_db::SourceRootQuery)
+                .set(root_id, Default::default());
+        }
 
         for (root_id, root_change) in change.roots_changed {
             self.apply_root_change(root_id, root_change);
         }
         for (file_id, text) in change.files_changed {
-            self.db
-                .query_mut(ra_db::FileTextQuery)
-                .set(file_id, Arc::new(text))
+            self.db.query_mut(ra_db::FileTextQuery).set(file_id, text)
         }
         if !change.libraries_added.is_empty() {
             let mut libraries = Vec::clone(&self.db.libraries());
diff --git a/crates/ra_analysis/src/lib.rs b/crates/ra_analysis/src/lib.rs
index b806c974d..8882feca3 100644
--- a/crates/ra_analysis/src/lib.rs
+++ b/crates/ra_analysis/src/lib.rs
@@ -44,8 +44,9 @@ pub use ra_db::{
 
 #[derive(Default)]
 pub struct AnalysisChange {
+    new_roots: Vec<SourceRootId>,
     roots_changed: FxHashMap<SourceRootId, RootChange>,
-    files_changed: Vec<(FileId, String)>,
+    files_changed: Vec<(FileId, Arc<String>)>,
     libraries_added: Vec<LibraryData>,
     crate_graph: Option<CrateGraph>,
 }
@@ -93,6 +94,9 @@ impl AnalysisChange {
     pub fn new() -> AnalysisChange {
         AnalysisChange::default()
     }
+    pub fn add_root(&mut self, root_id: SourceRootId) {
+        self.new_roots.push(root_id);
+    }
     pub fn add_file(
         &mut self,
         root_id: SourceRootId,
@@ -111,7 +115,7 @@ impl AnalysisChange {
             .added
             .push(file);
     }
-    pub fn change_file(&mut self, file_id: FileId, new_text: String) {
+    pub fn change_file(&mut self, file_id: FileId, new_text: Arc<String>) {
         self.files_changed.push((file_id, new_text))
     }
     pub fn remove_file(&mut self, root_id: SourceRootId, file_id: FileId, path: RelativePathBuf) {
diff --git a/crates/ra_lsp_server/Cargo.toml b/crates/ra_lsp_server/Cargo.toml
index 4e8e09584..fc10096e5 100644
--- a/crates/ra_lsp_server/Cargo.toml
+++ b/crates/ra_lsp_server/Cargo.toml
@@ -25,6 +25,7 @@ cargo_metadata = "0.6.0"
 text_unit = { version = "0.1.2", features = ["serde"] }
 smol_str = { version = "0.1.5", features = ["serde"] }
 rustc-hash = "1.0"
+parking_lot = "0.7.0"
 
 thread_worker = { path = "../thread_worker" }
 ra_syntax = { path = "../ra_syntax" }
@@ -32,6 +33,7 @@ ra_editor = { path = "../ra_editor" }
 ra_text_edit = { path = "../ra_text_edit" }
 ra_analysis = { path = "../ra_analysis" }
 gen_lsp_server = { path = "../gen_lsp_server" }
+ra_vfs = { path = "../ra_vfs" }
 
 [dev-dependencies]
 tempdir = "0.3.7"
diff --git a/crates/ra_lsp_server/src/lib.rs b/crates/ra_lsp_server/src/lib.rs
index 1d7258c35..725b1258a 100644
--- a/crates/ra_lsp_server/src/lib.rs
+++ b/crates/ra_lsp_server/src/lib.rs
@@ -1,11 +1,9 @@
 mod caps;
 mod conv;
 mod main_loop;
-mod path_map;
 mod project_model;
 pub mod req;
 mod server_world;
-mod vfs;
 
 pub type Result<T> = ::std::result::Result<T, ::failure::Error>;
 pub use crate::{caps::server_capabilities, main_loop::main_loop, main_loop::LspError};
diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index 9d3f83b4c..7904545d3 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -1,7 +1,10 @@
 mod handlers;
 mod subscriptions;
 
-use std::path::PathBuf;
+use std::{
+    path::PathBuf,
+    sync::Arc,
+};
 
 use crossbeam_channel::{unbounded, select, Receiver, Sender};
 use gen_lsp_server::{
@@ -9,8 +12,8 @@ use gen_lsp_server::{
 };
 use languageserver_types::NumberOrString;
 use ra_analysis::{Canceled, FileId, LibraryData};
+use ra_vfs::{VfsTask};
 use rayon;
-use thread_worker::Worker;
 use threadpool::ThreadPool;
 use rustc_hash::FxHashSet;
 use serde::{de::DeserializeOwned, Serialize};
@@ -19,10 +22,9 @@ use failure_derive::Fail;
 
 use crate::{
     main_loop::subscriptions::Subscriptions,
-    project_model::{workspace_loader, CargoWorkspace},
+    project_model::{workspace_loader},
     req,
     server_world::{ServerWorld, ServerWorldState},
-    vfs::{self, FileEvent},
     Result,
 };
 
@@ -50,32 +52,42 @@ enum Task {
 
 pub fn main_loop(
     internal_mode: bool,
-    root: PathBuf,
+    ws_root: PathBuf,
     publish_decorations: bool,
     msg_receiver: &Receiver<RawMessage>,
     msg_sender: &Sender<RawMessage>,
 ) -> Result<()> {
     let pool = ThreadPool::new(8);
     let (task_sender, task_receiver) = unbounded::<Task>();
-    let (fs_worker, fs_watcher) = vfs::roots_loader();
     let (ws_worker, ws_watcher) = workspace_loader();
 
+    ws_worker.send(ws_root.clone());
+    // FIXME: support dynamic workspace loading.
+    let workspaces = match ws_worker.recv().unwrap() {
+        Ok(ws) => vec![ws],
+        Err(e) => {
+            log::warn!("loading workspace failed: {}", e);
+            Vec::new()
+        }
+    };
+    ws_worker.shutdown();
+    ws_watcher
+        .shutdown()
+        .map_err(|_| format_err!("ws watcher died"))?;
+    let mut state = ServerWorldState::new(ws_root.clone(), workspaces);
+
     log::info!("server initialized, serving requests");
-    let mut state = ServerWorldState::default();
 
     let mut pending_requests = FxHashSet::default();
     let mut subs = Subscriptions::new();
     let main_res = main_loop_inner(
         internal_mode,
         publish_decorations,
-        root,
         &pool,
         msg_sender,
         msg_receiver,
         task_sender,
         task_receiver.clone(),
-        fs_worker,
-        ws_worker,
         &mut state,
         &mut pending_requests,
         &mut subs,
@@ -88,12 +100,11 @@ pub fn main_loop(
     drop(pool);
     log::info!("...threadpool has finished");
 
-    let fs_res = fs_watcher.shutdown();
-    let ws_res = ws_watcher.shutdown();
+    let vfs = Arc::try_unwrap(state.vfs).expect("all snapshots should be dead");
+    let vfs_res = vfs.into_inner().shutdown();
 
     main_res?;
-    fs_res.map_err(|_| format_err!("fs watcher died"))?;
-    ws_res.map_err(|_| format_err!("ws watcher died"))?;
+    vfs_res.map_err(|_| format_err!("fs watcher died"))?;
 
     Ok(())
 }
@@ -101,28 +112,22 @@ pub fn main_loop(
 fn main_loop_inner(
     internal_mode: bool,
     publish_decorations: bool,
-    ws_root: PathBuf,
     pool: &ThreadPool,
     msg_sender: &Sender<RawMessage>,
     msg_receiver: &Receiver<RawMessage>,
     task_sender: Sender<Task>,
     task_receiver: Receiver<Task>,
-    fs_worker: Worker<PathBuf, (PathBuf, Vec<FileEvent>)>,
-    ws_worker: Worker<PathBuf, Result<CargoWorkspace>>,
     state: &mut ServerWorldState,
     pending_requests: &mut FxHashSet<u64>,
     subs: &mut Subscriptions,
 ) -> Result<()> {
     let (libdata_sender, libdata_receiver) = unbounded();
-    ws_worker.send(ws_root.clone());
-    fs_worker.send(ws_root.clone());
     loop {
         #[derive(Debug)]
         enum Event {
             Msg(RawMessage),
             Task(Task),
-            Fs(PathBuf, Vec<FileEvent>),
-            Ws(Result<CargoWorkspace>),
+            Vfs(VfsTask),
             Lib(LibraryData),
         }
         log::trace!("selecting");
@@ -132,77 +137,19 @@ fn main_loop_inner(
                 None => bail!("client exited without shutdown"),
             },
             recv(task_receiver, task) => Event::Task(task.unwrap()),
-            recv(fs_worker.out, events) => match events {
-                None => bail!("roots watcher died"),
-                Some((pb, events)) => Event::Fs(pb, events),
-            }
-            recv(ws_worker.out, ws) => match ws {
-                None => bail!("workspace watcher died"),
-                Some(ws) => Event::Ws(ws),
+            recv(state.vfs.read().task_receiver(), task) => match task {
+                None => bail!("vfs died"),
+                Some(task) => Event::Vfs(task),
             }
             recv(libdata_receiver, data) => Event::Lib(data.unwrap())
         };
         let mut state_changed = false;
         match event {
             Event::Task(task) => on_task(task, msg_sender, pending_requests),
-            Event::Fs(root, events) => {
-                log::info!("fs change, {}, {} events", root.display(), events.len());
-                if root == ws_root {
-                    state.apply_fs_changes(events);
-                } else {
-                    let (files, resolver) = state.events_to_files(events);
-                    let sender = libdata_sender.clone();
-                    pool.execute(move || {
-                        let start = ::std::time::Instant::now();
-                        log::info!("indexing {} ... ", root.display());
-                        let data = LibraryData::prepare(files, resolver);
-                        log::info!("indexed {:?} {}", start.elapsed(), root.display());
-                        sender.send(data);
-                    });
-                }
+            Event::Vfs(task) => {
+                state.vfs.write().handle_task(task);
                 state_changed = true;
             }
-            Event::Ws(ws) => match ws {
-                Ok(ws) => {
-                    let workspaces = vec![ws];
-                    feedback(internal_mode, "workspace loaded", msg_sender);
-                    for ws in workspaces.iter() {
-                        // Add each library as constant input. If library is
-                        // within the workspace, don't treat it as a library.
-                        //
-                        // HACK: If source roots are nested, pick the outer one.
-
-                        let mut roots = ws
-                            .packages()
-                            .filter(|pkg| !pkg.is_member(ws))
-                            .filter_map(|pkg| {
-                                let root = pkg.root(ws).to_path_buf();
-                                if root.starts_with(&ws_root) {
-                                    None
-                                } else {
-                                    Some(root)
-                                }
-                            })
-                            .collect::<Vec<_>>();
-                        roots.sort_by_key(|it| it.as_os_str().len());
-                        let unique = roots
-                            .iter()
-                            .enumerate()
-                            .filter(|&(idx, long)| {
-                                !roots[..idx].iter().any(|short| long.starts_with(short))
-                            })
-                            .map(|(_idx, root)| root);
-
-                        for root in unique {
-                            log::debug!("sending root, {}", root.display());
-                            fs_worker.send(root.to_owned());
-                        }
-                    }
-                    state.set_workspaces(workspaces);
-                    state_changed = true;
-                }
-                Err(e) => log::warn!("loading workspace failed: {}", e),
-            },
             Event::Lib(lib) => {
                 feedback(internal_mode, "library loaded", msg_sender);
                 state.add_lib(lib);
@@ -234,6 +181,18 @@ fn main_loop_inner(
             },
         };
 
+        for lib in state.process_changes() {
+            let (root, files) = lib;
+            let sender = libdata_sender.clone();
+            pool.execute(move || {
+                let start = ::std::time::Instant::now();
+                log::info!("indexing {:?} ... ", root);
+                let data = LibraryData::prepare(root, files);
+                log::info!("indexed {:?} {:?}", start.elapsed(), root);
+                sender.send(data);
+            });
+        }
+
         if state_changed {
             update_file_notifications_on_threadpool(
                 pool,
@@ -336,8 +295,13 @@ fn on_notification(
             let path = uri
                 .to_file_path()
                 .map_err(|()| format_err!("invalid uri: {}", uri))?;
-            let file_id = state.add_mem_file(path, params.text_document.text);
-            subs.add_sub(file_id);
+            if let Some(file_id) = state
+                .vfs
+                .write()
+                .add_file_overlay(&path, params.text_document.text)
+            {
+                subs.add_sub(FileId(file_id.0));
+            }
             return Ok(());
         }
         Err(not) => not,
@@ -353,7 +317,7 @@ fn on_notification(
                 .pop()
                 .ok_or_else(|| format_err!("empty changes"))?
                 .text;
-            state.change_mem_file(path.as_path(), text)?;
+            state.vfs.write().change_file_overlay(path.as_path(), text);
             return Ok(());
         }
         Err(not) => not,
@@ -364,8 +328,9 @@ fn on_notification(
             let path = uri
                 .to_file_path()
                 .map_err(|()| format_err!("invalid uri: {}", uri))?;
-            let file_id = state.remove_mem_file(path.as_path())?;
-            subs.remove_sub(file_id);
+            if let Some(file_id) = state.vfs.write().remove_file_overlay(path.as_path()) {
+                subs.remove_sub(FileId(file_id.0));
+            }
             let params = req::PublishDiagnosticsParams {
                 uri,
                 diagnostics: Vec::new(),
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index acca480c7..572ae7fb5 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -326,9 +326,9 @@ pub fn handle_runnables(
                 None => return Ok(None),
             };
             let file_id = world.analysis().crate_root(crate_id)?;
-            let path = world.path_map.get_path(file_id);
+            let path = world.vfs.read().file2path(ra_vfs::VfsFile(file_id.0));
             let res = world.workspaces.iter().find_map(|ws| {
-                let tgt = ws.target_by_root(path)?;
+                let tgt = ws.target_by_root(&path)?;
                 let res = CargoTargetSpec {
                     package: tgt.package(ws).name(ws).to_string(),
                     target: tgt.name(ws).to_string(),
diff --git a/crates/ra_lsp_server/src/path_map.rs b/crates/ra_lsp_server/src/path_map.rs
deleted file mode 100644
index 86cf29540..000000000
--- a/crates/ra_lsp_server/src/path_map.rs
+++ /dev/null
@@ -1,105 +0,0 @@
-use std::{
-    fmt,
-    path::{Component, Path, PathBuf},
-};
-
-use im;
-use ra_analysis::{FileId};
-use relative_path::RelativePath;
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum Root {
-    Workspace,
-    Lib,
-}
-
-#[derive(Default, Clone)]
-pub struct PathMap {
-    next_id: u32,
-    path2id: im::HashMap<PathBuf, FileId>,
-    id2path: im::HashMap<FileId, PathBuf>,
-    id2root: im::HashMap<FileId, Root>,
-}
-
-impl fmt::Debug for PathMap {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.write_str("PathMap { ... }")
-    }
-}
-
-impl PathMap {
-    pub fn get_or_insert(&mut self, path: PathBuf, root: Root) -> (bool, FileId) {
-        let mut inserted = false;
-        let file_id = self
-            .path2id
-            .get(path.as_path())
-            .map(|&id| id)
-            .unwrap_or_else(|| {
-                inserted = true;
-                let id = self.new_file_id();
-                self.insert(path, id, root);
-                id
-            });
-        (inserted, file_id)
-    }
-    pub fn get_id(&self, path: &Path) -> Option<FileId> {
-        self.path2id.get(path).cloned()
-    }
-    pub fn get_path(&self, file_id: FileId) -> &Path {
-        self.id2path.get(&file_id).unwrap().as_path()
-    }
-    pub fn get_root(&self, file_id: FileId) -> Root {
-        self.id2root[&file_id]
-    }
-    fn insert(&mut self, path: PathBuf, file_id: FileId, root: Root) {
-        self.path2id.insert(path.clone(), file_id);
-        self.id2path.insert(file_id, path.clone());
-        self.id2root.insert(file_id, root);
-    }
-
-    fn new_file_id(&mut self) -> FileId {
-        let id = FileId(self.next_id);
-        self.next_id += 1;
-        id
-    }
-}
-
-fn normalize(path: &Path) -> PathBuf {
-    let mut components = path.components().peekable();
-    let mut ret = if let Some(c @ Component::Prefix(..)) = components.peek().cloned() {
-        components.next();
-        PathBuf::from(c.as_os_str())
-    } else {
-        PathBuf::new()
-    };
-
-    for component in components {
-        match component {
-            Component::Prefix(..) => unreachable!(),
-            Component::RootDir => {
-                ret.push(component.as_os_str());
-            }
-            Component::CurDir => {}
-            Component::ParentDir => {
-                ret.pop();
-            }
-            Component::Normal(c) => {
-                ret.push(c);
-            }
-        }
-    }
-    ret
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-
-    #[test]
-    fn test_resolve() {
-        let mut m = PathMap::default();
-        let (_, id1) = m.get_or_insert(PathBuf::from("/foo"), Root::Workspace);
-        let (_, id2) = m.get_or_insert(PathBuf::from("/foo/bar.rs"), Root::Workspace);
-        assert_eq!(m.resolve(id1, &RelativePath::new("bar.rs")), Some(id2),)
-    }
-}
diff --git a/crates/ra_lsp_server/src/project_model.rs b/crates/ra_lsp_server/src/project_model.rs
index b881f8b6f..5852a157d 100644
--- a/crates/ra_lsp_server/src/project_model.rs
+++ b/crates/ra_lsp_server/src/project_model.rs
@@ -69,6 +69,7 @@ impl Package {
     pub fn targets<'a>(self, ws: &'a CargoWorkspace) -> impl Iterator<Item = Target> + 'a {
         ws.pkg(self).targets.iter().cloned()
     }
+    #[allow(unused)]
     pub fn is_member(self, ws: &CargoWorkspace) -> bool {
         ws.pkg(self).is_member
     }
diff --git a/crates/ra_lsp_server/src/server_world.rs b/crates/ra_lsp_server/src/server_world.rs
index c0d1338a2..f2fd09e85 100644
--- a/crates/ra_lsp_server/src/server_world.rs
+++ b/crates/ra_lsp_server/src/server_world.rs
@@ -1,154 +1,62 @@
 use std::{
-    fs,
-    path::{Path, PathBuf},
+    path::{PathBuf},
     sync::Arc,
 };
 
 use languageserver_types::Url;
 use ra_analysis::{
     Analysis, AnalysisChange, AnalysisHost, CrateGraph, FileId, LibraryData,
+    SourceRootId
 };
+use ra_vfs::{Vfs, VfsChange, VfsFile};
 use rustc_hash::FxHashMap;
-use failure::{bail, format_err};
+use relative_path::RelativePathBuf;
+use parking_lot::RwLock;
+use failure::{format_err};
 
 use crate::{
-    path_map::{PathMap, Root},
     project_model::{CargoWorkspace, TargetKind},
-    vfs::{FileEvent, FileEventKind},
     Result,
 };
 
-#[derive(Debug, Default)]
+#[derive(Debug)]
 pub struct ServerWorldState {
     pub workspaces: Arc<Vec<CargoWorkspace>>,
     pub analysis_host: AnalysisHost,
-    pub path_map: PathMap,
-    pub mem_map: FxHashMap<FileId, Option<String>>,
+    pub vfs: Arc<RwLock<Vfs>>,
 }
 
 pub struct ServerWorld {
     pub workspaces: Arc<Vec<CargoWorkspace>>,
     pub analysis: Analysis,
-    pub path_map: PathMap,
+    pub vfs: Arc<RwLock<Vfs>>,
 }
 
 impl ServerWorldState {
-    pub fn apply_fs_changes(&mut self, events: Vec<FileEvent>) {
+    pub fn new(root: PathBuf, workspaces: Vec<CargoWorkspace>) -> ServerWorldState {
         let mut change = AnalysisChange::new();
-        let mut inserted = false;
-        {
-            let pm = &mut self.path_map;
-            let mm = &mut self.mem_map;
-            events
-                .into_iter()
-                .map(|event| {
-                    let text = match event.kind {
-                        FileEventKind::Add(text) => text,
-                    };
-                    (event.path, text)
-                })
-                .map(|(path, text)| {
-                    let (ins, file_id) = pm.get_or_insert(path, Root::Workspace);
-                    inserted |= ins;
-                    (file_id, text)
-                })
-                .filter_map(|(file_id, text)| {
-                    if mm.contains_key(&file_id) {
-                        mm.insert(file_id, Some(text));
-                        None
-                    } else {
-                        Some((file_id, text))
-                    }
-                })
-                .for_each(|(file_id, text)| change.add_file(file_id, text));
-        }
-        if inserted {
-            change.set_file_resolver(Arc::new(self.path_map.clone()))
-        }
-        self.analysis_host.apply_change(change);
-    }
-    pub fn events_to_files(
-        &mut self,
-        events: Vec<FileEvent>,
-    ) -> (Vec<(FileId, String)>, Arc<FileResolver>) {
-        let files = {
-            let pm = &mut self.path_map;
-            events
-                .into_iter()
-                .map(|event| {
-                    let FileEventKind::Add(text) = event.kind;
-                    (event.path, text)
-                })
-                .map(|(path, text)| (pm.get_or_insert(path, Root::Lib).1, text))
-                .collect()
-        };
-        let resolver = Arc::new(self.path_map.clone());
-        (files, resolver)
-    }
-    pub fn add_lib(&mut self, data: LibraryData) {
-        let mut change = AnalysisChange::new();
-        change.add_library(data);
-        self.analysis_host.apply_change(change);
-    }
 
-    pub fn add_mem_file(&mut self, path: PathBuf, text: String) -> FileId {
-        let (inserted, file_id) = self.path_map.get_or_insert(path, Root::Workspace);
-        if self.path_map.get_root(file_id) != Root::Lib {
-            let mut change = AnalysisChange::new();
-            if inserted {
-                change.add_file(file_id, text);
-                change.set_file_resolver(Arc::new(self.path_map.clone()));
-            } else {
-                change.change_file(file_id, text);
+        let mut roots = Vec::new();
+        roots.push(root);
+        for ws in workspaces.iter() {
+            for pkg in ws.packages() {
+                roots.push(pkg.root(&ws).to_path_buf());
             }
-            self.analysis_host.apply_change(change);
         }
-        self.mem_map.insert(file_id, None);
-        file_id
-    }
-
-    pub fn change_mem_file(&mut self, path: &Path, text: String) -> Result<()> {
-        let file_id = self
-            .path_map
-            .get_id(path)
-            .ok_or_else(|| format_err!("change to unknown file: {}", path.display()))?;
-        if self.path_map.get_root(file_id) != Root::Lib {
-            let mut change = AnalysisChange::new();
-            change.change_file(file_id, text);
-            self.analysis_host.apply_change(change);
+        let (mut vfs, roots) = Vfs::new(roots);
+        for r in roots {
+            change.add_root(SourceRootId(r.0));
         }
-        Ok(())
-    }
 
-    pub fn remove_mem_file(&mut self, path: &Path) -> Result<FileId> {
-        let file_id = self
-            .path_map
-            .get_id(path)
-            .ok_or_else(|| format_err!("change to unknown file: {}", path.display()))?;
-        match self.mem_map.remove(&file_id) {
-            Some(_) => (),
-            None => bail!("unmatched close notification"),
-        };
-        // Do this via file watcher ideally.
-        let text = fs::read_to_string(path).ok();
-        if self.path_map.get_root(file_id) != Root::Lib {
-            let mut change = AnalysisChange::new();
-            if let Some(text) = text {
-                change.change_file(file_id, text);
-            }
-            self.analysis_host.apply_change(change);
-        }
-        Ok(file_id)
-    }
-    pub fn set_workspaces(&mut self, ws: Vec<CargoWorkspace>) {
         let mut crate_graph = CrateGraph::default();
         let mut pkg_to_lib_crate = FxHashMap::default();
         let mut pkg_crates = FxHashMap::default();
-        for ws in ws.iter() {
+        for ws in workspaces.iter() {
             for pkg in ws.packages() {
                 for tgt in pkg.targets(ws) {
                     let root = tgt.root(ws);
-                    if let Some(file_id) = self.path_map.get_id(root) {
+                    if let Some(file_id) = vfs.load(root) {
+                        let file_id = FileId(file_id.0);
                         let crate_id = crate_graph.add_crate_root(file_id);
                         if tgt.kind(ws) == TargetKind::Lib {
                             pkg_to_lib_crate.insert(pkg, crate_id);
@@ -170,16 +78,64 @@ impl ServerWorldState {
                 }
             }
         }
-        self.workspaces = Arc::new(ws);
-        let mut change = AnalysisChange::new();
         change.set_crate_graph(crate_graph);
+
+        let mut analysis_host = AnalysisHost::default();
+        analysis_host.apply_change(change);
+        ServerWorldState {
+            workspaces: Arc::new(workspaces),
+            analysis_host,
+            vfs: Arc::new(RwLock::new(vfs)),
+        }
+    }
+
+    /// Returns a vec of libraries
+    /// FIXME: better API here
+    pub fn process_changes(
+        &mut self,
+    ) -> Vec<(SourceRootId, Vec<(FileId, RelativePathBuf, Arc<String>)>)> {
+        let mut libs = Vec::new();
+        let mut change = AnalysisChange::new();
+        for c in self.vfs.write().commit_changes() {
+            match c {
+                VfsChange::AddRoot { root, files } => {
+                    let files = files
+                        .into_iter()
+                        .map(|(vfsfile, path, text)| (FileId(vfsfile.0), path, text))
+                        .collect();
+                    libs.push((SourceRootId(root.0), files));
+                }
+                VfsChange::AddFile {
+                    root,
+                    file,
+                    path,
+                    text,
+                } => {
+                    change.add_file(SourceRootId(root.0), FileId(file.0), path, text);
+                }
+                VfsChange::RemoveFile { root, file, path } => {
+                    change.remove_file(SourceRootId(root.0), FileId(file.0), path)
+                }
+                VfsChange::ChangeFile { file, text } => {
+                    change.change_file(FileId(file.0), text);
+                }
+            }
+        }
         self.analysis_host.apply_change(change);
+        libs
     }
+
+    pub fn add_lib(&mut self, data: LibraryData) {
+        let mut change = AnalysisChange::new();
+        change.add_library(data);
+        self.analysis_host.apply_change(change);
+    }
+
     pub fn snapshot(&self) -> ServerWorld {
         ServerWorld {
             workspaces: Arc::clone(&self.workspaces),
             analysis: self.analysis_host.analysis(),
-            path_map: self.path_map.clone(),
+            vfs: Arc::clone(&self.vfs),
         }
     }
 }
@@ -193,15 +149,18 @@ impl ServerWorld {
         let path = uri
             .to_file_path()
             .map_err(|()| format_err!("invalid uri: {}", uri))?;
-        self.path_map
-            .get_id(&path)
-            .ok_or_else(|| format_err!("unknown file: {}", path.display()))
+        let file = self
+            .vfs
+            .read()
+            .path2file(&path)
+            .ok_or_else(|| format_err!("unknown file: {}", path.display()))?;
+        Ok(FileId(file.0))
     }
 
     pub fn file_id_to_uri(&self, id: FileId) -> Result<Url> {
-        let path = self.path_map.get_path(id);
-        let url = Url::from_file_path(path)
-            .map_err(|()| format_err!("can't convert path to url: {}", path.display()))?;
+        let path = self.vfs.read().file2path(VfsFile(id.0));
+        let url = Url::from_file_path(&path)
+            .map_err(|_| format_err!("can't convert path to url: {}", path.display()))?;
         Ok(url)
     }
 }
diff --git a/crates/ra_lsp_server/src/vfs.rs b/crates/ra_lsp_server/src/vfs.rs
deleted file mode 100644
index fcf7693d8..000000000
--- a/crates/ra_lsp_server/src/vfs.rs
+++ /dev/null
@@ -1,67 +0,0 @@
-use std::{
-    fs,
-    path::{Path, PathBuf},
-};
-
-use walkdir::WalkDir;
-use thread_worker::{WorkerHandle, Worker};
-
-#[derive(Debug)]
-pub struct FileEvent {
-    pub path: PathBuf,
-    pub kind: FileEventKind,
-}
-
-#[derive(Debug)]
-pub enum FileEventKind {
-    Add(String),
-}
-
-pub fn roots_loader() -> (Worker<PathBuf, (PathBuf, Vec<FileEvent>)>, WorkerHandle) {
-    thread_worker::spawn::<PathBuf, (PathBuf, Vec<FileEvent>), _>(
-        "roots loader",
-        128,
-        |input_receiver, output_sender| {
-            input_receiver
-                .map(|path| {
-                    log::debug!("loading {} ...", path.as_path().display());
-                    let events = load_root(path.as_path());
-                    log::debug!("... loaded {}", path.as_path().display());
-                    (path, events)
-                })
-                .for_each(|it| output_sender.send(it))
-        },
-    )
-}
-
-fn load_root(path: &Path) -> Vec<FileEvent> {
-    let mut res = Vec::new();
-    for entry in WalkDir::new(path) {
-        let entry = match entry {
-            Ok(entry) => entry,
-            Err(e) => {
-                log::warn!("watcher error: {}", e);
-                continue;
-            }
-        };
-        if !entry.file_type().is_file() {
-            continue;
-        }
-        let path = entry.path();
-        if path.extension().and_then(|os| os.to_str()) != Some("rs") {
-            continue;
-        }
-        let text = match fs::read_to_string(path) {
-            Ok(text) => text,
-            Err(e) => {
-                log::warn!("watcher error: {}", e);
-                continue;
-            }
-        };
-        res.push(FileEvent {
-            path: path.to_owned(),
-            kind: FileEventKind::Add(text),
-        })
-    }
-    res
-}
diff --git a/crates/ra_vfs/src/io.rs b/crates/ra_vfs/src/io.rs
index 178c9beff..be400bae9 100644
--- a/crates/ra_vfs/src/io.rs
+++ b/crates/ra_vfs/src/io.rs
@@ -1,4 +1,5 @@
 use std::{
+    fmt,
     fs,
     path::{Path, PathBuf},
 };
@@ -20,6 +21,12 @@ pub struct TaskResult {
     pub(crate) files: Vec<(RelativePathBuf, String)>,
 }
 
+impl fmt::Debug for TaskResult {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str("TaskResult { ... }")
+    }
+}
+
 pub(crate) type Worker = thread_worker::Worker<Task, TaskResult>;
 
 pub(crate) fn start() -> (Worker, WorkerHandle) {
diff --git a/crates/ra_vfs/src/lib.rs b/crates/ra_vfs/src/lib.rs
index 6c1af5ef9..dc980c3d2 100644
--- a/crates/ra_vfs/src/lib.rs
+++ b/crates/ra_vfs/src/lib.rs
@@ -15,6 +15,7 @@ mod arena;
 mod io;
 
 use std::{
+    fmt,
     mem,
     thread,
     cmp::Reverse,
@@ -34,6 +35,8 @@ use crate::{
     arena::{ArenaId, Arena},
 };
 
+pub use crate::io::TaskResult as VfsTask;
+
 /// `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.
 struct RootFilter {
@@ -68,7 +71,7 @@ fn has_rs_extension(p: &Path) -> bool {
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
-pub struct VfsRoot(u32);
+pub struct VfsRoot(pub u32);
 
 impl ArenaId for VfsRoot {
     fn from_u32(idx: u32) -> VfsRoot {
@@ -80,7 +83,7 @@ impl ArenaId for VfsRoot {
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
-pub struct VfsFile(u32);
+pub struct VfsFile(pub u32);
 
 impl ArenaId for VfsFile {
     fn from_u32(idx: u32) -> VfsFile {
@@ -106,8 +109,14 @@ pub struct Vfs {
     worker_handle: WorkerHandle,
 }
 
+impl fmt::Debug for Vfs {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str("Vfs { ... }")
+    }
+}
+
 impl Vfs {
-    pub fn new(mut roots: Vec<PathBuf>) -> Vfs {
+    pub fn new(mut roots: Vec<PathBuf>) -> (Vfs, Vec<VfsRoot>) {
         let (worker, worker_handle) = io::start();
 
         let mut res = Vfs {
@@ -142,7 +151,32 @@ impl Vfs {
             };
             res.worker.inp.send(task);
         }
-        res
+        let roots = res.roots.iter().map(|(id, _)| id).collect();
+        (res, roots)
+    }
+
+    pub fn path2file(&self, path: &Path) -> Option<VfsFile> {
+        if let Some((_root, _path, Some(file))) = self.find_root(path) {
+            return Some(file);
+        }
+        None
+    }
+
+    pub fn file2path(&self, file: VfsFile) -> PathBuf {
+        let rel_path = &self.files[file].path;
+        let root_path = &self.roots[self.files[file].root].root;
+        rel_path.to_path(root_path)
+    }
+
+    pub fn file_for_path(&self, path: &Path) -> Option<VfsFile> {
+        if let Some((_root, _path, Some(file))) = self.find_root(path) {
+            return Some(file);
+        }
+        None
+    }
+
+    pub fn load(&mut self, path: &Path) -> Option<VfsFile> {
+        None
     }
 
     pub fn task_receiver(&self) -> &Receiver<io::TaskResult> {
@@ -163,14 +197,17 @@ impl Vfs {
         self.pending_changes.push(change);
     }
 
-    pub fn add_file_overlay(&mut self, path: &Path, text: String) {
+    pub fn add_file_overlay(&mut self, path: &Path, text: String) -> Option<VfsFile> {
+        let mut res = None;
         if let Some((root, path, file)) = self.find_root(path) {
             let text = Arc::new(text);
             let change = if let Some(file) = file {
+                res = Some(file);
                 self.change_file(file, Arc::clone(&text));
                 VfsChange::ChangeFile { file, text }
             } else {
                 let file = self.add_file(root, path.clone(), Arc::clone(&text));
+                res = Some(file);
                 VfsChange::AddFile {
                     file,
                     text,
@@ -180,6 +217,7 @@ impl Vfs {
             };
             self.pending_changes.push(change);
         }
+        res
     }
 
     pub fn change_file_overlay(&mut self, path: &Path, new_text: String) {
@@ -192,9 +230,11 @@ impl Vfs {
         }
     }
 
-    pub fn remove_file_overlay(&mut self, path: &Path) {
+    pub fn remove_file_overlay(&mut self, path: &Path) -> Option<VfsFile> {
+        let mut res = None;
         if let Some((root, path, file)) = self.find_root(path) {
             let file = file.expect("can't remove a file which wasn't added");
+            res = Some(file);
             let full_path = path.to_path(&self.roots[root].root);
             let change = if let Ok(text) = fs::read_to_string(&full_path) {
                 let text = Arc::new(text);
@@ -206,6 +246,7 @@ impl Vfs {
             };
             self.pending_changes.push(change);
         }
+        res
     }
 
     pub fn commit_changes(&mut self) -> Vec<VfsChange> {
diff --git a/crates/thread_worker/src/lib.rs b/crates/thread_worker/src/lib.rs
index 24d7fcce1..12e8bf17e 100644
--- a/crates/thread_worker/src/lib.rs
+++ b/crates/thread_worker/src/lib.rs
@@ -37,6 +37,9 @@ impl<I, O> Worker<I, O> {
     pub fn send(&self, item: I) {
         self.inp.send(item)
     }
+    pub fn recv(&self) -> Option<O> {
+        self.out.recv()
+    }
 }
 
 impl WorkerHandle {