Merge #2898

2898: Remove RWLock from check watcher. r=matklad a=kiljacken

@matklad mentioned this might be a good idea.

So the general idea is that we don't really need the lock, as we can
just clone the check watcher state when creating a snapshot. We can then
use `Arc::get_mut` to get mutable access to the state from `WorldState`
when needed.

Running with this it seems to improve responsiveness a bit while cargo
is running, but I have no hard numbers to prove it. In any case, a
serialization point less is always better when we're trying to be
responsive.

Co-authored-by: Emil Lauridsen <[email protected]>

3 files changed, 11 insertions, 12 deletions

diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index 7822be2e2..746a8fbe9 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -586,12 +586,14 @@ fn on_notification(
 
 fn on_check_task(
     task: CheckTask,
-    world_state: &WorldState,
+    world_state: &mut WorldState,
     task_sender: &Sender<Task>,
 ) -> Result<()> {
     match task {
         CheckTask::ClearDiagnostics => {
-            let cleared_files = world_state.check_watcher.state.write().clear();
+            let state = Arc::get_mut(&mut world_state.check_watcher.state)
+                .expect("couldn't get check watcher state as mutable");
+            let cleared_files = state.clear();
 
             // Send updated diagnostics for each cleared file
             for url in cleared_files {
@@ -600,11 +602,9 @@ fn on_check_task(
         }
 
         CheckTask::AddDiagnostic(url, diagnostic) => {
-            world_state
-                .check_watcher
-                .state
-                .write()
-                .add_diagnostic_with_fixes(url.clone(), diagnostic);
+            let state = Arc::get_mut(&mut world_state.check_watcher.state)
+                .expect("couldn't get check watcher state as mutable");
+            state.add_diagnostic_with_fixes(url.clone(), diagnostic);
 
             // We manually send a diagnostic update when the watcher asks
             // us to, to avoid the issue of having to change the file to
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 8e43f0575..666f2ee29 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -674,8 +674,7 @@ pub fn handle_code_action(
         res.push(action.into());
     }
 
-    for fix in world.check_watcher.read().fixes_for(&params.text_document.uri).into_iter().flatten()
-    {
+    for fix in world.check_watcher.fixes_for(&params.text_document.uri).into_iter().flatten() {
         let fix_range = fix.location.range.conv_with(&line_index);
         if fix_range.intersection(&range).is_none() {
             continue;
@@ -895,7 +894,7 @@ pub fn publish_diagnostics(
             tags: None,
         })
         .collect();
-    if let Some(check_diags) = world.check_watcher.read().diagnostics_for(&uri) {
+    if let Some(check_diags) = world.check_watcher.diagnostics_for(&uri) {
         diagnostics.extend(check_diags.iter().cloned());
     }
     Ok(req::PublishDiagnosticsParams { uri, diagnostics, version: None })
diff --git a/crates/ra_lsp_server/src/world.rs b/crates/ra_lsp_server/src/world.rs
index e7a0acfc7..3059ef9ec 100644
--- a/crates/ra_lsp_server/src/world.rs
+++ b/crates/ra_lsp_server/src/world.rs
@@ -63,7 +63,7 @@ pub struct WorldSnapshot {
     pub workspaces: Arc<Vec<ProjectWorkspace>>,
     pub analysis: Analysis,
     pub latest_requests: Arc<RwLock<LatestRequests>>,
-    pub check_watcher: Arc<RwLock<CheckState>>,
+    pub check_watcher: CheckState,
     vfs: Arc<RwLock<Vfs>>,
 }
 
@@ -220,7 +220,7 @@ impl WorldState {
             analysis: self.analysis_host.analysis(),
             vfs: Arc::clone(&self.vfs),
             latest_requests: Arc::clone(&self.latest_requests),
-            check_watcher: self.check_watcher.state.clone(),
+            check_watcher: (*self.check_watcher.state).clone(),
         }
     }