Auto merge of rust-lang#17248 - mladedav:dm/delay-clear, r=Veykril

Clear diagnostics only after new ones were received

Closes rust-lang#15934

This adds a flag inside the global state which controls when old diagnostics are cleared. Now, old diagnostics should be cleared only after at least one new diagnostic is available.

src/tools/rust-analyzer/crates/rust-analyzer/src/global_state.rs

@@ -87,6 +87,7 @@ pub(crate) struct GlobalState {
     pub(crate) flycheck_sender: Sender<flycheck::Message>,
     pub(crate) flycheck_receiver: Receiver<flycheck::Message>,
     pub(crate) last_flycheck_error: Option<String>,
+    pub(crate) diagnostics_received: bool,
 
     // Test explorer
     pub(crate) test_run_session: Option<Vec<flycheck::CargoTestHandle>>,
@@ -224,6 +225,7 @@ impl GlobalState {
             flycheck_sender,
             flycheck_receiver,
             last_flycheck_error: None,
+            diagnostics_received: false,
 
             test_run_session: None,
             test_run_sender,

src/tools/rust-analyzer/crates/rust-analyzer/src/main_loop.rs

@@ -804,6 +804,10 @@ impl GlobalState {
     fn handle_flycheck_msg(&mut self, message: flycheck::Message) {
         match message {
             flycheck::Message::AddDiagnostic { id, workspace_root, diagnostic } => {
+                if !self.diagnostics_received {
+                    self.diagnostics.clear_check(id);
+                    self.diagnostics_received = true;
+                }
                 let snap = self.snapshot();
                 let diagnostics = crate::diagnostics::to_proto::map_rust_diagnostic_to_lsp(
                     &self.config.diagnostics_map(),
@@ -832,7 +836,7 @@ impl GlobalState {
             flycheck::Message::Progress { id, progress } => {
                 let (state, message) = match progress {
                     flycheck::Progress::DidStart => {
-                        self.diagnostics.clear_check(id);
+                        self.diagnostics_received = false;
                         (Progress::Begin, None)
                     }
                     flycheck::Progress::DidCheckCrate(target) => (Progress::Report, Some(target)),
@@ -848,6 +852,9 @@ impl GlobalState {
                     flycheck::Progress::DidFinish(result) => {
                         self.last_flycheck_error =
                             result.err().map(|err| format!("cargo check failed to start: {err}"));
+                        if !self.diagnostics_received {
+                            self.diagnostics.clear_check(id);
+                        }
                         (Progress::End, None)
                     }
                 };