Clear old diagnostics when restarting a language server

crates/language/src/buffer.rs

@@ -1644,10 +1644,17 @@ impl Buffer {
         cx: &mut ModelContext<Self>,
     ) {
         if lamport_timestamp > self.diagnostics_timestamp {
-            match self.diagnostics.binary_search_by_key(&server_id, |e| e.0) {
-                Err(ix) => self.diagnostics.insert(ix, (server_id, diagnostics)),
-                Ok(ix) => self.diagnostics[ix].1 = diagnostics,
-            };
+            let ix = self.diagnostics.binary_search_by_key(&server_id, |e| e.0);
+            if diagnostics.len() == 0 {
+                if let Ok(ix) = ix {
+                    self.diagnostics.remove(ix);
+                }
+            } else {
+                match ix {
+                    Err(ix) => self.diagnostics.insert(ix, (server_id, diagnostics)),
+                    Ok(ix) => self.diagnostics[ix].1 = diagnostics,
+                };
+            }
             self.diagnostics_timestamp = lamport_timestamp;
             self.diagnostics_update_count += 1;
             self.text.lamport_clock.observe(lamport_timestamp);