Update display map snapshots when diagnostics are updated

This is similar to what we do when we receive new parse trees from
tree-sitter.

crates/editor/src/display_map/fold_map.rs

@@ -204,6 +204,7 @@ pub struct FoldMap {
 struct SyncState {
     version: clock::Global,
     parse_count: usize,
+    diagnostics_update_count: usize,
 }
 
 impl FoldMap {
@@ -225,6 +226,7 @@ impl FoldMap {
             last_sync: Mutex::new(SyncState {
                 version: buffer.version(),
                 parse_count: buffer.parse_count(),
+                diagnostics_update_count: buffer.diagnostics_update_count(),
             }),
             version: AtomicUsize::new(0),
         };
@@ -256,6 +258,7 @@ impl FoldMap {
             SyncState {
                 version: buffer.version(),
                 parse_count: buffer.parse_count(),
+                diagnostics_update_count: buffer.diagnostics_update_count(),
             },
         );
         let edits = buffer
@@ -263,7 +266,9 @@ impl FoldMap {
             .map(Into::into)
             .collect::<Vec<_>>();
         if edits.is_empty() {
-            if last_sync.parse_count != buffer.parse_count() {
+            if last_sync.parse_count != buffer.parse_count()
+                || last_sync.diagnostics_update_count != buffer.diagnostics_update_count()
+            {
                 self.version.fetch_add(1, SeqCst);
             }
             Vec::new()

crates/language/src/lib.rs

@@ -63,6 +63,7 @@ pub struct Buffer {
     parsing_in_background: bool,
     parse_count: usize,
     diagnostics: AnchorRangeMultimap<(DiagnosticSeverity, String)>,
+    diagnostics_update_count: usize,
     language_server: Option<LanguageServerState>,
     #[cfg(test)]
     operations: Vec<Operation>,
@@ -288,6 +289,7 @@ impl Buffer {
             pending_autoindent: Default::default(),
             language: None,
             diagnostics: Default::default(),
+            diagnostics_update_count: 0,
             language_server: None,
             #[cfg(test)]
             operations: Default::default(),
@@ -686,6 +688,7 @@ impl Buffer {
             }
         }
 
+        self.diagnostics_update_count += 1;
         cx.notify();
         Ok(())
     }
@@ -705,6 +708,10 @@ impl Buffer {
             })
     }
 
+    pub fn diagnostics_update_count(&self) -> usize {
+        self.diagnostics_update_count
+    }
+
     fn request_autoindent(&mut self, cx: &mut ModelContext<Self>) {
         if let Some(indent_columns) = self.compute_autoindents() {
             let indent_columns = cx.background().spawn(indent_columns);
@@ -1335,6 +1342,7 @@ impl Clone for Buffer {
             autoindent_requests: Default::default(),
             pending_autoindent: Default::default(),
             diagnostics: self.diagnostics.clone(),
+            diagnostics_update_count: self.diagnostics_update_count,
             language_server: None,
             #[cfg(test)]
             operations: self.operations.clone(),