Fix sporadic misplacement of hover tooltips

Author: yamaton

packages/jupyterlab-lsp/src/features/hover.ts

@@ -46,6 +46,11 @@ interface IResponseData {
   ce_editor: CodeEditor.IEditor;
 }
 
+interface IOnHoverResponse {
+  hover: lsProtocol.Hover;
+  position: IVirtualPosition;
+}
+
 /**
  * Check whether mouse is close to given element (within a specified number of pixels)
  * @param what target element
@@ -127,12 +132,10 @@ export class HoverCM extends CodeMirrorIntegration {
   private virtual_position: IVirtualPosition;
   protected cache: ResponseCache;
 
-  private debounced_get_hover: Throttler<
-    Promise<lsProtocol.Hover | undefined | null>
-  >;
+  private debounced_get_hover: Throttler<Promise<IOnHoverResponse | null>>;
   private tooltip: FreeTooltip;
   private _previousHoverRequest: Promise<
-    Promise<lsProtocol.Hover | undefined | null>
+    Promise<IOnHoverResponse | null>
   > | null = null;
 
   constructor(options: IEditorIntegrationOptions) {
@@ -251,13 +254,10 @@ export class HoverCM extends CodeMirrorIntegration {
   }
 
   protected create_throttler() {
-    return new Throttler<Promise<lsProtocol.Hover | undefined | null>>(
-      this.on_hover,
-      {
-        limit: this.settings.composite.throttlerDelay,
-        edge: 'trailing'
-      }
-    );
+    return new Throttler<Promise<IOnHoverResponse | null>>(this.on_hover, {
+      limit: this.settings.composite.throttlerDelay,
+      edge: 'trailing'
+    });
   }
 
   afterChange(change: IEditorChange, root_position: IRootPosition) {
@@ -268,17 +268,20 @@ export class HoverCM extends CodeMirrorIntegration {
     this.remove_range_highlight();
   }
 
-  protected on_hover = async () => {
+  protected on_hover = async (
+    position: IVirtualPosition
+  ): Promise<IOnHoverResponse | null> => {
     if (
       !(
         this.connection.isReady &&
         this.connection.serverCapabilities?.hoverProvider
       )
     ) {
-      return;
+      return null;
     }
-    let position = this.virtual_position;
-    return await this.connection.clientRequests['textDocument/hover'].request({
+    const hover = await this.connection.clientRequests[
+      'textDocument/hover'
+    ].request({
       textDocument: {
         // this might be wrong - should not it be using the specific virtual document?
         uri: this.virtual_document.document_info.uri
@@ -288,6 +291,15 @@ export class HoverCM extends CodeMirrorIntegration {
         character: position.ch
       }
     });
+
+    if (hover == null) {
+      return null;
+    }
+
+    return {
+      hover: hover,
+      position: position
+    };
   };
 
   protected static get_markup_for_hover(
@@ -442,28 +454,32 @@ export class HoverCM extends CodeMirrorIntegration {
       let response_data = this.restore_from_cache(document, virtual_position);
 
       if (response_data == null) {
-        const promise = this.debounced_get_hover.invoke();
+        const promise = this.debounced_get_hover.invoke(virtual_position);
         this._previousHoverRequest = promise;
         let response = await promise;
         if (this._previousHoverRequest === promise) {
           this._previousHoverRequest = null;
         }
-        if (response && this.is_useful_response(response)) {
+        if (
+          response &&
+          is_equal(response.position, virtual_position) &&
+          this.is_useful_response(response.hover)
+        ) {
           let ce_editor =
             this.virtual_editor.get_editor_at_root_position(root_position);
           let cm_editor =
             this.virtual_editor.ce_editor_to_cm_editor.get(ce_editor)!;
 
           let editor_range = this.get_editor_range(
-            response,
+            response.hover,
             root_position,
             token,
             cm_editor
           );
 
           response_data = {
             response: this.add_range_if_needed(
-              response,
+              response.hover,
               editor_range,
               ce_editor
             ),