Add Signal to proxy all Completer selected Signals (#16312)

* Add Signal to proxy all Completer selected Signals

Completer currently emits a signal when a completion is selected.
This surfaces that signal to the CompletionProviderManager, which
then proxies all the Completer signals to the new signal.

This will allow extensions to know when a selection is made in a
Completer. Currently there are edge cases where a selection can be
made without calling a command that can be connected to.

Signed-off-by: Alex Bozarth <ajbozart@us.ibm.com>

* Emit ICompleterSelection instead of string

* change text to insertText

* add new test for selected

---------

Signed-off-by: Alex Bozarth <ajbozart@us.ibm.com>

packages/completer/src/manager.ts

@@ -10,6 +10,7 @@ import { CompletionHandler } from './handler';
 import { CompleterModel } from './model';
 import { InlineCompleter } from './inline';
 import {
+  ICompleterSelection,
   ICompletionContext,
   ICompletionProvider,
   ICompletionProviderManager,
@@ -36,6 +37,10 @@ export class CompletionProviderManager implements ICompletionProviderManager {
     this._activeProvidersChanged = new Signal<ICompletionProviderManager, void>(
       this
     );
+    this._selected = new Signal<
+      ICompletionProviderManager,
+      ICompleterSelection
+    >(this);
     this._inlineCompleterFactory = null;
   }
 
@@ -46,6 +51,13 @@ export class CompletionProviderManager implements ICompletionProviderManager {
     return this._activeProvidersChanged;
   }
 
+  /**
+   * Signal emitted when a selection is made from a completer menu.
+   */
+  get selected(): ISignal<ICompletionProviderManager, ICompleterSelection> {
+    return this._selected;
+  }
+
   /**
    * Set provider timeout.
    *
@@ -172,6 +184,9 @@ export class CompletionProviderManager implements ICompletionProviderManager {
       // Create a new handler.
       const handler = await this._generateHandler(newCompleterContext, options);
       this._panelHandlers.set(widget.id, handler);
+      handler.completer.selected.connect((completer, insertText) =>
+        this._selected.emit({ insertText })
+      );
       widget.disposed.connect(old => {
         this.disposeHandler(old.id, handler);
         this._mostRecentContext.delete(id);
@@ -410,6 +425,7 @@ export class CompletionProviderManager implements ICompletionProviderManager {
   private _autoCompletion: boolean;
 
   private _activeProvidersChanged: Signal<ICompletionProviderManager, void>;
+  private _selected: Signal<ICompletionProviderManager, ICompleterSelection>;
   private _inlineCompleterFactory: IInlineCompleterFactory | null;
   private _inlineCompleterSettings = InlineCompleter.defaultSettings;
 }

packages/completer/src/tokens.ts

@@ -383,6 +383,11 @@ export interface ICompletionProviderManager {
    */
   activeProvidersChanged: ISignal<ICompletionProviderManager, void>;
 
+  /**
+   * Signal emitted when a selection is made from a completer menu.
+   */
+  selected: ISignal<ICompletionProviderManager, ICompleterSelection>;
+
   /**
    * Inline completer actions.
    */
@@ -394,6 +399,13 @@ export interface ICompletionProviderManager {
   inlineProviders?: IInlineCompletionProviderInfo[];
 }
 
+export interface ICompleterSelection {
+  /**
+   * The text selected by the completer.
+   */
+  insertText: string;
+}
+
 export interface IInlineCompleterActions {
   /**
    * Invoke inline completer.

packages/metapackage/test/completer/manager.spec.ts

@@ -24,6 +24,8 @@ import { createStandaloneCell } from '@jupyter/ydoc';
 
 import { createSessionContext } from '@jupyterlab/apputils/lib/testutils';
 import { NBTestUtils } from '@jupyterlab/notebook/lib/testutils';
+import { MessageLoop } from '@lumino/messaging';
+import { Widget } from '@lumino/widgets';
 
 const DEFAULT_PROVIDER_ID = 'CompletionProvider:context';
 const SAMPLE_PROVIDER_ID = 'CompletionProvider:sample';
@@ -241,5 +243,32 @@ describe('completer/manager', () => {
         expect(handler.completer.model).toBeInstanceOf(CustomCompleterModel);
       });
     });
+
+    describe('#selected', () => {
+      let completerContext: ICompletionContext;
+      let widget: NotebookPanel;
+
+      beforeEach(() => {
+        const context = contextFactory();
+        widget = NBTestUtils.createNotebookPanel(context);
+        completerContext = { widget };
+      });
+
+      it('should emit `selected` signal', async () => {
+        const callback = jest.fn();
+        await manager.updateCompleter(completerContext);
+        const handler = manager['_panelHandlers'].get(
+          widget.id
+        ) as CompletionHandler;
+        handler.completer.model!.setCompletionItems([{ label: 'foo' }]);
+        MessageLoop.sendMessage(handler.completer, Widget.Msg.UpdateRequest);
+
+        manager.selected.connect(callback);
+        expect(callback).toHaveBeenCalledTimes(0);
+        manager.select(widget.id);
+        expect(callback).toHaveBeenCalledTimes(1);
+        manager.selected.disconnect(callback);
+      });
+    });
   });
 });