Add button to show outline in Positron Notebook Editor action bar

src/vs/workbench/contrib/positronNotebook/browser/positronNotebook.contribution.ts

@@ -56,7 +56,7 @@ import { POSITRON_EXECUTE_CELL_COMMAND_ID, POSITRON_NOTEBOOK_EDITOR_ID, POSITRON
 import { getActiveCell, getSelectedCells, SelectionState } from './selectionMachine.js';
 import { POSITRON_NOTEBOOK_CELL_CONTEXT_KEYS as CELL_CONTEXT_KEYS, POSITRON_NOTEBOOK_CELL_EDITOR_FOCUSED, POSITRON_NOTEBOOK_EDITOR_FOCUSED, POSITRON_NOTEBOOK_CELL_HAS_OUTPUTS, POSITRON_NOTEBOOK_CELL_JSON_OUTPUT_COUNT, POSITRON_NOTEBOOK_CELL_IMAGE_OUTPUT_COUNT, POSITRON_NOTEBOOK_CELL_OUTPUT_COLLAPSED, POSITRON_NOTEBOOK_CELL_OUTPUT_OVERFLOWS, POSITRON_NOTEBOOK_CELL_OUTPUT_SCROLLING, POSITRON_NOTEBOOK_EXPERIMENTAL, POSITRON_NOTEBOOK_OUTPUT_IMAGE_TARGETED, POSITRON_NOTEBOOK_OUTPUT_JSON_TARGETED } from './ContextKeysManager.js';
 import './contrib/undoRedo/positronNotebookUndoRedo.js';
-import { registerAction2, MenuId, MenuRegistry } from '../../../../platform/actions/common/actions.js';
+import { Action2, registerAction2, MenuId, MenuRegistry } from '../../../../platform/actions/common/actions.js';
 import { ExecuteSelectionInConsoleAction } from './ExecuteSelectionInConsoleAction.js';
 import { ThemeIcon } from '../../../../base/common/themables.js';
 import { KernelStatusBadge } from './KernelStatusBadge.js';
@@ -76,6 +76,8 @@ import './AskAssistantAction.js'; // Register AskAssistantAction
 import { CONTEXT_FIND_INPUT_FOCUSED, CONTEXT_REPLACE_INPUT_FOCUSED } from '../../../../editor/contrib/find/browser/findModel.js';
 import { Codicon } from '../../../../base/common/codicons.js';
 import { EditorContextKeys } from '../../../../editor/common/editorContextKeys.js';
+import { IViewsService } from '../../../services/views/common/viewsService.js';
+import { IOutlinePane } from '../../outline/browser/outline.js';
 
 export const POSITRON_NOTEBOOK_COMMAND_MODE = ContextKeyExpr.and(
 	POSITRON_NOTEBOOK_EDITOR_FOCUSED,
@@ -2103,6 +2105,39 @@ registerAction2(class extends NotebookAction2 {
 	}
 });
 
+// Toggle Outline - Reveals or hides the Outline view in the Explorer pane
+export class ToggleOutlineAction extends Action2 {
+	constructor() {
+		super({
+			id: 'positronNotebook.toggleOutline',
+			title: localize2('toggleOutline', 'Toggle Outline'),
+			icon: ThemeIcon.fromId('list-unordered'),
+			f1: true,
+			category: POSITRON_NOTEBOOK_CATEGORY,
+			positronActionBarOptions: {
+				controlType: 'button',
+				displayTitle: false
+			},
+			menu: {
+				id: MenuId.EditorActionsLeft,
+				group: 'navigation',
+				order: 45,
+				when: ContextKeyExpr.equals('activeEditor', POSITRON_NOTEBOOK_EDITOR_ID)
+			}
+		});
+	}
+
+	override async run(accessor: ServicesAccessor): Promise<void> {
+		const viewsService = accessor.get(IViewsService);
+		if (viewsService.isViewVisible(IOutlinePane.Id)) {
+			viewsService.closeView(IOutlinePane.Id);
+		} else {
+			await viewsService.openView(IOutlinePane.Id, true);
+		}
+	}
+}
+registerAction2(ToggleOutlineAction);
+
 // Ask Assistant - Opens assistant chat with prompt options for the notebook
 // Action is defined in AskAssistantAction.ts
 

src/vs/workbench/contrib/positronNotebook/test/browser/toggleOutlineAction.vitest.ts

@@ -0,0 +1,59 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (C) 2026 Posit Software, PBC. All rights reserved.
+ *  Licensed under the Elastic License 2.0. See LICENSE.txt for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+/// <reference types="vitest/globals" />
+
+import { createTestContainer } from '../../../../../test/vitest/positronTestContainer.js';
+import { stubInterface } from '../../../../../test/vitest/stubInterface.js';
+import { ToggleOutlineAction } from '../../browser/positronNotebook.contribution.js';
+import { IOutlinePane } from '../../../outline/browser/outline.js';
+import { IViewsService } from '../../../../services/views/common/viewsService.js';
+
+describe('ToggleOutlineAction', () => {
+	const ctx = createTestContainer()
+		.withWorkbenchServices()
+		.build();
+
+	let isViewVisible: ReturnType<typeof vi.fn<IViewsService['isViewVisible']>>;
+	// openView is generic (<T extends IView>); store it with a wider mock signature and
+	// re-narrow inside the stub via a closure so stubInterface's Partial<IViewsService>
+	// stays type-correct.
+	let openView: ReturnType<typeof vi.fn<(id: string, focus?: boolean) => Promise<unknown>>>;
+	let closeView: ReturnType<typeof vi.fn<IViewsService['closeView']>>;
+
+	beforeEach(() => {
+		isViewVisible = vi.fn();
+		openView = vi.fn<(id: string, focus?: boolean) => Promise<unknown>>().mockResolvedValue(null);
+		closeView = vi.fn();
+		ctx.instantiationService.stub(IViewsService, stubInterface<IViewsService>({
+			isViewVisible,
+			openView: <T>(id: string, focus?: boolean) => openView(id, focus) as Promise<T | null>,
+			closeView,
+		}));
+	});
+
+	async function run(): Promise<void> {
+		const action = new ToggleOutlineAction();
+		await ctx.instantiationService.invokeFunction(accessor => action.run(accessor));
+	}
+
+	it('opens and focuses the outline view when it is not visible', async () => {
+		isViewVisible.mockReturnValue(false);
+
+		await run();
+
+		expect(openView).toHaveBeenCalledWith(IOutlinePane.Id, true);
+		expect(closeView).not.toHaveBeenCalled();
+	});
+
+	it('closes the outline view when it is visible', async () => {
+		isViewVisible.mockReturnValue(true);
+
+		await run();
+
+		expect(closeView).toHaveBeenCalledWith(IOutlinePane.Id);
+		expect(openView).not.toHaveBeenCalled();
+	});
+});