Flush all buffered data events on terminal close

Fixes #85257

extensions/vscode-api-tests/src/singlefolder-tests/workspace.tasks.test.ts

@@ -69,7 +69,64 @@ suite('workspace-namespace', () => {
 				},
 				resolveTask(_task: Task): Task | undefined {
 					try {
-					assert.fail('resolveTask should not trigger during the test');
+						assert.fail('resolveTask should not trigger during the test');
+					} catch (e) {
+						done(e);
+					}
+					return undefined;
+				}
+			}));
+			commands.executeCommand('workbench.action.tasks.runTask', `${taskType}: ${taskName}`);
+		});
+
+		test('sync CustomExecution task should flush all data on close', (done) => {
+			interface CustomTestingTaskDefinition extends TaskDefinition {
+				/**
+				 * One of the task properties. This can be used to customize the task in the tasks.json
+				 */
+				customProp1: string;
+			}
+			const taskType: string = 'customTesting';
+			const taskName = 'First custom task';
+			disposables.push(window.onDidOpenTerminal(term => {
+				disposables.push(window.onDidWriteTerminalData(e => {
+					try {
+						assert.equal(e.data, 'exiting');
+					} catch (e) {
+						done(e);
+					}
+					disposables.push(window.onDidCloseTerminal(() => done()));
+					term.dispose();
+				}));
+			}));
+			disposables.push(tasks.registerTaskProvider(taskType, {
+				provideTasks: () => {
+					const result: Task[] = [];
+					const kind: CustomTestingTaskDefinition = {
+						type: taskType,
+						customProp1: 'testing task one'
+					};
+					const writeEmitter = new EventEmitter<string>();
+					const closeEmitter = new EventEmitter<void>();
+					const execution = new CustomExecution((): Thenable<Pseudoterminal> => {
+						const pty: Pseudoterminal = {
+							onDidWrite: writeEmitter.event,
+							onDidClose: closeEmitter.event,
+							open: () => {
+								writeEmitter.fire('exiting');
+								closeEmitter.fire();
+							},
+							close: () => {}
+						};
+						return Promise.resolve(pty);
+					});
+					const task = new Task2(kind, TaskScope.Workspace, taskName, taskType, execution);
+					result.push(task);
+					return result;
+				},
+				resolveTask(_task: Task): Task | undefined {
+					try {
+						assert.fail('resolveTask should not trigger during the test');
 					} catch (e) {
 						done(e);
 					}