Merge from vscode 4c9161a3f125f5a788aafa73a4ecfcb27dcfc319 (#9143)

* Merge from vscode 4c9161a3f125f5a788aafa73a4ecfcb27dcfc319

* minor spacing fix

src/vs/base/test/common/async.test.ts

@@ -557,4 +557,93 @@ suite('Async', () => {
 			assert.equal(error, error);
 		}
 	});
+
+	test('TaskSequentializer - pending basics', async function () {
+		const sequentializer = new async.TaskSequentializer();
+
+		assert.ok(!sequentializer.hasPending());
+		assert.ok(!sequentializer.hasPending(2323));
+		assert.ok(!sequentializer.pending);
+
+		// pending removes itself after done
+		await sequentializer.setPending(1, Promise.resolve());
+		assert.ok(!sequentializer.hasPending());
+		assert.ok(!sequentializer.hasPending(1));
+		assert.ok(!sequentializer.pending);
+
+		// pending removes itself after done (use async.timeout)
+		sequentializer.setPending(2, async.timeout(1));
+		assert.ok(sequentializer.hasPending());
+		assert.ok(sequentializer.hasPending(2));
+		assert.ok(!sequentializer.hasPending(1));
+		assert.ok(sequentializer.pending);
+
+		await async.timeout(2);
+		assert.ok(!sequentializer.hasPending());
+		assert.ok(!sequentializer.hasPending(2));
+		assert.ok(!sequentializer.pending);
+	});
+
+	test('TaskSequentializer - pending and next (finishes instantly)', async function () {
+		const sequentializer = new async.TaskSequentializer();
+
+		let pendingDone = false;
+		sequentializer.setPending(1, async.timeout(1).then(() => { pendingDone = true; return; }));
+
+		// next finishes instantly
+		let nextDone = false;
+		const res = sequentializer.setNext(() => Promise.resolve(null).then(() => { nextDone = true; return; }));
+
+		await res;
+		assert.ok(pendingDone);
+		assert.ok(nextDone);
+	});
+
+	test('TaskSequentializer - pending and next (finishes after timeout)', async function () {
+		const sequentializer = new async.TaskSequentializer();
+
+		let pendingDone = false;
+		sequentializer.setPending(1, async.timeout(1).then(() => { pendingDone = true; return; }));
+
+		// next finishes after async.timeout
+		let nextDone = false;
+		const res = sequentializer.setNext(() => async.timeout(1).then(() => { nextDone = true; return; }));
+
+		await res;
+		assert.ok(pendingDone);
+		assert.ok(nextDone);
+	});
+
+	test('TaskSequentializer - pending and multiple next (last one wins)', async function () {
+		const sequentializer = new async.TaskSequentializer();
+
+		let pendingDone = false;
+		sequentializer.setPending(1, async.timeout(1).then(() => { pendingDone = true; return; }));
+
+		// next finishes after async.timeout
+		let firstDone = false;
+		let firstRes = sequentializer.setNext(() => async.timeout(2).then(() => { firstDone = true; return; }));
+
+		let secondDone = false;
+		let secondRes = sequentializer.setNext(() => async.timeout(3).then(() => { secondDone = true; return; }));
+
+		let thirdDone = false;
+		let thirdRes = sequentializer.setNext(() => async.timeout(4).then(() => { thirdDone = true; return; }));
+
+		await Promise.all([firstRes, secondRes, thirdRes]);
+		assert.ok(pendingDone);
+		assert.ok(!firstDone);
+		assert.ok(!secondDone);
+		assert.ok(thirdDone);
+	});
+
+	test('TaskSequentializer - cancel pending', async function () {
+		const sequentializer = new async.TaskSequentializer();
+
+		let pendingCancelled = false;
+		sequentializer.setPending(1, async.timeout(1), () => pendingCancelled = true);
+		sequentializer.cancelPending();
+
+		assert.ok(pendingCancelled);
+	});
 });