Promise.prototype.finally

[leobalter]

@ljharb I guess you already have some tests for this method, right? We want to make a plan to bring these tests as soon as you get the proposal to stage 3.

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• Promise.prototype.finally: add tests #1156

[ljharb]

My intention is to write the PR as soon as I reach stage 3, since it's a stage 4 requirement. However, I won't be seeking that until May or July at a minimum, so there's plenty of time.

[gsathya]

There's a bunch of tests in V8 for this FYI

[gsathya]

Some more tests if someone wants to write up a PR --

var count = 0;
class FooPromise extends Promise {
  constructor(resolve, reject) {
    count++;
    return super(resolve, reject);
  }
}

testAsync(assert => {
  assert.plan(1);
  count = 0;

  new FooPromise(r => r()).finally(() => {}).then(() => {
    assert.equals(6, count);
  });
}, "finally/speciesconstructor");

testAsync(assert => {
  assert.plan(1);
  count = 0;

  FooPromise.resolve().finally(() => {}).then(() => {
    assert.equals(6, count);
  })
}, "resolve/finally/speciesconstructor");

testAsync(assert => {
  assert.plan(1);
  count = 0;

  FooPromise.reject().finally(() => {}).catch(() => {
    assert.equals(6, count);
  })
}, "reject/finally/speciesconstructor");

testAsync(assert => {
  assert.plan(2);

  class MyPromise extends Promise {
    static get [Symbol.species]() { return Promise; }
  }

  var p = Promise
      .resolve()
      .finally(() => MyPromise.resolve());

  assert.equals(true, p instanceof Promise);
  assert.equals(false, p instanceof MyPromise);
}, "finally/Symbol.Species");

[gsathya]

Another test for tc39/proposal-promise-finally@a162888 that's missing:

(function testIsObject() {
  var called = false;
  var p = new Proxy(Promise.resolve(), {});
  var oldThen = Promise.prototype.then;
  Promise.prototype.then = () => called = true;
  Promise.prototype.finally.call(p);
  assertTrue(called);
  Promise.prototype.then = oldThen;
})();

[ljharb]

test262 doesn't seem to have a testAsync helper of any kind.