streams/transform-streams/general.any.js

// META: global=window,worker
// META: script=../resources/test-utils.js
// META: script=../resources/rs-utils.js
'use strict';

test(() => {
  new TransformStream({ transform() { } });
}, 'TransformStream can be constructed with a transform function');

test(() => {
  new TransformStream();
  new TransformStream({});
}, 'TransformStream can be constructed with no transform function');

test(() => {
  const ts = new TransformStream({ transform() { } });

  const writer = ts.writable.getWriter();
  assert_equals(writer.desiredSize, 1, 'writer.desiredSize should be 1');
}, 'TransformStream writable starts in the writable state');

promise_test(() => {
  const ts = new TransformStream();

  const writer = ts.writable.getWriter();
  writer.write('a');
  assert_equals(writer.desiredSize, 0, 'writer.desiredSize should be 0 after write()');

  return ts.readable.getReader().read().then(result => {
    assert_equals(result.value, 'a',
      'result from reading the readable is the same as was written to writable');
    assert_false(result.done, 'stream should not be done');

    return delay(0).then(() => assert_equals(writer.desiredSize, 1, 'desiredSize should be 1 again'));
  });
}, 'Identity TransformStream: can read from readable what is put into writable');

promise_test(() => {
  let c;
  const ts = new TransformStream({
    start(controller) {
      c = controller;
    },
    transform(chunk) {
      c.enqueue(chunk.toUpperCase());
    }
  });

  const writer = ts.writable.getWriter();
  writer.write('a');

  return ts.readable.getReader().read().then(result => {
    assert_equals(result.value, 'A',
      'result from reading the readable is the transformation of what was written to writable');
    assert_false(result.done, 'stream should not be done');
  });
}, 'Uppercaser sync TransformStream: can read from readable transformed version of what is put into writable');

promise_test(() => {
  let c;
  const ts = new TransformStream({
    start(controller) {
      c = controller;
    },
    transform(chunk) {
      c.enqueue(chunk.toUpperCase());
      c.enqueue(chunk.toUpperCase());
    }
  });

  const writer = ts.writable.getWriter();
  writer.write('a');

  const reader = ts.readable.getReader();

  return reader.read().then(result1 => {
    assert_equals(result1.value, 'A',
      'the first chunk read is the transformation of the single chunk written');
    assert_false(result1.done, 'stream should not be done');

    return reader.read().then(result2 => {
      assert_equals(result2.value, 'A',
        'the second chunk read is also the transformation of the single chunk written');
      assert_false(result2.done, 'stream should not be done');
    });
  });
}, 'Uppercaser-doubler sync TransformStream: can read both chunks put into the readable');

promise_test(() => {
  let c;
  const ts = new TransformStream({
    start(controller) {
      c = controller;
    },
    transform(chunk) {
      return delay(0).then(() => c.enqueue(chunk.toUpperCase()));
    }
  });

  const writer = ts.writable.getWriter();
  writer.write('a');

  return ts.readable.getReader().read().then(result => {
    assert_equals(result.value, 'A',
      'result from reading the readable is the transformation of what was written to writable');
    assert_false(result.done, 'stream should not be done');
  });
}, 'Uppercaser async TransformStream: can read from readable transformed version of what is put into writable');

promise_test(() => {
  let doSecondEnqueue;
  let returnFromTransform;
  const ts = new TransformStream({
    transform(chunk, controller) {
      delay(0).then(() => controller.enqueue(chunk.toUpperCase()));
      doSecondEnqueue = () => controller.enqueue(chunk.toUpperCase());
      return new Promise(resolve => {
        returnFromTransform = resolve;
      });
    }
  });

  const reader = ts.readable.getReader();

  const writer = ts.writable.getWriter();
  writer.write('a');

  return reader.read().then(result1 => {
    assert_equals(result1.value, 'A',
      'the first chunk read is the transformation of the single chunk written');
    assert_false(result1.done, 'stream should not be done');
    doSecondEnqueue();

    return reader.read().then(result2 => {
      assert_equals(result2.value, 'A',
        'the second chunk read is also the transformation of the single chunk written');
      assert_false(result2.done, 'stream should not be done');
      returnFromTransform();
    });
  });
}, 'Uppercaser-doubler async TransformStream: can read both chunks put into the readable');

promise_test(() => {
  const ts = new TransformStream({ transform() { } });

  const writer = ts.writable.getWriter();
  writer.close();

  return Promise.all([writer.closed, ts.readable.getReader().closed]);
}, 'TransformStream: by default, closing the writable closes the readable (when there are no queued writes)');

promise_test(() => {
  let transformResolve;
  const transformPromise = new Promise(resolve => {
    transformResolve = resolve;
  });
  const ts = new TransformStream({
    transform() {
      return transformPromise;
    }
  }, undefined, { highWaterMark: 1 });

  const writer = ts.writable.getWriter();
  writer.write('a');
  writer.close();

  let rsClosed = false;
  ts.readable.getReader().closed.then(() => {
    rsClosed = true;
  });

  return delay(0).then(() => {
    assert_equals(rsClosed, false, 'readable is not closed after a tick');
    transformResolve();

    return writer.closed.then(() => {
      // TODO: Is this expectation correct?
      assert_equals(rsClosed, true, 'readable is closed at that point');
    });
  });
}, 'TransformStream: by default, closing the writable waits for transforms to finish before closing both');

promise_test(() => {
  let c;
  const ts = new TransformStream({
    start(controller) {
      c = controller;
    },
    transform() {
      c.enqueue('x');
      c.enqueue('y');
      return delay(0);
    }
  });

  const writer = ts.writable.getWriter();
  writer.write('a');
  writer.close();

  const readableChunks = readableStreamToArray(ts.readable);

  return writer.closed.then(() => {
    return readableChunks.then(chunks => {
      assert_array_equals(chunks, ['x', 'y'], 'both enqueued chunks can be read from the readable');
    });
  });
}, 'TransformStream: by default, closing the writable closes the readable after sync enqueues and async done');

promise_test(() => {
  let c;
  const ts = new TransformStream({
    start(controller) {
      c = controller;
    },
    transform() {
      return delay(0)
          .then(() => c.enqueue('x'))
          .then(() => c.enqueue('y'))
          .then(() => delay(0));
    }
  });

  const writer = ts.writable.getWriter();
  writer.write('a');
  writer.close();

  const readableChunks = readableStreamToArray(ts.readable);

  return writer.closed.then(() => {
    return readableChunks.then(chunks => {
      assert_array_equals(chunks, ['x', 'y'], 'both enqueued chunks can be read from the readable');
    });
  });
}, 'TransformStream: by default, closing the writable closes the readable after async enqueues and async done');

promise_test(() => {
  let c;
  const ts = new TransformStream({
    suffix: '-suffix',

    start(controller) {
      c = controller;
      c.enqueue('start' + this.suffix);
    },

    transform(chunk) {
      c.enqueue(chunk + this.suffix);
    },

    flush() {
      c.enqueue('flushed' + this.suffix);
    }
  });

  const writer = ts.writable.getWriter();
  writer.write('a');
  writer.close();

  const readableChunks = readableStreamToArray(ts.readable);

  return writer.closed.then(() => {
    return readableChunks.then(chunks => {
      assert_array_equals(chunks, ['start-suffix', 'a-suffix', 'flushed-suffix'], 'all enqueued chunks have suffixes');
    });
  });
}, 'Transform stream should call transformer methods as methods');

promise_test(() => {
  function functionWithOverloads() {}
  functionWithOverloads.apply = () => assert_unreached('apply() should not be called');
  functionWithOverloads.call = () => assert_unreached('call() should not be called');
  const ts = new TransformStream({
    start: functionWithOverloads,
    transform: functionWithOverloads,
    flush: functionWithOverloads
  });
  const writer = ts.writable.getWriter();
  writer.write('a');
  writer.close();

  return readableStreamToArray(ts.readable);
}, 'methods should not not have .apply() or .call() called');

promise_test(t => {
  let startCalled = false;
  let startDone = false;
  let transformDone = false;
  let flushDone = false;
  const ts = new TransformStream({
    start() {
      startCalled = true;
      return flushAsyncEvents().then(() => {
        startDone = true;
      });
    },
    transform() {
      return t.step(() => {
        assert_true(startDone, 'transform() should not be called until the promise returned from start() has resolved');
        return flushAsyncEvents().then(() => {
          transformDone = true;
        });
      });
    },
    flush() {
      return t.step(() => {
        assert_true(transformDone,
                    'flush() should not be called until the promise returned from transform() has resolved');
        return flushAsyncEvents().then(() => {
          flushDone = true;
        });
      });
    }
  }, undefined, { highWaterMark: 1 });

  assert_true(startCalled, 'start() should be called synchronously');

  const writer = ts.writable.getWriter();
  const writePromise = writer.write('a');
  return writer.close().then(() => {
    assert_true(flushDone, 'promise returned from flush() should have resolved');
    return writePromise;
  });
}, 'TransformStream start, transform, and flush should be strictly ordered');

promise_test(() => {
  let transformCalled = false;
  const ts = new TransformStream({
    transform() {
      transformCalled = true;
    }
  }, undefined, { highWaterMark: Infinity });
  // transform() is only called synchronously when there is no backpressure and all microtasks have run.
  return delay(0).then(() => {
    const writePromise = ts.writable.getWriter().write();
    assert_true(transformCalled, 'transform() should have been called');
    return writePromise;
  });
}, 'it should be possible to call transform() synchronously');

promise_test(() => {
  const ts = new TransformStream({}, undefined, { highWaterMark: 0 });

  const writer = ts.writable.getWriter();
  writer.close();

  return Promise.all([writer.closed, ts.readable.getReader().closed]);
}, 'closing the writable should close the readable when there are no queued chunks, even with backpressure');

test(() => {
  new TransformStream({
    start(controller) {
      controller.terminate();
      assert_throws_js(TypeError, () => controller.enqueue(), 'enqueue should throw');
    }
  });
}, 'enqueue() should throw after controller.terminate()');

promise_test(() => {
  let controller;
  const ts = new TransformStream({
    start(c) {
      controller = c;
    }
  });
  const cancelPromise = ts.readable.cancel();
  assert_throws_js(TypeError, () => controller.enqueue(), 'enqueue should throw');
  return cancelPromise;
}, 'enqueue() should throw after readable.cancel()');

test(() => {
  new TransformStream({
    start(controller) {
      controller.terminate();
      controller.terminate();
    }
  });
}, 'controller.terminate() should do nothing the second time it is called');

promise_test(t => {
  let controller;
  const ts = new TransformStream({
    start(c) {
      controller = c;
    }
  });
  const cancelReason = { name: 'cancelReason' };
  const cancelPromise = ts.readable.cancel(cancelReason);
  controller.terminate();
  return Promise.all([
    cancelPromise,
    promise_rejects_exactly(t, cancelReason, ts.writable.getWriter().closed, 'closed should reject with cancelReason')
  ]);
}, 'terminate() should do nothing after readable.cancel()');

promise_test(() => {
  let calls = 0;
  new TransformStream({
    start() {
      ++calls;
    }
  });
  return flushAsyncEvents().then(() => {
    assert_equals(calls, 1, 'start() should have been called exactly once');
  });
}, 'start() should not be called twice');

test(() => {
  assert_throws_js(RangeError, () => new TransformStream({ readableType: 'bytes' }), 'constructor should throw');
}, 'specifying a defined readableType should throw');

test(() => {
  assert_throws_js(RangeError, () => new TransformStream({ writableType: 'bytes' }), 'constructor should throw');
}, 'specifying a defined writableType should throw');

test(() => {
  class Subclass extends TransformStream {
    extraFunction() {
      return true;
    }
  }
  assert_equals(
      Object.getPrototypeOf(Subclass.prototype), TransformStream.prototype,
      'Subclass.prototype\'s prototype should be TransformStream.prototype');
  assert_equals(Object.getPrototypeOf(Subclass), TransformStream,
                'Subclass\'s prototype should be TransformStream');
  const sub = new Subclass();
  assert_true(sub instanceof TransformStream,
              'Subclass object should be an instance of TransformStream');
  assert_true(sub instanceof Subclass,
              'Subclass object should be an instance of Subclass');
  const readableGetter = Object.getOwnPropertyDescriptor(
      TransformStream.prototype, 'readable').get;
  assert_equals(readableGetter.call(sub), sub.readable,
                'Subclass object should pass brand check');
  assert_true(sub.extraFunction(),
              'extraFunction() should be present on Subclass object');
}, 'Subclassing TransformStream should work');