src/third_party/web_platform_tests/streams/readable-streams/tee.js

'use strict';

if (self.importScripts) {
  self.importScripts('../resources/rs-utils.js');
  self.importScripts('/resources/testharness.js');
}

test(() => {

  const rs = new ReadableStream();
  const result = rs.tee();

  assert_true(Array.isArray(result), 'return value should be an array');
  assert_equals(result.length, 2, 'array should have length 2');
  assert_equals(result[0].constructor, ReadableStream, '0th element should be a ReadableStream');
  assert_equals(result[1].constructor, ReadableStream, '1st element should be a ReadableStream');

}, 'ReadableStream teeing: rs.tee() returns an array of two ReadableStreams');

promise_test(t => {

  const rs = new ReadableStream({
    start(c) {
      c.enqueue('a');
      c.enqueue('b');
      c.close();
    }
  });

  const branch = rs.tee();
  const branch1 = branch[0];
  const branch2 = branch[1];
  const reader1 = branch1.getReader();
  const reader2 = branch2.getReader();

  reader2.closed.then(t.unreached_func('branch2 should not be closed'));

  return Promise.all([
    reader1.closed,
    reader1.read().then(r => {
      assert_object_equals(r, { value: 'a', done: false }, 'first chunk from branch1 should be correct');
    }),
    reader1.read().then(r => {
      assert_object_equals(r, { value: 'b', done: false }, 'second chunk from branch1 should be correct');
    }),
    reader1.read().then(r => {
      assert_object_equals(r, { value: undefined, done: true }, 'third read() from branch1 should be done');
    }),
    reader2.read().then(r => {
      assert_object_equals(r, { value: 'a', done: false }, 'first chunk from branch2 should be correct');
    })
  ]);

}, 'ReadableStream teeing: should be able to read one branch to the end without affecting the other');

promise_test(() => {

  const theObject = { the: 'test object' };
  const rs = new ReadableStream({
    start(c) {
      c.enqueue(theObject);
    }
  });

  const branch = rs.tee();
  const branch1 = branch[0];
  const branch2 = branch[1];
  const reader1 = branch1.getReader();
  const reader2 = branch2.getReader();

  return Promise.all([reader1.read(), reader2.read()]).then(values => {
    assert_object_equals(values[0], values[1], 'the values should be equal');
  });

}, 'ReadableStream teeing: values should be equal across each branch');

promise_test(t => {

  const theError = { name: 'boo!' };
  const rs = new ReadableStream({
    start(c) {
      c.enqueue('a');
      c.enqueue('b');
    },
    pull() {
      throw theError;
    }
  });

  const branches = rs.tee();
  const reader1 = branches[0].getReader();
  const reader2 = branches[1].getReader();

  reader1.label = 'reader1';
  reader2.label = 'reader2';

  return Promise.all([
    promise_rejects(t, theError, reader1.closed),
    promise_rejects(t, theError, reader2.closed),
    reader1.read().then(r => {
      assert_object_equals(r, { value: 'a', done: false }, 'should be able to read the first chunk in branch1');
    }),
    reader1.read().then(r => {
      assert_object_equals(r, { value: 'b', done: false }, 'should be able to read the second chunk in branch1');

      return promise_rejects(t, theError, reader2.read());
    })
    .then(() => promise_rejects(t, theError, reader1.read()))
  ]);

}, 'ReadableStream teeing: errors in the source should propagate to both branches');

promise_test(() => {

  const rs = new ReadableStream({
    start(c) {
      c.enqueue('a');
      c.enqueue('b');
      c.close();
    }
  });

  const branches = rs.tee();
  const branch1 = branches[0];
  const branch2 = branches[1];
  branch1.cancel();

  return Promise.all([
    readableStreamToArray(branch1).then(chunks => {
      assert_array_equals(chunks, [], 'branch1 should have no chunks');
    }),
    readableStreamToArray(branch2).then(chunks => {
      assert_array_equals(chunks, ['a', 'b'], 'branch2 should have two chunks');
    })
  ]);

}, 'ReadableStream teeing: canceling branch1 should not impact branch2');

promise_test(() => {

  const rs = new ReadableStream({
    start(c) {
      c.enqueue('a');
      c.enqueue('b');
      c.close();
    }
  });

  const branches = rs.tee();
  const branch1 = branches[0];
  const branch2 = branches[1];
  branch2.cancel();

  return Promise.all([
    readableStreamToArray(branch1).then(chunks => {
      assert_array_equals(chunks, ['a', 'b'], 'branch1 should have two chunks');
    }),
    readableStreamToArray(branch2).then(chunks => {
      assert_array_equals(chunks, [], 'branch2 should have no chunks');
    })
  ]);

}, 'ReadableStream teeing: canceling branch2 should not impact branch2');

promise_test(() => {

  const reason1 = new Error('We\'re wanted men.');
  const reason2 = new Error('I have the death sentence on twelve systems.');

  let resolve;
  const promise = new Promise(r => resolve = r);
  const rs = new ReadableStream({
    cancel(reason) {
      assert_array_equals(reason, [reason1, reason2],
                          'the cancel reason should be an array containing those from the branches');
      resolve();
    }
  });

  const branch = rs.tee();
  const branch1 = branch[0];
  const branch2 = branch[1];
  branch1.cancel(reason1);
  branch2.cancel(reason2);

  return promise;

}, 'ReadableStream teeing: canceling both branches should aggregate the cancel reasons into an array');

promise_test(t => {

  const theError = { name: 'I\'ll be careful.' };
  const rs = new ReadableStream({
    cancel() {
      throw theError;
    }
  });

  const branch = rs.tee();
  const branch1 = branch[0];
  const branch2 = branch[1];

  return Promise.all([
    promise_rejects(t, theError, branch1.cancel()),
    promise_rejects(t, theError, branch2.cancel())
  ]);

}, 'ReadableStream teeing: failing to cancel the original stream should cause cancel() to reject on branches');

promise_test(() => {

  let controller;
  const rs = new ReadableStream({
    start(c) {
      controller = c;
    }
  });

  const branches = rs.tee();
  const reader1 = branches[0].getReader();
  const reader2 = branches[1].getReader();

  const promise = Promise.all([reader1.closed, reader2.closed]);

  controller.close();
  return promise;

}, 'ReadableStream teeing: closing the original should immediately close the branches');

promise_test(t => {

  let controller;
  const rs = new ReadableStream({
    start(c) {
      controller = c;
    }
  });

  const branches = rs.tee();
  const reader1 = branches[0].getReader();
  const reader2 = branches[1].getReader();

  const theError = { name: 'boo!' };
  const promise = Promise.all([
    promise_rejects(t, theError, reader1.closed),
    promise_rejects(t, theError, reader2.closed)
  ]);

  controller.error(theError);
  return promise;

}, 'ReadableStream teeing: erroring the original should immediately error the branches');

done();