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async-iterator.any.js
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async-iterator.any.js
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// META: global=worker,jsshell
// META: script=../resources/rs-utils.js
// META: script=../resources/test-utils.js
// META: script=../resources/recording-streams.js
'use strict';
test(() => {
assert_equals(ReadableStream.prototype[Symbol.asyncIterator], ReadableStream.prototype.getIterator);
}, '@@asyncIterator() method is === to getIterator() method');
promise_test(async () => {
const s = new ReadableStream({
start(c) {
c.enqueue(1);
c.enqueue(2);
c.enqueue(3);
c.close();
},
});
const chunks = [];
for await (const chunk of s) {
chunks.push(chunk);
}
assert_array_equals(chunks, [1, 2, 3]);
}, 'Async-iterating a push source');
promise_test(async () => {
let i = 1;
const s = new ReadableStream({
pull(c) {
c.enqueue(i);
if (i >= 3) {
c.close();
}
i += 1;
},
});
const chunks = [];
for await (const chunk of s) {
chunks.push(chunk);
}
assert_array_equals(chunks, [1, 2, 3]);
}, 'Async-iterating a pull source');
promise_test(async () => {
const s = new ReadableStream({
start(c) {
c.error('e');
},
});
try {
for await (const chunk of s) {}
assert_unreached();
} catch (e) {
assert_equals(e, 'e');
}
}, 'Async-iterating an errored stream throws');
promise_test(async () => {
const s = new ReadableStream({
start(c) {
c.close();
}
});
for await (const chunk of s) {
assert_unreached();
}
}, 'Async-iterating a closed stream never executes the loop body, but works fine');
promise_test(async () => {
const s = new ReadableStream();
const loop = async () => {
for await (const chunk of s) {
assert_unreached();
}
assert_unreached();
};
await Promise.race([
loop(),
delay(500)
]);
}, 'Async-iterating an empty but not closed/errored stream never executes the loop body and stalls the async function');
promise_test(async () => {
const s = new ReadableStream({
start(c) {
c.enqueue(1);
c.enqueue(2);
c.enqueue(3);
c.close();
},
});
const reader = s.getReader();
const readResult = await reader.read();
assert_equals(readResult.done, false);
assert_equals(readResult.value, 1);
reader.releaseLock();
const chunks = [];
for await (const chunk of s) {
chunks.push(chunk);
}
assert_array_equals(chunks, [2, 3]);
}, 'Async-iterating a partially consumed stream');
promise_test(async () => {
const test = async (type, preventCancel) => {
const s = recordingReadableStream({
start(c) {
c.enqueue(0);
}
});
// use a separate function for the loop body so return does not stop the test
const loop = async () => {
for await (const c of s.getIterator({ preventCancel })) {
if (type === 'throw') {
throw new Error();
} else if (type === 'break') {
break;
} else if (type === 'return') {
return;
}
}
};
try {
await loop();
} catch (e) {}
if (preventCancel) {
assert_array_equals(s.events, ['pull'], `cancel() should not be called when type = '${type}' and preventCancel is true`);
} else {
assert_array_equals(s.events, ['pull', 'cancel', undefined], `cancel() should be called when type = '${type}' and preventCancel is false`);
}
};
for (const t of ['throw', 'break', 'return']) {
await test(t, true);
await test(t, false);
}
}, 'Cancellation behavior');
promise_test(async () => {
const test = async (preventCancel) => {
const s = recordingReadableStream({
start(c) {
c.enqueue(0);
}
});
const it = s.getIterator({ preventCancel });
await it.return();
if (preventCancel) {
assert_array_equals(s.events, [], `cancel() should not be called when preventCancel is true`);
} else {
assert_array_equals(s.events, ['cancel', undefined], `cancel() should be called when preventCancel is false`);
}
};
await test(true);
await test(false);
}, 'Cancellation behavior when manually calling return()');
promise_test(async () => {
const s = new ReadableStream();
const it = s[Symbol.asyncIterator]();
await it.return();
try {
await it.return();
assert_unreached();
} catch (e) {}
}, 'Calling return() twice rejects');
promise_test(async () => {
const s = new ReadableStream({
start(c) {
c.enqueue(0);
c.close();
},
});
const it = s[Symbol.asyncIterator]();
const next = await it.next();
assert_equals(Object.getPrototypeOf(next), Object.prototype);
assert_array_equals(Object.getOwnPropertyNames(next).sort(), ['done', 'value']);
}, 'next()\'s fulfillment value has the right shape');
promise_test(async t => {
const s = recordingReadableStream();
const it = s[Symbol.asyncIterator]();
it.next();
await promise_rejects(t, new TypeError(), it.return(), 'return() should reject');
assert_array_equals(s.events, ['pull']);
}, 'calling return() while there are pending reads rejects');
test(() => {
const s = new ReadableStream({
start(c) {
c.enqueue(0);
c.close();
},
});
const it = s.getIterator();
assert_throws(new TypeError(), () => s.getIterator(), 'getIterator() should throw');
}, 'getIterator() throws if there\'s already a lock');
promise_test(async () => {
const s = new ReadableStream({
start(c) {
c.enqueue(1);
c.enqueue(2);
c.enqueue(3);
c.close();
},
});
const chunks = [];
for await (const chunk of s) {
chunks.push(chunk);
}
assert_array_equals(chunks, [1, 2, 3]);
const reader = s.getReader();
await reader.closed;
}, 'Acquiring a reader after exhaustively async-iterating a stream');
promise_test(async () => {
const s = new ReadableStream({
start(c) {
c.enqueue(1);
c.enqueue(2);
c.enqueue(3);
c.close();
},
});
// read the first two chunks, then cancel
const chunks = [];
for await (const chunk of s) {
chunks.push(chunk);
if (chunk >= 2) {
break;
}
}
assert_array_equals(chunks, [1, 2]);
const reader = s.getReader();
await reader.closed;
}, 'Acquiring a reader after partially async-iterating a stream');
promise_test(async () => {
const s = new ReadableStream({
start(c) {
c.enqueue(1);
c.enqueue(2);
c.enqueue(3);
c.close();
},
});
// read the first two chunks, then release lock
const chunks = [];
for await (const chunk of s.getIterator({preventCancel: true})) {
chunks.push(chunk);
if (chunk >= 2) {
break;
}
}
assert_array_equals(chunks, [1, 2]);
const reader = s.getReader();
const readResult = await reader.read();
assert_equals(readResult.done, false, 'should not be closed yet');
assert_equals(readResult.value, 3, 'should read remaining chunk');
await reader.closed;
}, 'Acquiring a reader and reading the remaining chunks after partially async-iterating a stream with preventCancel = true');