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[WIP] ReadableStream @@asyncIterator tests #13362

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[WIP] ReadableStream @@asyncIterator tests #13362

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929b258
ReadableStream @@asyncIterator tests
devsnek Oct 4, 2018
f890858
Add tests for ReadableStreamAsyncIteratorPrototype brand checks
ricea Oct 5, 2018
64c54b6
squash! some fixes
devsnek Oct 7, 2018
6b1fb12
squash! more fixes
devsnek Oct 7, 2018
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11 changes: 11 additions & 0 deletions streams/readable-streams/async-iterator.html
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
<!DOCTYPE html>
<meta charset="utf-8">
<title>async-iterator.js browser context wrapper file</title>

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<script src="../resources/rs-utils.js"></script>
<script src="../resources/recording-streams.js"></script>

<script src="async-iterator.js"></script>
150 changes: 150 additions & 0 deletions streams/readable-streams/async-iterator.js
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@@ -0,0 +1,150 @@
'use strict';

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

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 iterator 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 iterator 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 () => {

}, 'Async-iterating an empty but not closed/errored stream never executes the loop body and stalls the async function');

promise_test(async () => {
const test = async (type, preventCancel) => {
const s = recordingReadableStream({
start(c) {
c.enqueue(0);
}
});

await (async () => {
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I find this immediately-executed-async-function structure hard to understand. Is there a reason why a simple try ... catch wouldn't work?

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testing return. I suppose it can be reworked a little bit though.

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Probably if you just split the creation of the function from the execution of the function it will be enough to make it less confusing.

for await (const c of s.getIterator({ preventCancel })) {
if (type === 'throw') {
throw new Error();
} else if (type === 'break') {
break;
} else if (type === 'return') {
return;
}
}
})().catch(() => 0);

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 s = new ReadableStream();
const it = s[Symbol.asyncIterator]();
await it.return();
try {
await it.return();
assert_unreached();
} catch (e) {}
}

{
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.keys(next), ['value', 'done']);
}
}, 'manual manipulation');

test(() => {
const s = new ReadableStream({
start(c) {
c.enqueue(0);
c.close();
},
});
const it = s.getIterator();
try {
s.getIterator();
assert_unreached();
} catch (e) {}
}, 'getIterator throws if there\'s already a lock');
29 changes: 29 additions & 0 deletions streams/readable-streams/brand-checks.js
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Expand Up @@ -7,6 +7,7 @@ if (self.importScripts) {

let ReadableStreamDefaultReader;
let ReadableStreamDefaultController;
let ReadableStreamAsyncIteratorPrototype;

test(() => {

Expand All @@ -26,6 +27,13 @@ test(() => {

}, 'Can get the ReadableStreamDefaultController constructor indirectly');

test(() => {

const rs = new ReadableStream();
ReadableStreamAsyncIteratorPrototype = Object.getPrototypeOf(rs.getIterator());

}, 'Can get ReadableStreamAsyncIteratorPrototype object indirectly');

function fakeRS() {
return Object.setPrototypeOf({
cancel() { return Promise.resolve(); },
Expand Down Expand Up @@ -71,6 +79,13 @@ function realRSDefaultController() {
return controller;
}

function fakeRSAsyncIterator() {
return Object.setPrototypeOf({
next() { },
return(value = undefined) { }
}, ReadableStreamAsyncIteratorPrototype);
}

promise_test(t => {

return methodRejectsForAll(t, ReadableStream.prototype, 'cancel',
Expand Down Expand Up @@ -161,4 +176,18 @@ test(() => {

}, 'ReadableStreamDefaultController.prototype.error enforces a brand check');

promise_test(t => {

return methodRejectsForAll(t, ReadableStreamAsyncIteratorPrototype, 'next',
[fakeRSAsyncIterator(), realRS(), realRSDefaultReader(), undefined, null]);

}, 'ReadableStreamAsyncIteratorPrototype.next enforces a brand check');

promise_test(t => {

return methodRejectsForAll(t, ReadableStreamAsyncIteratorPrototype, 'return',
[fakeRSAsyncIterator(), realRS(), realRSDefaultReader(), undefined, null]);

}, 'ReadableStreamAsyncIteratorPrototype.return enforces a brand check');

done();
3 changes: 2 additions & 1 deletion streams/readable-streams/general.js
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Expand Up @@ -42,7 +42,7 @@ test(() => {

test(() => {

const methods = ['cancel', 'constructor', 'getReader', 'pipeThrough', 'pipeTo', 'tee'];
const methods = ['cancel', 'constructor', 'getReader', 'pipeThrough', 'pipeTo', 'tee', 'getIterator'];
const properties = methods.concat(['locked']).sort();

const rs = new ReadableStream();
Expand Down Expand Up @@ -73,6 +73,7 @@ test(() => {
assert_equals(rs.pipeThrough.length, 2, 'pipeThrough should have 2 parameters');
assert_equals(rs.pipeTo.length, 1, 'pipeTo should have 1 parameter');
assert_equals(rs.tee.length, 0, 'tee should have no parameters');
assert_equals(rs.getIterator.length, 0, 'getIterator should have no required parameters');

}, 'ReadableStream instances should have the correct list of properties');

Expand Down