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test_async_iterable_stream_cleanup.cjs
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test_async_iterable_stream_cleanup.cjs
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function assert(condition, message) {
if (!condition) throw new Error(message);
}
function assertEq(actual, expected, message) {
if (actual !== expected) {
throw new Error(`${message}: expected ${expected}, got ${actual}`);
}
}
function createAsyncIterableStream(source, trace) {
const stream = source.pipeThrough(new TransformStream());
stream[Symbol.asyncIterator] = function() {
const reader = this.getReader();
let finished = false;
async function cleanup(cancelStream) {
if (finished) return;
finished = true;
try {
if (cancelStream) {
trace.push('cleanup-before-cancel');
await reader.cancel();
trace.push('cleanup-after-cancel');
}
} finally {
trace.push('cleanup-before-releaseLock');
reader.releaseLock();
trace.push('cleanup-after-releaseLock');
}
}
return {
async next() {
const result = await reader.read();
if (result.done) {
await cleanup(false);
return { done: true, value: void 0 };
}
trace.push(`next:${result.value}`);
return { done: false, value: result.value };
},
async return() {
trace.push('return-start');
await cleanup(true);
trace.push('return-end');
return { done: true, value: void 0 };
},
};
};
return stream;
}
async function main() {
const trace = [];
const source = new ReadableStream({
start(controller) {
controller.enqueue('alpha');
controller.enqueue('beta');
controller.close();
},
cancel() {
trace.push('source-cancel');
},
});
const stream = createAsyncIterableStream(source, trace);
assert(typeof stream[Symbol.asyncIterator] === 'function', 'stream should expose @@asyncIterator');
for await (const chunk of stream) {
trace.push(`chunk:${chunk}`);
break;
}
trace.push('loop-exit');
assertEq(
trace.join(','),
[
'next:alpha',
'chunk:alpha',
'return-start',
'cleanup-before-cancel',
'cleanup-after-cancel',
'cleanup-before-releaseLock',
'cleanup-after-releaseLock',
'return-end',
'loop-exit',
].join(','),
'for-await cleanup should finish after cancel/releaseLock'
);
console.log('async iterable stream cleanup survives cancel/releaseLock');
}
main().catch((err) => {
console.error(err && err.stack ? err.stack : String(err));
throw err;
});

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test_async_iterable_stream_cleanup.cjs (2 KB)

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