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streams: simplify readableStreamFromIterable #62651

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51 changes: 23 additions & 28 deletions lib/internal/webstreams/readablestream.js
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@ const {
Symbol,
SymbolAsyncIterator,
SymbolDispose,
SymbolIterator,
SymbolToStringTag,
TypedArrayPrototypeGetLength,
Uint8Array,
Expand All @@ -32,6 +33,7 @@ const {
const {
AbortError,
codes: {
ERR_ARG_NOT_ITERABLE,
ERR_ILLEGAL_CONSTRUCTOR,
ERR_INVALID_ARG_TYPE,
ERR_INVALID_ARG_VALUE,
Expand Down Expand Up @@ -110,8 +112,6 @@ const {
nonOpCancel,
nonOpPull,
nonOpStart,
getIterator,
iteratorNext,
kType,
kState,
} = require('internal/webstreams/util');
Expand Down Expand Up @@ -1341,41 +1341,36 @@ function createReadableStreamState() {

function readableStreamFromIterable(iterable) {
let stream;
const iteratorRecord = getIterator(iterable, 'async');

const iteratorGetter = iterable[SymbolAsyncIterator] ?? iterable[SymbolIterator];
if (iteratorGetter == null || typeof iteratorGetter !== 'function') {
throw new ERR_ARG_NOT_ITERABLE(iterable);
}
const iterator = FunctionPrototypeCall(iteratorGetter, iterable);
const startAlgorithm = nonOpStart;

async function pullAlgorithm() {
const nextResult = iteratorNext(iteratorRecord);
const nextPromise = PromiseResolve(nextResult);
return PromisePrototypeThen(nextPromise, (iterResult) => {
if (typeof iterResult !== 'object' || iterResult === null) {
throw new ERR_INVALID_STATE.TypeError(
'The promise returned by the iterator.next() method must fulfill with an object');
}
if (iterResult.done) {
readableStreamDefaultControllerClose(stream[kState].controller);
} else {
readableStreamDefaultControllerEnqueue(stream[kState].controller, iterResult.value);
}
});
const iterResult = await iterator.next();
if (typeof iterResult !== 'object' || iterResult === null) {
throw new ERR_INVALID_STATE.TypeError(
'The promise returned by the iterator.next() method must fulfill with an object');
}
if (iterResult.done) {
readableStreamDefaultControllerClose(stream[kState].controller);
} else {
readableStreamDefaultControllerEnqueue(stream[kState].controller, await iterResult.value);
}
}

async function cancelAlgorithm(reason) {
const iterator = iteratorRecord.iterator;
const returnMethod = iterator.return;
if (returnMethod === undefined) {
return PromiseResolve();
return;
}
const iterResult = await FunctionPrototypeCall(returnMethod, iterator, reason);
if (typeof iterResult !== 'object' || iterResult === null) {
throw new ERR_INVALID_STATE.TypeError(
'The promise returned by the iterator.return() method must fulfill with an object');
}
const returnResult = FunctionPrototypeCall(returnMethod, iterator, reason);
const returnPromise = PromiseResolve(returnResult);
return PromisePrototypeThen(returnPromise, (iterResult) => {
if (typeof iterResult !== 'object' || iterResult === null) {
throw new ERR_INVALID_STATE.TypeError(
'The promise returned by the iterator.return() method must fulfill with an object');
}
return undefined;
});
}

stream = createReadableStream(
Expand Down
64 changes: 0 additions & 64 deletions lib/internal/webstreams/util.js
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Original file line number Diff line number Diff line change
Expand Up @@ -13,16 +13,12 @@ const {
PromisePrototypeThen,
ReflectGet,
Symbol,
SymbolAsyncIterator,
SymbolIterator,
Uint8Array,
} = primordials;

const {
codes: {
ERR_ARG_NOT_ITERABLE,
ERR_INVALID_ARG_VALUE,
ERR_INVALID_STATE,
},
} = require('internal/errors');

Expand Down Expand Up @@ -208,64 +204,6 @@ function lazyTransfer() {
return transfer;
}

function createAsyncFromSyncIterator(syncIteratorRecord) {
const syncIterable = {
[SymbolIterator]: () => syncIteratorRecord.iterator,
};

const asyncIterator = (async function* () {
return yield* syncIterable;
}());

const nextMethod = asyncIterator.next;
return { iterator: asyncIterator, nextMethod, done: false };
}

// Refs: https://tc39.es/ecma262/#sec-getiterator
function getIterator(obj, kind = 'sync', method) {
if (method === undefined) {
if (kind === 'async') {
method = obj[SymbolAsyncIterator];
if (method == null) {
const syncMethod = obj[SymbolIterator];

if (syncMethod === undefined) {
throw new ERR_ARG_NOT_ITERABLE(obj);
}

const syncIteratorRecord = getIterator(obj, 'sync', syncMethod);
return createAsyncFromSyncIterator(syncIteratorRecord);
}
} else {
method = obj[SymbolIterator];
}
}

if (method === undefined) {
throw new ERR_ARG_NOT_ITERABLE(obj);
}

const iterator = FunctionPrototypeCall(method, obj);
if (typeof iterator !== 'object' || iterator === null) {
throw new ERR_INVALID_STATE.TypeError('The iterator method must return an object');
}
const nextMethod = iterator.next;
return { iterator, nextMethod, done: false };
}

function iteratorNext(iteratorRecord, value) {
let result;
if (value === undefined) {
result = FunctionPrototypeCall(iteratorRecord.nextMethod, iteratorRecord.iterator);
} else {
result = FunctionPrototypeCall(iteratorRecord.nextMethod, iteratorRecord.iterator, [value]);
}
if (typeof result !== 'object' || result === null) {
throw new ERR_INVALID_STATE.TypeError('The iterator.next() method must return an object');
}
return result;
}

module.exports = {
ArrayBufferViewGetBuffer,
ArrayBufferViewGetByteLength,
Expand All @@ -292,8 +230,6 @@ module.exports = {
nonOpPull,
nonOpStart,
nonOpWrite,
getIterator,
iteratorNext,
kType,
kState,
};
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