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stream: duplexify
PR-URL: nodejs/node#39519 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
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Lines changed: 560 additions & 111 deletions

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‎doc/api/stream.md‎

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* `streamWritable` {stream.Writable}
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* Returns: {WritableStream}
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### `stream.Duplex.from(src)`
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<!-- YAML
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added: REPLACEME
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-->
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* `src` {Stream|Blob|ArrayBuffer|string|Iterable|AsyncIterable|
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AsyncGeneratorFunction|AsyncFunction|Promise|Object}
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A utility method for creating duplex streams.
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* `Stream` converts writable stream into writable `Duplex` and readable stream
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to `Duplex`.
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* `Blob` converts into readable `Duplex`.
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* `string` converts into readable `Duplex`.
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* `ArrayBuffer` converts into readable `Duplex`.
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* `AsyncIterable` converts into a readable `Duplex`. Cannot yield
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`null`.
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* `AsyncGeneratorFunction` converts into a readable/writable transform
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`Duplex`. Must take a source `AsyncIterable` as first parameter. Cannot yield
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`null`.
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* `AsyncFunction` converts into a writable `Duplex`. Must return
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either `null` or `undefined`
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* `Object ({ writable, readable })` converts `readable` and
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`writable` into `Stream` and then combines them into `Duplex` where the
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`Duplex` will write to the `writable` and read from the `readable`.
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* `Promise` converts into readable `Duplex`. Value `null` is ignored.
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* Returns: {stream.Duplex}
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### `stream.Duplex.fromWeb(pair[, options])`
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<!-- YAML
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added: REPLACEME

‎lib/internal/streams/compose.js‎

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@@ -2,28 +2,19 @@
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const pipeline = require('internal/streams/pipeline');
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const Duplex = require('internal/streams/duplex');
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const { createDeferredPromise } = require('internal/util');
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const { destroyer } = require('internal/streams/destroy');
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const from = require('internal/streams/from');
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const {
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isNodeStream,
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isIterable,
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isReadable,
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isWritable,
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} = require('internal/streams/utils');
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const {
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PromiseResolve,
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} = primordials;
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const {
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AbortError,
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codes: {
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ERR_INVALID_ARG_TYPE,
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ERR_INVALID_ARG_VALUE,
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ERR_INVALID_RETURN_VALUE,
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ERR_MISSING_ARGS,
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},
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} = require('internal/errors');
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const assert = require('internal/assert');
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// This is needed for pre node 17.
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class ComposeDuplex extends Duplex {
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}
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if (streams.length === 1) {
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return makeDuplex(streams[0], 'streams[0]');
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return Duplex.from(streams[0]);
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}
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const orgStreams = [...streams];
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if (typeof streams[0] === 'function') {
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streams[0] = makeDuplex(streams[0], 'streams[0]');
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streams[0] = Duplex.from(streams[0]);
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}
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if (typeof streams[streams.length - 1] === 'function') {
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const idx = streams.length - 1;
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streams[idx] = makeDuplex(streams[idx], `streams[${idx}]`);
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streams[idx] = Duplex.from(streams[idx]);
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}
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for (let n = 0; n < streams.length; ++n) {
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// Implement Writable/Readable/Duplex traits.
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// See, https://github.com/nodejs/node/pull/33515.
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d = new ComposeDuplex({
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highWaterMark: 1,
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// TODO (ronag): highWaterMark?
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writableObjectMode: !!head?.writableObjectMode,
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readableObjectMode: !!tail?.writableObjectMode,
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writable,
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return d;
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};
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function makeDuplex(stream, name) {
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let ret;
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if (typeof stream === 'function') {
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assert(stream.length > 0);
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const { value, write, final } = fromAsyncGen(stream);
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if (isIterable(value)) {
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ret = from(ComposeDuplex, value, {
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objectMode: true,
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highWaterMark: 1,
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write,
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final
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});
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} else if (typeof value?.then === 'function') {
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const promise = PromiseResolve(value)
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.then((val) => {
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if (val != null) {
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throw new ERR_INVALID_RETURN_VALUE('nully', name, val);
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}
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})
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.catch((err) => {
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destroyer(ret, err);
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});
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ret = new ComposeDuplex({
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objectMode: true,
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highWaterMark: 1,
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readable: false,
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write,
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final(cb) {
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final(() => promise.then(cb, cb));
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}
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});
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} else {
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throw new ERR_INVALID_RETURN_VALUE(
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'Iterable, AsyncIterable or AsyncFunction', name, value);
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}
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} else if (isNodeStream(stream)) {
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ret = stream;
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} else if (isIterable(stream)) {
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ret = from(ComposeDuplex, stream, {
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objectMode: true,
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highWaterMark: 1,
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writable: false
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});
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} else {
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throw new ERR_INVALID_ARG_TYPE(
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name,
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['Stream', 'Iterable', 'AsyncIterable', 'Function'],
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stream)
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;
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}
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return ret;
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}
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function fromAsyncGen(fn) {
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let { promise, resolve } = createDeferredPromise();
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const value = fn(async function*() {
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while (true) {
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const { chunk, done, cb } = await promise;
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process.nextTick(cb);
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if (done) return;
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yield chunk;
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({ promise, resolve } = createDeferredPromise());
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}
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}());
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return {
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value,
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write(chunk, encoding, cb) {
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resolve({ chunk, done: false, cb });
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},
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final(cb) {
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resolve({ done: true, cb });
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}
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};
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}

‎lib/internal/streams/destroy.js‎

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// Normalize destroy for legacy.
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function destroyer(stream, err) {
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if (isDestroyed(stream)) {
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if (!stream || isDestroyed(stream)) {
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return;
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}
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‎lib/internal/streams/duplex.js‎

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@@ -133,3 +133,12 @@ Duplex.fromWeb = function(pair, options) {
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Duplex.toWeb = function(duplex) {
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return lazyWebStreams().newReadableWritablePairFromDuplex(duplex);
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};
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let duplexify;
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Duplex.from = function(body) {
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if (!duplexify) {
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duplexify = require('internal/streams/duplexify');
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}
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return duplexify(body, 'body');
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};

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