stream: duplexify

PR-URL: #39519
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

doc/api/stream.md

@@ -2081,6 +2081,34 @@ added: REPLACEME
 * `streamWritable` {stream.Writable}
 * Returns: {WritableStream}
 
+### `stream.Duplex.from(src)`
+<!-- YAML
+added: REPLACEME
+-->
+
+* `src` {Stream|Blob|ArrayBuffer|string|Iterable|AsyncIterable|
+  AsyncGeneratorFunction|AsyncFunction|Promise|Object}
+
+A utility method for creating duplex streams.
+
+* `Stream` converts writable stream into writable `Duplex` and readable stream
+  to `Duplex`.
+* `Blob` converts into readable `Duplex`.
+* `string` converts into readable `Duplex`.
+* `ArrayBuffer` converts into readable `Duplex`.
+* `AsyncIterable` converts into a readable `Duplex`. Cannot yield
+  `null`.
+* `AsyncGeneratorFunction` converts into a readable/writable transform
+  `Duplex`. Must take a source `AsyncIterable` as first parameter. Cannot yield
+  `null`.
+* `AsyncFunction` converts into a writable `Duplex`. Must return
+  either `null` or `undefined`
+* `Object ({ writable, readable })` converts `readable` and
+  `writable` into `Stream` and then combines them into `Duplex` where the
+  `Duplex` will write to the `writable` and read from the `readable`.
+* `Promise` converts into readable `Duplex`. Value `null` is ignored.
+* Returns: {stream.Duplex}
+
 ### `stream.Duplex.fromWeb(pair[, options])`
 <!-- YAML
 added: REPLACEME

lib/internal/streams/compose.js

@@ -2,28 +2,19 @@
 
 const pipeline = require('internal/streams/pipeline');
 const Duplex = require('internal/streams/duplex');
-const { createDeferredPromise } = require('internal/util');
 const { destroyer } = require('internal/streams/destroy');
-const from = require('internal/streams/from');
 const {
   isNodeStream,
-  isIterable,
   isReadable,
   isWritable,
 } = require('internal/streams/utils');
-const {
-  PromiseResolve,
-} = primordials;
 const {
   AbortError,
   codes: {
-    ERR_INVALID_ARG_TYPE,
     ERR_INVALID_ARG_VALUE,
-    ERR_INVALID_RETURN_VALUE,
     ERR_MISSING_ARGS,
   },
 } = require('internal/errors');
-const assert = require('internal/assert');
 
 // This is needed for pre node 17.
 class ComposeDuplex extends Duplex {
@@ -53,18 +44,18 @@ module.exports = function compose(...streams) {
   }
 
   if (streams.length === 1) {
-    return makeDuplex(streams[0], 'streams[0]');
+    return Duplex.from(streams[0]);
   }
 
   const orgStreams = [...streams];
 
   if (typeof streams[0] === 'function') {
-    streams[0] = makeDuplex(streams[0], 'streams[0]');
+    streams[0] = Duplex.from(streams[0]);
   }
 
   if (typeof streams[streams.length - 1] === 'function') {
     const idx = streams.length - 1;
-    streams[idx] = makeDuplex(streams[idx], `streams[${idx}]`);
+    streams[idx] = Duplex.from(streams[idx]);
   }
 
   for (let n = 0; n < streams.length; ++n) {
@@ -117,7 +108,7 @@ module.exports = function compose(...streams) {
   // Implement Writable/Readable/Duplex traits.
   // See, https://github.com/nodejs/node/pull/33515.
   d = new ComposeDuplex({
-    highWaterMark: 1,
+    // TODO (ronag): highWaterMark?
     writableObjectMode: !!head?.writableObjectMode,
     readableObjectMode: !!tail?.writableObjectMode,
     writable,
@@ -203,82 +194,3 @@ module.exports = function compose(...streams) {
 
   return d;
 };
-
-function makeDuplex(stream, name) {
-  let ret;
-  if (typeof stream === 'function') {
-    assert(stream.length > 0);
-
-    const { value, write, final } = fromAsyncGen(stream);
-
-    if (isIterable(value)) {
-      ret = from(ComposeDuplex, value, {
-        objectMode: true,
-        highWaterMark: 1,
-        write,
-        final
-      });
-    } else if (typeof value?.then === 'function') {
-      const promise = PromiseResolve(value)
-        .then((val) => {
-          if (val != null) {
-            throw new ERR_INVALID_RETURN_VALUE('nully', name, val);
-          }
-        })
-        .catch((err) => {
-          destroyer(ret, err);
-        });
-
-      ret = new ComposeDuplex({
-        objectMode: true,
-        highWaterMark: 1,
-        readable: false,
-        write,
-        final(cb) {
-          final(() => promise.then(cb, cb));
-        }
-      });
-    } else {
-      throw new ERR_INVALID_RETURN_VALUE(
-        'Iterable, AsyncIterable or AsyncFunction', name, value);
-    }
-  } else if (isNodeStream(stream)) {
-    ret = stream;
-  } else if (isIterable(stream)) {
-    ret = from(ComposeDuplex, stream, {
-      objectMode: true,
-      highWaterMark: 1,
-      writable: false
-    });
-  } else {
-    throw new ERR_INVALID_ARG_TYPE(
-      name,
-      ['Stream', 'Iterable', 'AsyncIterable', 'Function'],
-      stream)
-    ;
-  }
-  return ret;
-}
-
-function fromAsyncGen(fn) {
-  let { promise, resolve } = createDeferredPromise();
-  const value = fn(async function*() {
-    while (true) {
-      const { chunk, done, cb } = await promise;
-      process.nextTick(cb);
-      if (done) return;
-      yield chunk;
-      ({ promise, resolve } = createDeferredPromise());
-    }
-  }());
-
-  return {
-    value,
-    write(chunk, encoding, cb) {
-      resolve({ chunk, done: false, cb });
-    },
-    final(cb) {
-      resolve({ done: true, cb });
-    }
-  };
-}

lib/internal/streams/destroy.js

@@ -323,7 +323,7 @@ function emitErrorCloseLegacy(stream, err) {
 
 // Normalize destroy for legacy.
 function destroyer(stream, err) {
-  if (isDestroyed(stream)) {
+  if (!stream || isDestroyed(stream)) {
     return;
   }
 

lib/internal/streams/duplex.js

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