stream: duplexify

PR-URL: nodejs#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

@@ -1943,6 +1943,34 @@ Calling `Readable.from(string)` or `Readable.from(buffer)` will not have
 the strings or buffers be iterated to match the other streams semantics
 for performance reasons.
 
+### `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.addAbortSignal(signal, stream)`
 <!-- YAML
 added: v15.4.0

lib/internal/streams/destroy.js

@@ -307,6 +307,7 @@ function isRequest(stream) {
 
 // Normalize destroy for legacy.
 function destroyer(stream, err) {
+  if (!stream) return;
   if (isRequest(stream)) return stream.abort();
   if (isRequest(stream.req)) return stream.req.abort();
   if (typeof stream.destroy === 'function') return stream.destroy(err);

lib/internal/streams/duplex.js

@@ -108,3 +108,12 @@ ObjectDefineProperties(Duplex.prototype, {
     }
   }
 });
+
+let duplexify;
+
+Duplex.from = function(body) {
+  if (!duplexify) {
+    duplexify = require('internal/streams/duplexify');
+  }
+  return duplexify(body, 'body');
+};