stream: writable.end should return this.

PR-URL: #18780
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/stream.md

@@ -355,6 +355,9 @@ See also: [`writable.uncork()`][].
 <!-- YAML
 added: v0.9.4
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/18780
+    description: This method now returns a reference to `writable`.
   - version: v8.0.0
     pr-url: https://github.com/nodejs/node/pull/11608
     description: The `chunk` argument can now be a `Uint8Array` instance.
@@ -366,6 +369,7 @@ changes:
   other than `null`.
 * `encoding` {string} The encoding, if `chunk` is a string
 * `callback` {Function} Optional callback for when the stream is finished
+* Returns: {this}
 
 Calling the `writable.end()` method signals that no more data will be written
 to the [Writable][]. The optional `chunk` and `encoding` arguments allow one

lib/_stream_writable.js

@@ -570,6 +570,8 @@ Writable.prototype.end = function(chunk, encoding, cb) {
   // ignore unnecessary end() calls.
   if (!state.ending)
     endWritable(this, state, cb);
+
+  return this;
 };
 
 Object.defineProperty(Writable.prototype, 'writableLength', {

test/parallel/test-stream-writableState-ending.js

@@ -24,11 +24,14 @@ writable.on('finish', () => {
   testStates(true, true, true);
 });
 
-writable.end('testing function end()', () => {
+const result = writable.end('testing function end()', () => {
   // ending, finished, ended = true.
   testStates(true, true, true);
 });
 
+// end returns the writable instance
+assert.strictEqual(result, writable);
+
 // ending, ended = true.
 // finished = false.
 testStates(true, false, true);