http: OutgoingMessage change writable after end

When an OutgoingMessage is closed (for example, using the `end`
method), its 'writable' property should be changed to false - since it
is not writable anymore. The 'writable' property should have the
opposite value of the 'finished' property.

PR-URL: https://github.com/nodejs/node/pull/14024
Fixes: https://github.com/nodejs/node/issues/14023
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>

lib/_http_outgoing.js

@@ -793,6 +793,7 @@ OutgoingMessage.prototype.end = function end(chunk, encoding, callback) {
     this.connection.uncork();
 
   this.finished = true;
+  this.writable = false;
 
   // There is the first message on the outgoing queue, and we've sent
   // everything to the socket.

test/parallel/test-http-outgoing-finish-writable.js

@@ -0,0 +1,31 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
+
+// Verify that after calling end() on an `OutgoingMessage` (or a type that
+// inherits from `OutgoingMessage`), its `writable` property is set to false.
+
+const server = http.createServer(common.mustCall(function(req, res) {
+  assert.strictEqual(res.writable, true);
+  assert.strictEqual(res.finished, false);
+  res.end();
+  assert.strictEqual(res.writable, false);
+  assert.strictEqual(res.finished, true);
+
+  server.close();
+}));
+
+server.listen(0);
+
+server.on('listening', common.mustCall(function() {
+  const clientRequest = http.request({
+    port: server.address().port,
+    method: 'GET',
+    path: '/'
+  });
+
+  assert.strictEqual(clientRequest.writable, true);
+  clientRequest.end();
+  assert.strictEqual(clientRequest.writable, false);
+}));

test/parallel/test-pipe-outgoing-message-data-emitted-after-ended.js

@@ -0,0 +1,39 @@
+'use strict';
+const common = require('../common');
+const http = require('http');
+const util = require('util');
+const stream = require('stream');
+
+// Verify that when piping a stream to an `OutgoingMessage` (or a type that
+// inherits from `OutgoingMessage`), if data is emitted after the
+// `OutgoingMessage` was closed - no `write after end` error is raised (this
+// should be the case when piping - when writing data directly to the
+// `OutgoingMessage` this error should be raised).
+
+function MyStream() {
+  stream.call(this);
+}
+util.inherits(MyStream, stream);
+
+const server = http.createServer(common.mustCall(function(req, res) {
+  const myStream = new MyStream();
+  myStream.pipe(res);
+
+  process.nextTick(common.mustCall(() => {
+    res.end();
+    myStream.emit('data', 'some data');
+
+    // If we got here - 'write after end' wasn't raised and the test passed.
+    process.nextTick(common.mustCall(() => server.close()));
+  }));
+}));
+
+server.listen(0);
+
+server.on('listening', common.mustCall(function() {
+  http.request({
+    port: server.address().port,
+    method: 'GET',
+    path: '/'
+  }).end();
+}));