https: make opts optional & immutable when create

`opts` in `createServer` will be immutable that won't change origional
opts value. What's more, it's optional which can make `requestListener`
be the first argument.

PR-URL: #13599
Fixes: #13584
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yorkie Liu <yorkiefixer@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>

Author: XadillaX

doc/api/https.md

@@ -46,7 +46,7 @@ added: v8.0.0
 
 See [`http.Server#keepAliveTimeout`][].
 
-## https.createServer(options[, requestListener])
+## https.createServer([options][, requestListener])
 <!-- YAML
 added: v0.3.4
 -->

lib/https.js

@@ -34,6 +34,12 @@ const { urlToOptions, searchParamsSymbol } = require('internal/url');
 function Server(opts, requestListener) {
   if (!(this instanceof Server)) return new Server(opts, requestListener);
 
+  if (typeof opts === 'function') {
+    requestListener = opts;
+    opts = undefined;
+  }
+  opts = util._extend({}, opts);
+
   if (process.features.tls_npn && !opts.NPNProtocols) {
     opts.NPNProtocols = ['http/1.1', 'http/1.0'];
   }

test/parallel/test-https-argument-of-creating.js

@@ -0,0 +1,44 @@
+'use strict';
+
+const common = require('../common');
+if (!common.hasCrypto) {
+  common.skip('missing crypto');
+  return;
+}
+
+const assert = require('assert');
+const https = require('https');
+const tls = require('tls');
+
+const dftProtocol = {};
+
+// test for immutable `opts`
+{
+  const opts = { foo: 'bar', NPNProtocols: [ 'http/1.1' ] };
+  const server = https.createServer(opts);
+
+  tls.convertNPNProtocols([ 'http/1.1' ], dftProtocol);
+  assert.deepStrictEqual(opts, { foo: 'bar', NPNProtocols: [ 'http/1.1' ] });
+  assert.strictEqual(server.NPNProtocols.compare(dftProtocol.NPNProtocols), 0);
+}
+
+
+// validate that `createServer` can work with the only argument requestListener
+{
+  const mustNotCall = common.mustNotCall();
+  const server = https.createServer(mustNotCall);
+
+  tls.convertNPNProtocols([ 'http/1.1', 'http/1.0' ], dftProtocol);
+  assert.strictEqual(server.NPNProtocols.compare(dftProtocol.NPNProtocols), 0);
+  assert.strictEqual(server.listeners('request').length, 1);
+  assert.strictEqual(server.listeners('request')[0], mustNotCall);
+}
+
+
+// validate that `createServer` can work with no arguments
+{
+  const server = https.createServer();
+
+  assert.strictEqual(server.NPNProtocols.compare(dftProtocol.NPNProtocols), 0);
+  assert.strictEqual(server.listeners('request').length, 0);
+}