child_process: handling fork( path, undefined / null, obj )

lib/child_process.js

@@ -69,6 +69,11 @@ exports.fork = function fork(modulePath /* , args, options */) {
     args = arguments[pos++];
   }
 
+  if (pos < arguments.length && (arguments[pos] === undefined ||
+      arguments[pos] === null)) {
+    pos++;
+  }
+
   if (pos < arguments.length && arguments[pos] != null) {
     if (typeof arguments[pos] !== 'object') {
       throw new ERR_INVALID_ARG_VALUE(`arguments[${pos}]`, arguments[pos]);

test/fixtures/child-process-echo-options.js

@@ -0,0 +1,2 @@
+process.send({ env: process.env });
+process.exit(0);

test/parallel/test-child-process-fork-options.js

@@ -0,0 +1,17 @@
+/**
+ * fork should parse options correctly if args is undefined or null
+ */
+
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const { fork } = require('child_process');
+const fixtures = require('../common/fixtures');
+
+const expectedEnv = { foo: 'bar' };
+const cp = fork(fixtures.path('child-process-echo-options.js'), undefined,
+                { env: Object.assign({}, expectedEnv) });
+
+cp.on('message', common.mustCall(function({ env }) {
+  assert.strictEqual(env.foo, expectedEnv.foo);
+}));