Revert "util: move util._extend to eol"

This reverts commit ac97a532f5.

PR-URL: https://github.com/nodejs/node/pull/53429
Refs: https://github.com/tape-testing/tape/issues/607
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: James M Snell <jasnell@gmail.com>

benchmark/es/spread-assign.js

@@ -1,9 +1,10 @@
 'use strict';
 
 const common = require('../common.js');
+const util = require('util');
 
 const bench = common.createBenchmark(main, {
-  method: ['spread', 'assign'],
+  method: ['spread', 'assign', '_extend'],
   count: [5, 10, 20],
   n: [1e6],
 });
@@ -17,6 +18,12 @@ function main({ n, context, count, rest, method }) {
   let obj;
 
   switch (method) {
+    case '_extend':
+      bench.start();
+      for (let i = 0; i < n; i++)
+        obj = util._extend({}, src);
+      bench.end(n);
+      break;
     case 'assign':
       bench.start();
       for (let i = 0; i < n; i++)

benchmark/misc/util-extend-vs-object-assign.js

@@ -0,0 +1,30 @@
+'use strict';
+
+const common = require('../common.js');
+const util = require('util');
+
+const bench = common.createBenchmark(main, {
+  type: ['extend', 'assign'],
+  n: [10e4],
+});
+
+function main({ n, type }) {
+  let fn;
+  if (type === 'extend') {
+    fn = util._extend;
+  } else if (type === 'assign') {
+    fn = Object.assign;
+  }
+
+  // Force-optimize the method to test so that the benchmark doesn't
+  // get disrupted by the optimizer kicking in halfway through.
+  for (let i = 0; i < type.length * 10; i += 1)
+    fn({}, process.env);
+
+  const obj = new Proxy({}, { set: function(a, b, c) { return true; } });
+
+  bench.start();
+  for (let j = 0; j < n; j += 1)
+    fn(obj, process.env);
+  bench.end(n);
+}

doc/api/deprecations.md

@@ -1408,9 +1408,6 @@ requirements and complexity of your application.
 
 <!-- YAML
 changes:
-  - version: REPLACEME
-    pr-url: https://github.com/nodejs/node/pull/52744
-    description: End-of-Life deprecation.
   - version: v22.0.0
     pr-url: https://github.com/nodejs/node/pull/50488
     description: Runtime deprecation.
@@ -1422,9 +1419,9 @@ changes:
     description: Documentation-only deprecation.
 -->
 
-Type: End-of-Life
+Type: Runtime
 
-The `util._extend()` API has been removed because it's an unmaintained
+The [`util._extend()`][] API is deprecated because it's an unmaintained
 legacy API that was exposed to user land by accident.
 Please use `target = Object.assign(target, source)` instead.
 
@@ -3836,6 +3833,7 @@ and [`crypto.setEngine()`][] all depend on this functionality from OpenSSL.
 [`url.format()`]: url.md#urlformaturlobject
 [`url.parse()`]: url.md#urlparseurlstring-parsequerystring-slashesdenotehost
 [`url.resolve()`]: url.md#urlresolvefrom-to
+[`util._extend()`]: util.md#util_extendtarget-source
 [`util.getSystemErrorName()`]: util.md#utilgetsystemerrornameerr
 [`util.inspect()`]: util.md#utilinspectobject-options
 [`util.inspect.custom`]: util.md#utilinspectcustom

doc/api/util.md

@@ -2923,6 +2923,24 @@ util.types.isWeakSet(new WeakSet());  // Returns true
 The following APIs are deprecated and should no longer be used. Existing
 applications and modules should be updated to find alternative approaches.
 
+### `util._extend(target, source)`
+
+<!-- YAML
+added: v0.7.5
+deprecated: v6.0.0
+-->
+
+> Stability: 0 - Deprecated: Use [`Object.assign()`][] instead.
+
+* `target` {Object}
+* `source` {Object}
+
+The `util._extend()` method was never intended to be used outside of internal
+Node.js modules. The community found and used it anyway.
+
+It is deprecated and should not be used in new code. JavaScript comes with very
+similar built-in functionality through [`Object.assign()`][].
+
 ### `util.isArray(object)`
 
 <!-- YAML
@@ -2972,6 +2990,7 @@ util.isArray({});
 [`JSON.stringify()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify
 [`MIMEparams`]: #class-utilmimeparams
 [`Map`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map
+[`Object.assign()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign
 [`Object.freeze()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze
 [`Promise`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise
 [`Proxy`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy

lib/util.js

@@ -153,6 +153,26 @@ function inherits(ctor, superCtor) {
   ObjectSetPrototypeOf(ctor.prototype, superCtor.prototype);
 }
 
+/**
+ * @deprecated since v6.0.0
+ * @template T
+ * @template S
+ * @param {T} target
+ * @param {S} source
+ * @returns {S extends null ? T : (T & S)}
+ */
+function _extend(target, source) {
+  // Don't do anything if source isn't an object
+  if (source === null || typeof source !== 'object') return target;
+
+  const keys = ObjectKeys(source);
+  let i = keys.length;
+  while (i--) {
+    target[keys[i]] = source[keys[i]];
+  }
+  return target;
+}
+
 const callbackifyOnRejected = (reason, cb) => {
   // `!reason` guard inspired by bluebird (Ref: https://goo.gl/t5IS6M).
   // Because `null` is a special error value in callbacks which means "no error
@@ -259,6 +279,9 @@ function parseEnv(content) {
 module.exports = {
   _errnoException,
   _exceptionWithHostPort,
+  _extend: deprecate(_extend,
+                     'The `util._extend` API is deprecated. Please use Object.assign() instead.',
+                     'DEP0060'),
   callbackify,
   debug: debuglog,
   debuglog,

test/fixtures/tls-connect.js

@@ -57,7 +57,7 @@ exports.connect = function connect(options, callback) {
     }).listen(0, function() {
       server.server = this;
 
-      const optClient = Object.assign({
+      const optClient = util._extend({
         port: this.address().port,
       }, options.client);
 

test/parallel/test-util.js

@@ -40,6 +40,15 @@ assert.strictEqual(util.isArray(/regexp/), false);
 assert.strictEqual(util.isArray(new Error()), false);
 assert.strictEqual(util.isArray({ __proto__: Array.prototype }), false);
 
+// _extend
+assert.deepStrictEqual(util._extend({ a: 1 }), { a: 1 });
+assert.deepStrictEqual(util._extend({ a: 1 }, []), { a: 1 });
+assert.deepStrictEqual(util._extend({ a: 1 }, null), { a: 1 });
+assert.deepStrictEqual(util._extend({ a: 1 }, true), { a: 1 });
+assert.deepStrictEqual(util._extend({ a: 1 }, false), { a: 1 });
+assert.deepStrictEqual(util._extend({ a: 1 }, { b: 2 }), { a: 1, b: 2 });
+assert.deepStrictEqual(util._extend({ a: 1, b: 2 }, { b: 3 }), { a: 1, b: 3 });
+
 assert.strictEqual(util.toUSVString('string\ud801'), 'string\ufffd');
 
 {