util: preserve length of deprecated functions

LiviaMedeiros · RafaelGSS · commit 8ca56a8db88d · 2025-05-02T17:06:17.000-03:00
PR-URL: #57806 Reviewed-By: Jordan Harband <ljharb@gmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>
diff --git a/lib/internal/util.js b/lib/internal/util.js
@@ -142,6 +142,12 @@ function pendingDeprecate(fn, msg, code) {
     emitDeprecationWarning();
     return ReflectApply(fn, this, args);
   }
+
+  ObjectDefineProperty(deprecated, 'length', {
+    __proto__: null,
+    ...ObjectGetOwnPropertyDescriptor(fn, 'length'),
+  });
+
   return deprecated;
 }
 
@@ -180,6 +186,11 @@ function deprecate(fn, msg, code, useEmitSync) {
     deprecated.prototype = fn.prototype;
   }
 
+  ObjectDefineProperty(deprecated, 'length', {
+    __proto__: null,
+    ...ObjectGetOwnPropertyDescriptor(fn, 'length'),
+  });
+
   return deprecated;
 }
 
diff --git a/test/parallel/test-util-deprecate.js b/test/parallel/test-util-deprecate.js
@@ -1,3 +1,4 @@
+// Flags: --expose-internals
 'use strict';
 
 require('../common');
@@ -6,9 +7,27 @@ require('../common');
 
 const assert = require('assert');
 const util = require('util');
+const internalUtil = require('internal/util');
 
 const expectedWarnings = new Map();
 
+// Deprecated function length is preserved
+for (const fn of [
+  function() {},
+  function(a) {},
+  function(a, b, c) {},
+  function(...args) {},
+  function(a, b, c, ...args) {},
+  () => {},
+  (a) => {},
+  (a, b, c) => {},
+  (...args) => {},
+  (a, b, c, ...args) => {},
+]) {
+  assert.strictEqual(util.deprecate(fn).length, fn.length);
+  assert.strictEqual(internalUtil.pendingDeprecate(fn).length, fn.length);
+}
+
 // Emits deprecation only once if same function is called.
 {
   const msg = 'fhqwhgads';

Original file line number	Diff line number	Diff line change
`@@ -142,6 +142,12 @@ function pendingDeprecate(fn, msg, code) {`
`142`	`142`	`emitDeprecationWarning();`
`143`	`143`	`return ReflectApply(fn, this, args);`
`144`	`144`	`}`
	`145`	`+`
	`146`	`+ ObjectDefineProperty(deprecated, 'length', {`
	`147`	`+ __proto__: null,`
	`148`	`+ ...ObjectGetOwnPropertyDescriptor(fn, 'length'),`
	`149`	`+ });`
	`150`	`+`
`145`	`151`	`return deprecated;`
`146`	`152`	`}`
`147`	`153`
`@@ -180,6 +186,11 @@ function deprecate(fn, msg, code, useEmitSync) {`
`180`	`186`	`deprecated.prototype = fn.prototype;`
`181`	`187`	`}`
`182`	`188`
	`189`	`+ ObjectDefineProperty(deprecated, 'length', {`
	`190`	`+ __proto__: null,`
	`191`	`+ ...ObjectGetOwnPropertyDescriptor(fn, 'length'),`
	`192`	`+ });`
	`193`	`+`
`183`	`194`	`return deprecated;`
`184`	`195`	`}`
`185`	`196`