util: add skipPrototype option to deep equality checks

doc/api/assert.md

@@ -229,11 +229,20 @@
 
 ### `new assert.Assert([options])`
 
+<!-- YAML
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/00000
+    description: Added `skipPrototypeComparison` option.
+-->
+
 * `options` {Object}
   * `diff` {string} If set to `'full'`, shows the full diff in assertion errors. Defaults to `'simple'`.
     Accepted values: `'simple'`, `'full'`.
   * `strict` {boolean} If set to `true`, non-strict methods behave like their
     corresponding strict methods. Defaults to `true`.
+  * `skipPrototypeComparison` {boolean} If set to `true`, skips prototype and constructor
+    comparison in deep equality checks. Defaults to `false`.
 
 Creates a new assertion instance. The `diff` option controls the verbosity of diffs in assertion error messages.
 
@@ -245,7 +254,8 @@
 ```
 
 **Important**: When destructuring assertion methods from an `Assert` instance,
-the methods lose their connection to the instance's configuration options (such as `diff` and `strict` settings).
+the methods lose their connection to the instance's configuration options (such
+as `diff`, `strict`, and `skipPrototypeComparison` settings).
 The destructured methods will fall back to default behavior instead.
 
 ```js
@@ -259,6 +269,33 @@
 strictEqual({ a: 1 }, { b: { c: 1 } });
 ```
 
+The `skipPrototypeComparison` option affects all deep equality methods:
+
+```js
+class Foo {
+  constructor(a) {
+    this.a = a;
+  }
+}
+
+class Bar {
+  constructor(a) {
+    this.a = a;
+  }
+}
+
+const foo = new Foo(1);
+const bar = new Bar(1);
+
+// Default behavior - fails due to different constructors
+const assert1 = new Assert();
+assert1.deepStrictEqual(foo, bar); // AssertionError
+
+// Skip prototype comparison - passes if properties are equal
+const assert2 = new Assert({ skipPrototypeComparison: true });
+assert2.deepStrictEqual(foo, bar); // OK
+```
+
 When destructured, methods lose access to the instance's `this` context and revert to default assertion behavior
 (diff: 'simple', non-strict mode).
 To maintain custom options when using destructured methods, avoid

doc/api/util.md

@@ -1553,19 +1553,57 @@
 console.log(arr); // logs the full array
 ```
 
-## `util.isDeepStrictEqual(val1, val2)`
+## `util.isDeepStrictEqual(val1, val2[, options])`
 
 <!-- YAML
 added: v9.0.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/00000
+    description: Added `options` parameter to allow skipping prototype comparison.
 -->
 
 * `val1` {any}
 * `val2` {any}
+* `options` {Object}
+  * `skipPrototypeComparison` {boolean} If `true`, prototype and constructor
+    comparison is skipped during deep strict equality check. **Default:** `false`.
 * Returns: {boolean}
 
 Returns `true` if there is deep strict equality between `val1` and `val2`.
 Otherwise, returns `false`.
 
+By default, deep strict equality includes comparison of object prototypes and
+constructors. When `options.skipPrototypeComparison` is `true`, objects with
+different prototypes or constructors can still be considered equal if their
+enumerable properties are deeply strictly equal.
+
+```js
+const util = require('node:util');
+
+class Foo {
+  constructor(a) {
+    this.a = a;
+  }
+}
+
+class Bar {
+  constructor(a) {
+    this.a = a;
+  }
+}
+
+const foo = new Foo(1);
+const bar = new Bar(1);
+
+// Different constructors, same properties
+console.log(util.isDeepStrictEqual(foo, bar));
+// false
+
+console.log(util.isDeepStrictEqual(foo, bar, { skipPrototypeComparison: true }));
+// true
+```
+
 See [`assert.deepStrictEqual()`][] for more information about deep strict
 equality.
 

lib/assert.js

@@ -93,6 +93,8 @@ const NO_EXCEPTION_SENTINEL = {};
  * @property {'full'|'simple'} [diff='simple'] - If set to 'full', shows the full diff in assertion errors.
  * @property {boolean} [strict=true] - If set to true, non-strict methods behave like their corresponding
  *   strict methods.
+ * @property {boolean} [skipPrototypeComparison=false] - If set to true, skips comparing prototypes
+ *   in deep equality checks.
  */
 
 /**
@@ -105,7 +107,7 @@ function Assert(options) {
     throw new ERR_CONSTRUCT_CALL_REQUIRED('Assert');
   }
 
-  options = ObjectAssign({ __proto__: null, strict: true }, options);
+  options = ObjectAssign({ __proto__: null, strict: true, skipPrototypeComparison: false }, options);
 
   const allowedDiffs = ['simple', 'full'];
   if (options.diff !== undefined) {
@@ -311,7 +313,10 @@ Assert.prototype.deepStrictEqual = function deepStrictEqual(actual, expected, me
     throw new ERR_MISSING_ARGS('actual', 'expected');
   }
   if (isDeepEqual === undefined) lazyLoadComparison();
-  if (!isDeepStrictEqual(actual, expected)) {
+  if (!isDeepStrictEqual(actual, expected, {
+    __proto__: null,
+    skipPrototypeComparison: this?.[kOptions]?.skipPrototypeComparison,
+  })) {
     innerFail({
       actual,
       expected,
@@ -337,7 +342,10 @@ function notDeepStrictEqual(actual, expected, message) {
     throw new ERR_MISSING_ARGS('actual', 'expected');
   }
   if (isDeepEqual === undefined) lazyLoadComparison();
-  if (isDeepStrictEqual(actual, expected)) {
+  if (isDeepStrictEqual(actual, expected, {
+    __proto__: null,
+    skipPrototypeComparison: this?.[kOptions]?.skipPrototypeComparison,
+  })) {
     innerFail({
       actual,
       expected,

lib/internal/util/comparisons.js

@@ -127,9 +127,10 @@ const {
   getOwnNonIndexProperties,
 } = internalBinding('util');
 
-const kStrict = 1;
+const kStrict = 2;
+const kStrictWithoutPrototypes = 3;
 const kLoose = 0;
-const kPartial = 2;
+const kPartial = 1;
 
 const kNoIterator = 0;
 const kIsArray = 1;
@@ -458,7 +459,7 @@ function keyCheck(val1, val2, mode, memos, iterationType, keys2) {
       }
     } else if (keys2.length !== (keys1 = ObjectKeys(val1)).length) {
       return false;
-    } else if (mode === kStrict) {
+    } else if (mode === kStrict || mode === kStrictWithoutPrototypes) {
       const symbolKeysA = getOwnSymbols(val1);
       if (symbolKeysA.length !== 0) {
         let count = 0;
@@ -1027,7 +1028,10 @@ module.exports = {
   isDeepEqual(val1, val2) {
     return detectCycles(val1, val2, kLoose);
   },
-  isDeepStrictEqual(val1, val2) {
+  isDeepStrictEqual(val1, val2, options) {
+    if (options?.skipPrototypeComparison) {
+      return detectCycles(val1, val2, kStrictWithoutPrototypes);
+    }
     return detectCycles(val1, val2, kStrict);
   },
   isPartialStrictEqual(val1, val2) {

lib/util.js

@@ -487,12 +487,11 @@ module.exports = {
   isArray: deprecate(ArrayIsArray,
                      'The `util.isArray` API is deprecated. Please use `Array.isArray()` instead.',
                      'DEP0044'),
-  isDeepStrictEqual(a, b) {
+  isDeepStrictEqual(a, b, options) {
     if (internalDeepEqual === undefined) {
-      internalDeepEqual = require('internal/util/comparisons')
-        .isDeepStrictEqual;
+      internalDeepEqual = require('internal/util/comparisons').isDeepStrictEqual;
     }
-    return internalDeepEqual(a, b);
+    return internalDeepEqual(a, b, options);
   },
   promisify,
   stripVTControlCharacters,

test/parallel/test-assert-class.js

@@ -478,3 +478,163 @@ test('Assert class non strict with simple diff', () => {
     );
   }
 });
+
+// Shared setup for skipPrototypeComparison tests
+{
+  const message = 'Expected values to be strictly deep-equal:\n' +
+  '+ actual - expected\n' +
+  '\n' +
+  '  [\n' +
+  '    1,\n' +
+  '    2,\n' +
+  '    3,\n' +
+  '    4,\n' +
+  '    5,\n' +
+  '+   6,\n' +
+  '-   9,\n' +
+  '    7\n' +
+  '  ]\n';
+
+  function CoolClass(name) { this.name = name; }
+
+  function AwesomeClass(name) { this.name = name; }
+
+  class Modern { constructor(value) { this.value = value; } }
+  class Legacy { constructor(value) { this.value = value; } }
+
+  const cool = new CoolClass('Assert is inspiring');
+  const awesome = new AwesomeClass('Assert is inspiring');
+  const modern = new Modern(42);
+  const legacy = new Legacy(42);
+
+  test('Assert class strict with skipPrototypeComparison', () => {
+    const assertInstance = new Assert({ skipPrototypeComparison: true });
+
+    assert.throws(
+      () => assertInstance.deepEqual([1, 2, 3, 4, 5, 6, 7], [1, 2, 3, 4, 5, 9, 7]),
+      { message }
+    );
+
+    assertInstance.deepEqual(cool, awesome);
+    assertInstance.deepStrictEqual(cool, awesome);
+    assertInstance.deepEqual(modern, legacy);
+    assertInstance.deepStrictEqual(modern, legacy);
+
+    const cool2 = new CoolClass('Soooo coooool');
+    assert.throws(
+      () => assertInstance.deepStrictEqual(cool, cool2),
+      { code: 'ERR_ASSERTION' }
+    );
+
+    const nested1 = { obj: new CoolClass('test'), arr: [1, 2, 3] };
+    const nested2 = { obj: new AwesomeClass('test'), arr: [1, 2, 3] };
+    assertInstance.deepStrictEqual(nested1, nested2);
+
+    const arr = new Uint8Array([1, 2, 3]);
+    const buf = Buffer.from([1, 2, 3]);
+    assertInstance.deepStrictEqual(arr, buf);
+  });
+
+  test('Assert class non strict with skipPrototypeComparison', () => {
+    const assertInstance = new Assert({ strict: false, skipPrototypeComparison: true });
+
+    assert.throws(
+      () => assertInstance.deepStrictEqual([1, 2, 3, 4, 5, 6, 7], [1, 2, 3, 4, 5, 9, 7]),
+      { message }
+    );
+
+    assertInstance.deepStrictEqual(cool, awesome);
+    assertInstance.deepStrictEqual(modern, legacy);
+  });
+
+  test('Assert class skipPrototypeComparison with complex objects', () => {
+    const assertInstance = new Assert({ skipPrototypeComparison: true });
+
+    function ComplexAwesomeClass(name, age) {
+      this.name = name;
+      this.age = age;
+      this.settings = {
+        theme: 'dark',
+        lang: 'en'
+      };
+    }
+
+    function ComplexCoolClass(name, age) {
+      this.name = name;
+      this.age = age;
+      this.settings = {
+        theme: 'dark',
+        lang: 'en'
+      };
+    }
+
+    const awesome1 = new ComplexAwesomeClass('Foo', 30);
+    const cool1 = new ComplexCoolClass('Foo', 30);
+
+    assertInstance.deepStrictEqual(awesome1, cool1);
+
+    const cool2 = new ComplexCoolClass('Foo', 30);
+    cool2.settings.theme = 'light';
+
+    assert.throws(
+      () => assertInstance.deepStrictEqual(awesome1, cool2),
+      { code: 'ERR_ASSERTION' }
+    );
+  });
+
+  test('Assert class skipPrototypeComparison with arrays and special objects', () => {
+    const assertInstance = new Assert({ skipPrototypeComparison: true });
+
+    const arr1 = [1, 2, 3];
+    const arr2 = new Array(1, 2, 3);
+    assertInstance.deepStrictEqual(arr1, arr2);
+
+    const date1 = new Date('2023-01-01');
+    const date2 = new Date('2023-01-01');
+    assertInstance.deepStrictEqual(date1, date2);
+
+    const regex1 = /test/g;
+    const regex2 = new RegExp('test', 'g');
+    assertInstance.deepStrictEqual(regex1, regex2);
+
+    const date3 = new Date('2023-01-02');
+    assert.throws(
+      () => assertInstance.deepStrictEqual(date1, date3),
+      { code: 'ERR_ASSERTION' }
+    );
+  });
+
+  test('Assert class skipPrototypeComparison with notDeepStrictEqual', () => {
+    const assertInstance = new Assert({ skipPrototypeComparison: true });
+
+    assert.throws(
+      () => assertInstance.notDeepStrictEqual(cool, awesome),
+      { code: 'ERR_ASSERTION' }
+    );
+
+    const notAwesome = new AwesomeClass('Not so awesome');
+    assertInstance.notDeepStrictEqual(cool, notAwesome);
+
+    const defaultAssertInstance = new Assert({ skipPrototypeComparison: false });
+    defaultAssertInstance.notDeepStrictEqual(cool, awesome);
+  });
+
+  test('Assert class skipPrototypeComparison with mixed types', () => {
+    const assertInstance = new Assert({ skipPrototypeComparison: true });
+
+    const obj1 = { value: 42, nested: { prop: 'test' } };
+
+    function CustomObj(value, nested) {
+      this.value = value;
+      this.nested = nested;
+    }
+
+    const obj2 = new CustomObj(42, { prop: 'test' });
+    assertInstance.deepStrictEqual(obj1, obj2);
+
+    assert.throws(
+      () => assertInstance.deepStrictEqual({ num: 42 }, { num: '42' }),
+      { code: 'ERR_ASSERTION' }
+    );
+  });
+}