util: add kEmptyObject to internal/util

PR-URL: #43159
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>

lib/internal/util.js

@@ -13,6 +13,7 @@ const {
   ObjectGetOwnPropertyDescriptor,
   ObjectGetOwnPropertyDescriptors,
   ObjectGetPrototypeOf,
+  ObjectFreeze,
   ObjectSetPrototypeOf,
   Promise,
   ReflectApply,
@@ -504,6 +505,8 @@ const lazyDOMException = hideStackFrames((message, name) => {
 const kEnumerableProperty = ObjectCreate(null);
 kEnumerableProperty.enumerable = true;
 
+const kEmptyObject = ObjectFreeze(ObjectCreate(null));
+
 module.exports = {
   assertCrypto,
   cachedResult,
@@ -544,5 +547,6 @@ module.exports = {
   kIsEncodingSymbol: Symbol('kIsEncodingSymbol'),
   kVmBreakFirstLineSymbol: Symbol('kVmBreakFirstLineSymbol'),
 
+  kEmptyObject,
   kEnumerableProperty,
 };

test/parallel/test-internal-util-objects.js

@@ -0,0 +1,90 @@
+// Flags: --expose-internals
+'use strict';
+require('../common');
+
+// Test helper objects from internal/util
+
+const assert = require('assert');
+const {
+  kEnumerableProperty,
+  kEmptyObject,
+} = require('internal/util');
+
+Object.prototype.blep = 'blop';
+
+{
+  assert.strictEqual(
+    kEnumerableProperty.blep,
+    undefined
+  );
+  assert.strictEqual(
+    kEnumerableProperty.enumerable,
+    true
+  );
+  assert.strictEqual(
+    Object.getPrototypeOf(kEnumerableProperty),
+    null
+  );
+  assert.deepStrictEqual(
+    Object.getOwnPropertyNames(kEnumerableProperty),
+    [ 'enumerable' ]
+  );
+}
+
+{
+  assert.strictEqual(
+    kEmptyObject.blep,
+    undefined
+  );
+  assert.strictEqual(
+    kEmptyObject.prototype,
+    undefined
+  );
+  assert.strictEqual(
+    Object.getPrototypeOf(kEmptyObject),
+    null
+  );
+  assert.strictEqual(
+    kEmptyObject instanceof Object,
+    false
+  );
+  assert.deepStrictEqual(
+    Object.getOwnPropertyDescriptors(kEmptyObject),
+    {}
+  );
+  assert.deepStrictEqual(
+    Object.getOwnPropertyNames(kEmptyObject),
+    []
+  );
+  assert.deepStrictEqual(
+    Object.getOwnPropertySymbols(kEmptyObject),
+    []
+  );
+  assert.strictEqual(
+    Object.isExtensible(kEmptyObject),
+    false
+  );
+  assert.strictEqual(
+    Object.isSealed(kEmptyObject),
+    true
+  );
+  assert.strictEqual(
+    Object.isFrozen(kEmptyObject),
+    true
+  );
+
+  assert.throws(
+    () => kEmptyObject.foo = 'bar',
+    TypeError
+  );
+  assert.throws(
+    () => Object.assign(kEmptyObject, { foo: 'bar' }),
+    TypeError
+  );
+  assert.throws(
+    () => Object.defineProperty(kEmptyObject, 'foo', {}),
+    TypeError
+  );
+}
+
+delete Object.prototype.blep;