Fix preserving object descriptors (#22)

Author: ehmicky

index.js

@@ -5,26 +5,17 @@ export function includeKeys(object, predicate) {
 		const set = new Set(predicate);
 		for (const key of Object.keys(object)) {
 			if (set.has(key)) {
-				const value = object[key];
-				Object.defineProperty(result, key, {
-					value,
-					writable: true,
-					enumerable: true,
-					configurable: true,
-				});
+				const descriptor = Object.getOwnPropertyDescriptor(object, key);
+				Object.defineProperty(result, key, descriptor);
 			}
 		}
 	} else {
 		// `for ... of Object.keys()` is faster than `for ... of Object.entries()`.
 		for (const key of Object.keys(object)) {
 			const value = object[key];
 			if (predicate(key, value, object)) {
-				Object.defineProperty(result, key, {
-					value,
-					writable: true,
-					enumerable: true,
-					configurable: true,
-				});
+				const descriptor = Object.getOwnPropertyDescriptor(object, key);
+				Object.defineProperty(result, key, descriptor);
 			}
 		}
 	}

test.js

@@ -33,6 +33,13 @@ test('includeKeys: non-enumerable properties are omitted', t => {
 	t.is(includeKeys(input, () => true).test, undefined);
 });
 
+test('includeKeys: descriptors are kept as is', t => {
+	const descriptor = {get() {}, set() {}, enumerable: true, configurable: false};
+	const input = Object.defineProperty({}, 'test', descriptor);
+	t.deepEqual(Object.getOwnPropertyDescriptor(includeKeys(input, () => true), 'test'), descriptor);
+	t.deepEqual(Object.getOwnPropertyDescriptor(includeKeys(input, ['test']), 'test'), descriptor);
+});
+
 test('includeKeys: inherited properties are omitted', t => {
 	const Parent = class {
 		test() {}
@@ -79,6 +86,13 @@ test('excludeKeys: non-enumerable properties are omitted', t => {
 	t.is(excludeKeys(input, () => false).test, undefined);
 });
 
+test('excludeKeys: descriptors are kept as is', t => {
+	const descriptor = {get() {}, set() {}, enumerable: true, configurable: false};
+	const input = Object.defineProperty({}, 'test', descriptor);
+	t.deepEqual(Object.getOwnPropertyDescriptor(excludeKeys(input, () => false), 'test'), descriptor);
+	t.deepEqual(Object.getOwnPropertyDescriptor(excludeKeys(input, []), 'test'), descriptor);
+});
+
 test('excludeKeys: inherited properties are omitted', t => {
 	const Parent = class {
 		test() {}