[es6] implement Object.assign

test/mjsunit/harmony/object-assign.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-object
+
+// Based on Mozilla Array.of() tests at http://dxr.mozilla.org/mozilla-central/source/js/src/tests/ecma_6/Object/assign.js

[arv (Not doing code reviews), 2015/04/03 21:15:09]

Is this comment really correct?

[caitp (gmail), 2015/04/03 21:28:41]

The Array.of() part certainly isn't! fixing that

+
+function checkDataProperty(object, propertyKey, value, writable, enumerable, configurable) {
+  var desc = Object.getOwnPropertyDescriptor(object, propertyKey);
+  assertFalse(desc === undefined);
+  assertTrue('value' in desc);
+  assertEquals(desc.value, value);
+  assertEquals(desc.writable, writable);
+  assertEquals(desc.enumerable, enumerable);
+  assertEquals(desc.configurable, configurable);
+}
+
+// 19.1.2.1 Object.assign ( target, ...sources )
+assertEquals(Object.assign.length, 2);
+
+// Basic functionality works with multiple sources
+(function basicMultipleSources() {
+  var a = {};
+  var b = { bProp: 1 };
+  var c = { cProp: 2 };
+  Object.assign(a, b, c);
+  assertEquals(a, {
+    bProp: 1,
+    cProp: 2
+  });
+})();
+
+// Basic functionality works with symbols
+(function basicSymbols() {
+  var a = {};
+  var b = { bProp: 1 };
+  var aSymbol = Symbol("aSymbol");
+  b[aSymbol] = 2;
+  Object.assign(a, b);
+  assertEquals(1, a.bProp);
+  assertEquals(2, a[aSymbol]);
+})();
+
+// Dies if target is null or undefined
+assertThrows(function() { return Object.assign(null, null); }, TypeError);
+assertThrows(function() { return Object.assign(null, {}); }, TypeError);
+assertThrows(function() { return Object.assign(undefined); }, TypeError);
+assertThrows(function() { return Object.assign(); }, TypeError);
+
+// Calls ToObject for target
+assertTrue(Object.assign(true, {}) instanceof Boolean);
+assertTrue(Object.assign(1, {}) instanceof Number);
+assertTrue(Object.assign("string", {}) instanceof String);
+var o = {};
+assertSame(Object.assign(o, {}), o);
+
+// Only [[Enumerable]] properties are assigned to target
+(function onlyEnumerablePropertiesAssigned() {
+  var source = Object.defineProperties({}, {
+    a: {value: 1, enumerable: true},
+    b: {value: 2, enumerable: false},
+  });
+  var target = Object.assign({}, source);
+  assertTrue("a" in target);
+  assertFalse("b" in target);
+})();
+
+// Properties are retrieved through Get()
+// Properties are assigned through Put()
+(function testPropertiesAssignedThroughPut() {
+  var setterCalled = false;
+  Object.assign({set a(v) { setterCalled = v }}, {a: true});
+  assertTrue(setterCalled);
+})();
+
+// Properties are retrieved through Get()
+// Properties are assigned through Put(): Existing property attributes are not altered
+(function propertiesAssignedExistingNotAltered() {
+  var source = {a: 1, b: 2, c: 3};
+  var target = {a: 0, b: 0, c: 0};
+  Object.defineProperty(target, "a", {enumerable: false});
+  Object.defineProperty(target, "b", {configurable: false});
+  Object.defineProperty(target, "c", {enumerable: false, configurable: false});
+  Object.assign(target, source);
+  checkDataProperty(target, "a", 1, true, false, true);
+  checkDataProperty(target, "b", 2, true, true, false);
+  checkDataProperty(target, "c", 3, true, false, false);
+})();
+
+// Properties are retrieved through Get()
+// Properties are assigned through Put(): Throws TypeError if non-writable
+(function propertiesAssignedTypeErrorNonWritable() {
+  var source = {a: 1};
+  var target = {a: 0};
+  Object.defineProperty(target, "a", {writable: false});
+  assertThrows(function() { return Object.assign(target, source); }, TypeError);
+  checkDataProperty(target, "a", 0, false, true, true);
+})();
+
+// Properties are retrieved through Get()
+// Put() creates standard properties; Property attributes from source are
+// ignored
+(function createsStandardProperties() {
+  var source = {a: 1, b: 2, c: 3, get d() { return 4 }};
+  Object.defineProperty(source, "b", {writable: false});
+  Object.defineProperty(source, "c", {configurable: false});
+  var target = Object.assign({}, source);
+  checkDataProperty(target, "a", 1, true, true, true);
+  checkDataProperty(target, "b", 2, true, true, true);
+  checkDataProperty(target, "c", 3, true, true, true);
+  checkDataProperty(target, "d", 4, true, true, true);
+})();
+
+// Properties created during traversal are not copied
+(function propertiesCreatedDuringTraversalNotCopied() {
+  var source = {get a() { this.b = 2 }};
+  var target = Object.assign({}, source);
+  assertTrue("a" in target);
+  assertFalse("b" in target);
+})();
+
+// String and Symbol valued properties are copied
+(function testStringAndSymbolPropertiesCopied() {
+  var keyA = "str-prop";
+  var source = {"str-prop": 1};
+  var target = Object.assign({}, source);
+  checkDataProperty(target, keyA, 1, true, true, true);
+})();
+
+(function testExceptionsStopFirstException() {
+  var ErrorA = function ErrorA() {};
+  var ErrorB = function ErrorB() {};
+  var log = "";
+  var source = { b: 1, a: 1 };
+  var target = {
+      set a(v) { log += "a"; throw new ErrorA },
+      set b(v) { log += "b"; throw new ErrorB },
+  };
+  assertThrows(function() { return Object.assign(target, source); }, ErrorB);
+  assertEquals(log, "b");
+})();