Implement Object.assign routine (#2678)

Related part of the standard: ECMA-262 v6, 19.1.2.1

JerryScript-DCO-1.0-Signed-off-by: Robert Fancsik frobert@inf.u-szeged.hu

tests/jerry/es2015/object-assign.js

@@ -0,0 +1,158 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+var object1 = {
+  a: 1,
+  b: 2,
+  c: 3
+};
+
+var object2 = Object.assign ({c: 4, d: 5}, object1);
+
+assert (JSON.stringify (object2) === '{"c":3,"d":5,"a":1,"b":2}');
+assert (object2.c === 3);
+assert (object2.d === 5);
+
+// Cloning an object
+var obj = { a: 1 };
+var copy = Object.assign ({}, obj);
+assert (JSON.stringify (copy) === '{"a":1}'); // { a: 1 }
+
+// Warning for Deep Clone
+function deepClone() {
+  'use strict';
+
+  var obj1 = { a: 0 , b: { c: 0}};
+  var obj2 = Object.assign ({}, obj1);
+  assert (JSON.stringify (obj2) === '{"a":0,"b":{"c":0}}');
+
+  obj1.a = 1;
+  assert (JSON.stringify (obj1) === '{"a":1,"b":{"c":0}}');
+  assert (JSON.stringify (obj2) === '{"a":0,"b":{"c":0}}');
+
+  obj2.a = 2;
+  assert (JSON.stringify (obj1) === '{"a":1,"b":{"c":0}}');
+  assert (JSON.stringify (obj2) === '{"a":2,"b":{"c":0}}');
+
+  obj2.b.c = 3;
+  assert (JSON.stringify (obj1) === '{"a":1,"b":{"c":3}}');
+  assert (JSON.stringify (obj2) === '{"a":2,"b":{"c":3}}');
+
+  // Deep Clone
+  obj1 = { a: 0 , b: { c: 0}};
+  var obj3 = JSON.parse (JSON.stringify (obj1));
+  obj1.a = 4;
+  obj1.b.c = 4;
+  assert (JSON.stringify (obj3) === '{"a":0,"b":{"c":0}}');
+}
+
+deepClone();
+
+// Merging objects
+var o1 = { a: 1 };
+var o2 = { b: 2 };
+var o3 = { c: 3 };
+
+var obj = Object.assign (o1, o2, o3);
+assert (JSON.stringify (obj) === '{"a":1,"b":2,"c":3}');
+assert (JSON.stringify (o1) === '{"a":1,"b":2,"c":3}');  //target object itself is changed.
+
+//Merging objects with same properties
+var o1 = { a: 1, b: 1, c: 1 };
+var o2 = { b: 2, c: 2 };
+var o3 = { c: 3 };
+
+var obj = Object.assign ({}, o1, o2, o3);
+assert (JSON.stringify (obj) === '{"a":1,"b":2,"c":3}');
+
+// Properties on the prototype chain and non-enumerable properties cannot be copied
+var obj = Object.create({ foo: 1 }, { // foo is on obj's prototype chain.
+  bar: {
+    value: 2  // bar is a non-enumerable property.
+  },
+  baz: {
+    value: 3,
+    enumerable: true  // baz is an own enumerable property.
+  }
+});
+
+var copy = Object.assign ({}, obj);
+assert (JSON.stringify (copy) === '{"baz":3}');
+
+// Primitives will be wrapped to objects
+var v1 = 'abc';
+var v2 = true;
+var v3 = 10;
+
+var obj = Object.assign ({}, v1, null, v2, undefined, v3);
+// Primitives will be wrapped, null and undefined will be ignored.
+// Note, only string wrappers can have own enumerable properties.
+assert (JSON.stringify (obj) === '{"0":"a","1":"b","2":"c"}');
+
+//Exceptions will interrupt the ongoing copying task
+var target = Object.defineProperty ({}, 'foo', {
+  value: 1,
+  writable: false
+}); // target.foo is a read-only property
+
+try {
+  // TypeError: "foo" is read-only,the Exception is thrown when assigning target.foo
+  Object.assign (target, { bar: 2 }, { foo2: 3, foo: 3, foo3: 3 }, { baz: 4 });
+  assert (false);
+} catch (e) {
+  assert (e instanceof TypeError);
+}
+
+assert (target.bar === 2);  // the first source was copied successfully.
+assert (target.foo2 === 3); // the first property of the second source was copied successfully.
+assert (target.foo === 1);  // exception is thrown here.
+assert (target.foo3 === undefined); // assign method has finished, foo3 will not be copied.
+assert (target.baz === undefined);  // the third source will not be copied either.
+
+// Copying accessors
+var obj = {
+  foo: 1,
+  get bar() {
+    return 2;
+  }
+};
+
+var copy = Object.assign ({}, obj);
+assert (JSON.stringify (copy) === '{"foo":1,"bar":2}');
+assert (copy.bar === 2); // the value of copy.bar is obj.bar's getter's return value.
+
+// This is an assign function that copies full descriptors
+function completeAssign (target, sources) {
+  sources.forEach (source => {
+    var descriptors = Object.keys (source).reduce ((descriptors, key) => {
+      descriptors[key] = Object.getOwnPropertyDescriptor (source, key);
+      return descriptors;
+    }, {});
+
+    Object.defineProperties (target, descriptors);
+  });
+  return target;
+}
+
+var copy = completeAssign ({}, [obj]);
+assert (JSON.stringify (copy) === '{"foo":1}');
+assert (copy.bar === 2);
+
+// Test when target is not coercible to object
+try {
+  Object.assign.call (undefined);
+  assert (false);
+} catch (e) {
+  assert (e instanceof TypeError)
+}