object-assign-plain.js

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// Tests for Object.assign's fast path for plain objects.

load(libdir + "asserts.js");

function testProtoSetter() {

    var from = Object.create(null);

    from.__proto__ = {};

    assertEq(Object.getPrototypeOf(from), null);

    var to = Object.assign({}, from);

    assertEq(Object.getPrototypeOf(to), from.__proto__);

    assertEq(Object.getOwnPropertyNames(to).length, 0);

testProtoSetter();

testProtoSetter();

testProtoSetter();

function testProtoDataProp() {

    var to = Object.create(null);

    to.__proto__ = 1;

    var from = Object.create(null);

    from.__proto__ = 2;

    Object.assign(to, from);

    assertEq(Object.getPrototypeOf(to), null);

    assertEq(to.__proto__, 2);

testProtoDataProp();

testProtoDataProp();

testProtoDataProp();

function testNonExtensible() {

    var to = Object.preventExtensions({x: 1});

    Object.assign(to, {x: 2});

    assertEq(to.x, 2);

    assertThrowsInstanceOf(() => Object.assign(to, {x: 3, y: 4}), TypeError);

    assertEq(to.x, 3);

    assertEq("y" in to, false);

testNonExtensible();

testNonExtensible();

testNonExtensible();

function testNonExtensibleNoProps() {

    var to = Object.preventExtensions({});

    Object.assign(to, {}); // No exception.

testNonExtensibleNoProps();

testNonExtensibleNoProps();

testNonExtensibleNoProps();

function testDenseElements() {

    var to = Object.assign({}, {0: 1, 1: 2});

    assertEq(to[0], 1);

    assertEq(to[1], 2);

testDenseElements();

testDenseElements();

testDenseElements();

function testNonWritableOnProto() {

    var proto = {};

    Object.defineProperty(proto, "x", {value: 1, enumerable: true, configurable: true});

    var to = Object.create(proto);

    assertThrowsInstanceOf(() => Object.assign(to, {x: 2}), TypeError);

    assertEq(to.x, 1);

    assertEq(Object.getOwnPropertyNames(to).length, 0);

testNonWritableOnProto();

testNonWritableOnProto();

testNonWritableOnProto();

function testAccessorOnProto() {

    var setterVal;

    var proto = {set a(v) { setterVal = v; }};

    var to = Object.assign(Object.create(proto), {a: 9});

    assertEq(setterVal, 9);

    assertEq(Object.getOwnPropertyNames(to).length, 0);

testAccessorOnProto();

testAccessorOnProto();

testAccessorOnProto();

function testSetAndAdd() {

    var to = Object.assign({x: 1, y: 2}, {x: 3, y: 4, z: 5});

    assertEq(to.x, 3);

    assertEq(to.y, 4);

    assertEq(to.z, 5);

testSetAndAdd();

testSetAndAdd();

testSetAndAdd();

function testNonConfigurableFrom() {

    var from = {};

    Object.defineProperty(from, "x", {value: 1, enumerable: true, writable: true});

    var to = Object.assign({}, from);

    assertEq(to.x, 1);

    assertEq(Object.getOwnPropertyDescriptor(to, "x").configurable, true);

testNonConfigurableFrom();

testNonConfigurableFrom();

testNonConfigurableFrom();

function testNonEnumerableFrom() {

    var from = {};

    Object.defineProperty(from, "x", {value: 1, configurable: true, writable: true});

    var to = Object.assign({}, from);

    assertEq(Object.getOwnPropertyNames(to).length, 0);

    assertEq(to.x, undefined);

testNonEnumerableFrom();

testNonEnumerableFrom();

testNonEnumerableFrom();

function testNonWritableFrom() {

    var from = {};

    Object.defineProperty(from, "x", {value: 1, configurable: true, enumerable: true});

    var to = Object.assign({}, from);

    assertEq(to.x, 1);

    assertEq(Object.getOwnPropertyDescriptor(to, "x").writable, true);

testNonWritableFrom();

testNonWritableFrom();

testNonWritableFrom();

function testFrozenProto() {

    var proto = Object.freeze({x: 1});

    var target = Object.create(proto);

    Object.assign(target, {foo: 1});

    assertEq(target.foo, 1);

    assertThrowsInstanceOf(() => Object.assign(target, {x: 2}), TypeError);

    assertEq(target.x, 1);

testFrozenProto();

testFrozenProto();

testFrozenProto();

function testReuseShape() {

    var from = {};

    from.x = 1;

    from.y = 2;

    var to = Object.assign({}, from);

    assertEq(to.x, 1);

    assertEq(to.y, 2);

testReuseShape();

testReuseShape();

testReuseShape();