[es6] implement destructuring assignment

test/mjsunit/harmony/destructuring-assignment.js

+// Copyright 2015 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-destructuring-assignment --harmony-destructuring-bind
+
+// script-level tests
+var ox, oy = {}, oz;
+({
+  x: ox,
+  y: oy.value,
+  y2: oy["value2"],
+  z: ({ set v(val) { oz = val; } }).v
+} = {
+  x: "value of x",
+  y: "value of y1",
+  y2: "value of y2",
+  z: "value of z"
+});
+assertEquals("value of x", ox);
+assertEquals("value of y1", oy.value);
+assertEquals("value of y2", oy.value2);
+assertEquals("value of z", oz);
+
+[ox, oy.value, oy["value2"], ...{ set v(val) { oz = val; } }.v] = [
+  1007,
+  798432,
+  555,
+  1, 2, 3, 4, 5
+];
+assertEquals(ox, 1007);
+assertEquals(oy.value, 798432);
+assertEquals(oy.value2, 555);
+assertEquals(oz, [1, 2, 3, 4, 5]);
+
+
+(function testInFunction() {
+  var x, y = {}, z;
+  ({
+    x: x,
+    y: y.value,
+    y2: y["value2"],
+    z: ({ set v(val) { z = val; } }).v
+  } = {
+    x: "value of x",
+    y: "value of y1",
+    y2: "value of y2",
+    z: "value of z"
+  });
+  assertEquals("value of x", x);
+  assertEquals("value of y1", y.value);
+  assertEquals("value of y2", y.value2);
+  assertEquals("value of z", z);
+
+  [x, y.value, y["value2"], ...{ set v(val) { z = val; } }.v] = [
+    1007,
+    798432,
+    555,
+    1, 2, 3, 4, 5
+  ];
+  assertEquals(x, 1007);
+  assertEquals(y.value, 798432);
+  assertEquals(y.value2, 555);
+  assertEquals(z, [1, 2, 3, 4, 5]);
+})();
+
+
+(function testArrowFunctionInitializers() {
+  var fn = (config = {
+    value: defaults.value,
+    nada: { nada: defaults.nada } = { nada: "nothing" }
+  } = { value: "BLAH" }) => config;
+  var defaults = {};
+  assertEquals({ value: "BLAH" }, fn());
+  assertEquals("BLAH", defaults.value);
+  assertEquals("nothing", defaults.nada);
+})();
+
+
+(function testArrowFunctionInitializers2() {
+  var fn = (config = [
+    defaults.value,
+    { nada: defaults.nada } = { nada: "nothing" }
+  ] = ["BLAH"]) => config;
+  var defaults = {};
+  assertEquals(["BLAH"], fn());
+  assertEquals("BLAH", defaults.value);
+  assertEquals("nothing", defaults.nada);
+})();
+
+
+(function testFunctionInitializers() {
+  function fn(config = {
+    value: defaults.value,
+    nada: { nada: defaults.nada } = { nada: "nothing" }
+  } = { value: "BLAH" }) {
+    return config;
+  }
+  var defaults = {};
+  assertEquals({ value: "BLAH" }, fn());
+  assertEquals("BLAH", defaults.value);
+  assertEquals("nothing", defaults.nada);
+})();
+
+
+(function testFunctionInitializers2() {
+  function fn(config = [
+    defaults.value,
+    { nada: defaults.nada } = { nada: "nothing" }
+  ] = ["BLAH"]) { return config; }
+  var defaults = {};
+  assertEquals(["BLAH"], fn());
+  assertEquals("BLAH", defaults.value);
+  assertEquals("nothing", defaults.nada);
+})();
+
+
+(function testDeclarationInitializers() {
+  var defaults = {};
+  var { value } = { value: defaults.value } = { value: "BLAH" };
+  assertEquals("BLAH", value);
+  assertEquals("BLAH", defaults.value);
+})();
+
+
+(function testDeclarationInitializers2() {
+  var defaults = {};
+  var [value] = [defaults.value] = ["BLAH"];
+  assertEquals("BLAH", value);
+  assertEquals("BLAH", defaults.value);
+})();
+
+
+(function testObjectLiteralProperty() {
+  var ext = {};
+  var obj = {
+    a: { b: ext.b, c: ext["c"], d: { set v(val) { ext.d = val; } }.v } = {
+      b: "b", c: "c", d: "d" }
+  };
+  assertEquals({ b: "b", c: "c", d: "d" }, ext);
+  assertEquals({ a: { b: "b", c: "c", d: "d" } }, obj);
+})();
+
+
+(function testArrayLiteralProperty() {
+  var ext = {};
+  var obj = [
+    ...[ ext.b, ext["c"], { set v(val) { ext.d = val; } }.v ] = [
+      "b", "c", "d" ]
+  ];
+  assertEquals({ b: "b", c: "c", d: "d" }, ext);
+  assertEquals([ "b", "c", "d" ], obj);
+})();
+
+
+// TODO(caitp): add similar test for ArrayPatterns, once Proxies support
+// delegating symbol-keyed get/set.
+(function testObjectPatternOperationOrder() {
+  var steps = [];
+  var store = {};
+  function computePropertyName(name) {
+    steps.push("compute name: " + name);
+    return name;
+  }
+  function loadValue(descr, value) {
+    steps.push("load: " + descr + " > " + value);
+    return value;
+  }
+  function storeValue(descr, name, value) {
+    steps.push("store: " + descr + " = " + value);
+    store[name] = value;
+  }
+  var result = {
+    get a() { assertUnreachable(); },
+    set a(value) { storeValue("result.a", "a", value); },
+    get b() { assertUnreachable(); },
+    set b(value) { storeValue("result.b", "b", value); }
+  };
+
+  ({
+    obj: {
+      x: result.a = 10,
+      [computePropertyName("y")]: result.b = false,
+    } = {}
+  } = { obj: {
+    get x() { return loadValue(".temp.obj.x", undefined); },
+    set x(value) { assertUnreachable(); },
+    get y() { return loadValue(".temp.obj.y", undefined); },
+    set y(value) { assertUnreachable(); }
+  }});
+
+  assertPropertiesEqual({
+    a: 10,
+    b: false
+  }, store);
+
+  assertArrayEquals([
+    "load: .temp.obj.x > undefined",
+    "store: result.a = 10",
+
+    "compute name: y",
+    "load: .temp.obj.y > undefined",
+    "store: result.b = false"
+  ], steps);
+
+  steps = [];
+
+  ({
+    obj: {
+      x: result.a = 50,
+      [computePropertyName("y")]: result.b = "hello",
+    } = {}
+  } = { obj: {
+    get x() { return loadValue(".temp.obj.x", 20); },
+    set x(value) { assertUnreachable(); },
+    get y() { return loadValue(".temp.obj.y", true); },
+    set y(value) { assertUnreachable(); }
+  }});
+
+  assertPropertiesEqual({
+    a: 20,
+    b: true
+  }, store);
+
+  assertArrayEquals([
+    "load: .temp.obj.x > 20",
+    "store: result.a = 20",
+    "compute name: y",
+    "load: .temp.obj.y > true",
+    "store: result.b = true",
+  ], steps);
+})();
+
+// Credit to Mike Pennisi and other Test262 contributors for originally writing
+// the testse the following are based on.
+(function testArrayElision() {
+  var value = [1, 2, 3, 4, 5, 6, 7, 8, 9];
+  var a, obj = {};
+  var result = [, a, , obj.b, , ...obj["rest"]] = value;
+
+  assertEquals(result, value);
+  assertEquals(2, a);
+  assertEquals(4, obj.b);
+  assertArrayEquals([6, 7, 8, 9], obj.rest);
+})();
+
+(function testArrayElementInitializer() {
+  function test(value, initializer, expected) {
+    var a, obj = {};
+    var initialized = false;
+    var shouldBeInitialized = value[0] === undefined;
+    assertEquals(value, [ a = (initialized = true, initializer) ] = value);
+    assertEquals(expected, a);
+    assertEquals(shouldBeInitialized, initialized);
+
+    var initialized2 = false;
+    assertEquals(value, [ obj.a = (initialized2 = true, initializer) ] = value);
+    assertEquals(expected, obj.a);
+    assertEquals(shouldBeInitialized, initialized2);
+  }
+
+  test([], "BAM!", "BAM!");
+  test([], "BOOP!", "BOOP!");
+  test([null], 123, null);
+  test([undefined], 456, 456);
+  test([,], "PUPPIES", "PUPPIES");
+
+  (function accept_IN() {
+    var value = [], x;
+    assertEquals(value, [ x = 'x' in {} ] = value);
+    assertEquals(false, x);
+  })();
+
+  (function ordering() {
+    var x = 0, a, b, value = [];
+    assertEquals(value, [ a = x += 1, b = x *= 2 ] = value);
+    assertEquals(1, a);
+    assertEquals(2, b);
+    assertEquals(2, x);
+  })();
+
+  (function yieldExpression() {
+    var value = [], it, result, x;
+    it = (function*() {
+      result = [ x = yield ] = value;
+    })();
+    var next = it.next();
+
+    assertEquals(undefined, result);
+    assertEquals(undefined, next.value);
+    assertEquals(false, next.done);
+    assertEquals(undefined, x);
+
+    next = it.next(86);
+
+    assertEquals(value, result);
+    assertEquals(undefined, next.value);
+    assertEquals(true, next.done);
+    assertEquals(86, x);
+  })();
+
+  (function yieldIdentifier() {
+    var value = [], yield = "BOOP!", x;
+    assertEquals(value, [ x = yield ] = value);
+    assertEquals("BOOP!", x);
+  })();
+
+  assertThrows(function let_TDZ() {
+    "use strict";
+    var x;
+    [ x = y ] = [];
+    let y;
+  }, ReferenceError);
+})();
+
+
+(function testArrayElementNestedPattern() {
+  assertThrows(function nestedArrayRequireObjectCoercibleNull() {
+    var x; [ [ x ] ] = [ null ];
+  }, TypeError);
+
+  assertThrows(function nestedArrayRequireObjectCoercibleUndefined() {
+    var x; [ [ x ] ] = [ undefined ];
+  }, TypeError);
+
+  assertThrows(function nestedArrayRequireObjectCoercibleUndefined2() {
+    var x; [ [ x ] ] = [ ];
+  }, TypeError);
+
+  assertThrows(function nestedArrayRequireObjectCoercibleUndefined3() {
+    var x; [ [ x ] ] = [ , ];
+  }, TypeError);
+
+  assertThrows(function nestedObjectRequireObjectCoercibleNull() {
+    var x; [ { x } ] = [ null ];
+  }, TypeError);
+
+  assertThrows(function nestedObjectRequireObjectCoercibleUndefined() {
+    var x; [ { x } ] = [ undefined ];
+  }, TypeError);
+
+  assertThrows(function nestedObjectRequireObjectCoercibleUndefined2() {
+    var x; [ { x } ] = [ ];
+  }, TypeError);
+
+  assertThrows(function nestedObjectRequireObjectCoercibleUndefined3() {
+    var x; [ { x } ] = [ , ];
+  }, TypeError);
+
+  (function nestedArray() {
+    var x, value = [ [ "zap", "blonk" ] ];
+    assertEquals(value, [ [ , x ] ] = value);
+    assertEquals("blonk", x);
+  })();
+
+  (function nestedObject() {
+    var x, value = [ { a: "zap", b: "blonk" } ];
+    assertEquals(value, [ { b: x } ] = value);
+    assertEquals("blonk", x);
+  })();
+})();
+
+(function testArrayRestElement() {
+  (function testBasic() {
+    var x, rest, array = [1, 2, 3];
+    assertEquals(array, [x, ...rest] = array);
+    assertEquals(1, x);
+    assertEquals([2, 3], rest);
+
+    array = [4, 5, 6];
+    assertEquals(array, [, ...rest] = array);
+    assertEquals([5, 6], rest);
+
+  })();
+
+  (function testNestedRestObject() {
+    var value = [1, 2, 3], x;
+    assertEquals(value, [...{ 1: x }] = value);
+    assertEquals(2, x);
+  })();
+
+  (function iterable() {
+    var count = 0;
+    var x, y, z;
+    function* g() {
+      count++;
+      yield;
+      count++;
+      yield;
+      count++;
+      yield;
+    }
+    var it = g();
+    assertEquals(it, [...x] = it);
+    assertEquals([undefined, undefined, undefined], x);
+    assertEquals(3, count);
+
+    it = [g()];
+    assertEquals(it, [ [...y] ] = it);
+    assertEquals([undefined, undefined, undefined], y);
+    assertEquals(6, count);
+
+    it = { a: g() };
+    assertEquals(it, { a: [...z] } = it);
+    assertEquals([undefined, undefined, undefined], z);
+    assertEquals(9, count);
+  })();
+})();
+
+(function testRequireObjectCoercible() {
+  assertThrows(() => ({} = undefined), TypeError);
+  assertThrows(() => ({} = null), TypeError);
+  assertThrows(() => [] = undefined, TypeError);
+  assertThrows(() => [] = null, TypeError);
+  assertEquals("test", ({} = "test"));
+  assertEquals("test", [] = "test");
+  assertEquals(123, ({} = 123));
+})();
+
+(function testConstReassignment() {
+  "use strict";
+  const c = "untouchable";
+  assertThrows(() => { [ c ] = [ "nope!" ]; }, TypeError);
+  assertThrows(() => { [ [ c ] ]  = [ [ "nope!" ] ]; }, TypeError);
+  assertThrows(() => { [ { c } ]  = [ { c: "nope!" } ]; }, TypeError);
+  assertThrows(() => { ({ c } = { c: "nope!" }); }, TypeError);
+  assertThrows(() => { ({ a: { c } } = { a: { c: "nope!" } }); }, TypeError);
+  assertThrows(() => { ({ a: [ c ] } = { a: [ "nope!" ] }); }, TypeError);
+  assertEquals("untouchable", c);
+})();