Implement ES6 @@isConcatSpreadable

test/mjsunit/harmony/array-concat.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-arrays --harmony-classes
+
+(function testArrayConcatArity() {
+  "use strict";
+  assertEquals(1, Array.prototype.concat.length);
+})();
+
+
+(function testArrayConcatNoPrototype() {
+  "use strict";
+  assertEquals(void 0, Array.prototype.concat.prototype);
+})();
+
+
+(function testArrayConcatDescriptor() {
+  "use strict";
+  var desc = Object.getOwnPropertyDescriptor(Array.prototype, 'concat');
+  assertEquals(false, desc.enumerable);
+})();
+
+
+(function testConcatArrayLike() {
+  "use strict";
+  var obj = {
+    "length": 6,
+    "1": "A",
+    "3": "B",
+    "5": "C"
+  };
+  obj[Symbol.isConcatSpreadable] = true;
+  var obj2 = { length: 3, "0": "0", "1": "1", "2": "2" };
+  var arr = ["X", "Y", "Z"];
+  assertEquals([void 0, "A", void 0, "B", void 0, "C",
+               { "length": 3, "0": "0", "1": "1", "2": "2" },
+               "X", "Y", "Z"], Array.prototype.concat.call(obj, obj2, arr));
+})();
+
+
+(function testConcatHoleyArray() {
+  "use strict";
+  var arr = [];
+  arr[4] = "Item 4";
+  arr[8] = "Item 8";
+  var arr2 = [".", "!", "?"];
+  assertEquals([void 0, void 0, void 0, void 0, "Item 4", void 0, void 0,
+                void 0, "Item 8", ".", "!", "?"], arr.concat(arr2));
+})();
+
+
+(function testIsConcatSpreadableGetterThrows() {
+  "use strict";
+  function MyError() {}
+  var obj = {};
+  Object.defineProperty(obj, Symbol.isConcatSpreadable, {
+    get: function() { throw new MyError(); }
+  });
+
+  assertThrows(function() {
+    [].concat(obj);
+  }, MyError);
+
+  assertThrows(function() {
+    Array.prototype.concat.call(obj, 1, 2, 3);
+  }, MyError);
+})();
+
+
+(function testConcatLengthThrows() {
+  "use strict";
+  function MyError() {}
+  var obj = {};
+  obj[Symbol.isConcatSpreadable] = true;
+  Object.defineProperty(obj, "length", {
+    get: function() { throw new MyError(); }
+  });
+
+  assertThrows(function() {
+    [].concat(obj);
+  }, MyError);
+
+  assertThrows(function() {
+    Array.prototype.concat.call(obj, 1, 2, 3);
+  }, MyError);
+})();
+
+
+(function testConcatArraySubclass() {
+  "use strict";
+  // TODO(caitp): when concat is called on instances of classes which extend
+  // Array, they should:
+  //
+  // - return an instance of the class, rather than an Array instance (if from
+  //   same Realm)
+  // - always treat such classes as concat-spreadable
+})();
+
+
+(function testConcatNonArray() {
+  "use strict";
+  class NonArray {
+    constructor() { Array.apply(this, arguments); }
+  };
+
+  var obj = new NonArray(1,2,3);
+  var result = Array.prototype.concat.call(obj, 4, 5, 6);
+  assertEquals(Array, result.constructor);
+  assertEquals([obj,4,5,6], result);
+  assertFalse(result instanceof NonArray);
+})();
+
+
+function testConcatTypedArray(type, elems, modulo) {
+  "use strict";
+  var items = new Array(elems);
+  for (var i = 0; i < elems; ++i) {
+    items[i] = modulo === false ? i : elems % modulo;
+  }
+  var ta = new type(items);
+  assertEquals([ta, ta], [].concat(ta, ta));
+  ta[Symbol.isConcatSpreadable] = true;
+  assertEquals(items, [].concat(ta));
+}
+
+(function testConcatSmallTypedArray() {
+  var max = [2^8, 2^16, 2^32, false, false];
+  [
+    Uint8Array,
+    Uint16Array,
+    Uint32Array,
+    Float32Array,
+    Float64Array
+  ].forEach(function(ctor, i) {
+    testConcatTypedArray(ctor, 2, max[i]);
+  });
+})();
+
+
+(function testConcatLargeTypedArray() {
+  var max = [2^8, 2^16, 2^32, false, false];
+  [
+    Uint8Array,
+    Uint16Array,
+    Uint32Array,
+    Float32Array,
+    Float64Array
+  ].forEach(function(ctor, i) {
+    testConcatTypedArray(ctor, 4000, max[i]);
+  });
+})();
+
+
+(function testConcatStrictArguments() {
+  var args = (function() { "use strict"; return arguments; })(1,2,3);
+  args[Symbol.isConcatSpreadable] = true;
+  assertEquals([1, 2, 3, 1, 2, 3], [].concat(args, args));
+})();
+
+
+(function testConcatSloppyArguments() {
+  var args = (function() { return arguments; })(1,2,3);

[Dmitry Lomov (no reviews), 2014/12/11 11:05:47]

Yes, this test does not produce SLOPPY_ARGUMENTS_ELEMENT_KIND.
You need a function to have both arguments and parameters to get it.
So just replace `function f()` with `function f(x, y, z)`
The logic that governs this is here:
https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/runtime/run...

[caitp (gmail), 2014/12/11 13:09:35]

Okay --- I've added a handler for SLOPPY_ARGUMENTS_ELEMENTS, but did not remove
the default case --- It's a simple thing to remove it, but I think it's good to
have missing cases stand out more than just not adding the elements.

Also added some tests with different variations of the sloppy arguments object

[Dmitry Lomov (no reviews), 2014/12/11 14:01:50]

No, please remove the default case, so that compiler complains if we add a new
ElementsKind and it goes unhandled here. 

[caitp (gmail), 2014/12/11 14:41:17]

Done --- There were a bunch of missing cases, I'm not sure exactly how to test
all of those though. The TypedArray tests don't hit them, as far as I can see

+  args[Symbol.isConcatSpreadable] = true;
+  assertEquals([1, 2, 3, 1, 2, 3], [].concat(args, args));
+})();
+
+
+// ES5 tests
+(function testArrayConcatES5() {
+  "use strict";
+  var poses;
+  var pos;
+
+  poses = [140, 4000000000];
+  while (pos = poses.shift()) {
+    var a = new Array(pos);
+    var array_proto = [];
+    a.__proto__ = array_proto;
+    assertEquals(pos, a.length);
+    a.push('foo');
+    assertEquals(pos + 1, a.length);
+    var b = ['bar'];
+    var c = a.concat(b);
+    assertEquals(pos + 2, c.length);
+    assertEquals("undefined", typeof(c[pos - 1]));
+    assertEquals("foo", c[pos]);
+    assertEquals("bar", c[pos + 1]);
+
+    // Can we fool the system by putting a number in a string?
+    var onetwofour = "124";
+    a[onetwofour] = 'doo';
+    assertEquals(a[124], 'doo');
+    c = a.concat(b);
+    assertEquals(c[124], 'doo');
+
+    // If we put a number in the prototype, then the spec says it should be
+    // copied on concat.
+    array_proto["123"] = 'baz';
+    assertEquals(a[123], 'baz');
+
+    c = a.concat(b);
+    assertEquals(pos + 2, c.length);
+    assertEquals("baz", c[123]);
+    assertEquals("undefined", typeof(c[pos - 1]));
+    assertEquals("foo", c[pos]);
+    assertEquals("bar", c[pos + 1]);
+
+    // When we take the number off the prototype it disappears from a, but
+    // the concat put it in c itself.
+    array_proto["123"] = undefined;
+    assertEquals("undefined", typeof(a[123]));
+    assertEquals("baz", c[123]);
+
+    // If the element of prototype is shadowed, the element on the instance
+    // should be copied, but not the one on the prototype.
+    array_proto[123] = 'baz';
+    a[123] = 'xyz';
+    assertEquals('xyz', a[123]);
+    c = a.concat(b);
+    assertEquals('xyz', c[123]);
+
+    // Non-numeric properties on the prototype or the array shouldn't get
+    // copied.
+    array_proto.moe = 'joe';
+    a.ben = 'jerry';
+    assertEquals(a["moe"], 'joe');
+    assertEquals(a["ben"], 'jerry');
+    c = a.concat(b);
+    // ben was not copied
+    assertEquals("undefined", typeof(c.ben));
+
+    // When we take moe off the prototype it disappears from all arrays.
+    array_proto.moe = undefined;
+    assertEquals("undefined", typeof(c.moe));
+
+    // Negative indices don't get concated.
+    a[-1] = 'minus1';
+    assertEquals("minus1", a[-1]);
+    assertEquals("undefined", typeof(a[0xffffffff]));
+    c = a.concat(b);
+    assertEquals("undefined", typeof(c[-1]));
+    assertEquals("undefined", typeof(c[0xffffffff]));
+    assertEquals(c.length, a.length + 1);
+  }
+
+  poses = [140, 4000000000];
+  while (pos = poses.shift()) {
+    var a = new Array(pos);
+    assertEquals(pos, a.length);
+    a.push('foo');
+    assertEquals(pos + 1, a.length);
+    var b = ['bar'];
+    var c = a.concat(b);
+    assertEquals(pos + 2, c.length);
+    assertEquals("undefined", typeof(c[pos - 1]));
+    assertEquals("foo", c[pos]);
+    assertEquals("bar", c[pos + 1]);
+
+    // Can we fool the system by putting a number in a string?
+    var onetwofour = "124";
+    a[onetwofour] = 'doo';
+    assertEquals(a[124], 'doo');
+    c = a.concat(b);
+    assertEquals(c[124], 'doo');
+
+    // If we put a number in the prototype, then the spec says it should be
+    // copied on concat.
+    Array.prototype["123"] = 'baz';
+    assertEquals(a[123], 'baz');
+
+    c = a.concat(b);
+    assertEquals(pos + 2, c.length);
+    assertEquals("baz", c[123]);
+    assertEquals("undefined", typeof(c[pos - 1]));
+    assertEquals("foo", c[pos]);
+    assertEquals("bar", c[pos + 1]);
+
+    // When we take the number off the prototype it disappears from a, but
+    // the concat put it in c itself.
+    Array.prototype["123"] = undefined;
+    assertEquals("undefined", typeof(a[123]));
+    assertEquals("baz", c[123]);
+
+    // If the element of prototype is shadowed, the element on the instance
+    // should be copied, but not the one on the prototype.
+    Array.prototype[123] = 'baz';
+    a[123] = 'xyz';
+    assertEquals('xyz', a[123]);
+    c = a.concat(b);
+    assertEquals('xyz', c[123]);
+
+    // Non-numeric properties on the prototype or the array shouldn't get
+    // copied.
+    Array.prototype.moe = 'joe';
+    a.ben = 'jerry';
+    assertEquals(a["moe"], 'joe');
+    assertEquals(a["ben"], 'jerry');
+    c = a.concat(b);
+    // ben was not copied
+    assertEquals("undefined", typeof(c.ben));
+    // moe was not copied, but we can see it through the prototype
+    assertEquals("joe", c.moe);
+
+    // When we take moe off the prototype it disappears from all arrays.
+    Array.prototype.moe = undefined;
+    assertEquals("undefined", typeof(c.moe));
+
+    // Negative indices don't get concated.
+    a[-1] = 'minus1';
+    assertEquals("minus1", a[-1]);
+    assertEquals("undefined", typeof(a[0xffffffff]));
+    c = a.concat(b);
+    assertEquals("undefined", typeof(c[-1]));
+    assertEquals("undefined", typeof(c[0xffffffff]));
+    assertEquals(c.length, a.length + 1);
+
+  }
+
+  a = [];
+  c = a.concat('Hello');
+  assertEquals(1, c.length);
+  assertEquals("Hello", c[0]);
+  assertEquals("Hello", c.toString());
+
+  // Check that concat preserves holes.
+  var holey = [void 0,'a',,'c'].concat(['d',,'f',[0,,2],void 0])
+  assertEquals(9, holey.length);  // hole in embedded array is ignored
+  for (var i = 0; i < holey.length; i++) {
+    if (i == 2 || i == 5) {
+      assertFalse(i in holey);
+    } else {
+      assertTrue(i in holey);
+    }
+  }
+
+  // Polluted prototype from prior tests.
+  delete Array.prototype[123];
+
+  // Check that concat reads getters in the correct order.
+  var arr1 = [,2];
+  var arr2 = [1,3];
+  var r1 = [].concat(arr1, arr2);  // [,2,1,3]
+  assertEquals([,2,1,3], r1);
+
+  // Make first array change length of second array.
+  Object.defineProperty(arr1, 0, {get: function() {
+        arr2.push("X");
+        return undefined;
+      }, configurable: true})
+  var r2 = [].concat(arr1, arr2);  // [undefined,2,1,3,"X"]
+  assertEquals([undefined,2,1,3,"X"], r2);
+
+  // Make first array change length of second array massively.
+  arr2.length = 2;
+  Object.defineProperty(arr1, 0, {get: function() {
+        arr2[500000] = "X";
+        return undefined;
+      }, configurable: true})
+  var r3 = [].concat(arr1, arr2);  // [undefined,2,1,3,"X"]
+  var expected = [undefined,2,1,3];
+  expected[500000 + 2] = "X";
+
+  assertEquals(expected, r3);
+
+  var arr3 = [];
+  var trace = [];
+  var expectedTrace = []
+  function mkGetter(i) { return function() { trace.push(i); }; }
+  arr3.length = 10000;
+  for (var i = 0; i < 100; i++) {
+    Object.defineProperty(arr3, i * i, {get: mkGetter(i)});
+    expectedTrace[i] = i;
+    expectedTrace[100 + i] = i;
+  }
+  var r4 = [0].concat(arr3, arr3);
+  assertEquals(1 + arr3.length * 2, r4.length);
+  assertEquals(expectedTrace, trace);
+})();