Implement Array.from()

test/mjsunit/harmony/array-from.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

[arv (Not doing code reviews), 2014/07/02 18:26:44]

Use more specific flag(s).

+
+assertEquals(1, Array.from.length);
+
+assertArrayEquals(Array.from(NaN), []);
+assertArrayEquals(Array.from(Infinity), []);
+assertArrayEquals(Array.from(10000000), []);
+assertArrayEquals(Array.from('test'), ['t', 'e', 's', 't']);
+assertArrayEquals(Array.from({length: 1, '0': { 'foo': 'bar' }}), [{'foo': 'bar'}]);

[arv (Not doing code reviews), 2014/07/02 18:26:44]

Can you add test with length = -1

I wish we could also test length = Infinity, but even at 2^53-1 it would take
too long.

+assertArrayEquals(Array.from(['foo', 'bar', 'baz']), ['foo', 'bar', 'baz']);
+assertArrayEquals(Array.from((new Set).add('foo').add('bar').add('baz')), ['foo', 'bar', 'baz']);
+assertArrayEquals(Array.from((new Map).set(0, 'foo').set(1, 'bar').set(2, 'baz')), [[0, 'foo'], [1, 'bar'], [2, 'baz']]);
+assertArrayEquals(Array.from(generator()), ['a', 'b', 'c']);
+assertArrayEquals(Array.from('test', function(x) {
+  return this.filter(x);
+}, {
+  filter: function(x) { return x.toUpperCase(); }
+}), ['T', 'E', 'S', 'T']);
+assertArrayEquals(Array.from('test', function(x) {
+  return x.toUpperCase();
+}), ['T', 'E', 'S', 'T']);
+
+// Mozilla:
+// Array.from on a string handles surrogate pairs correctly.
+var gclef = "\uD834\uDD1E"; // U+1D11E MUSICAL SYMBOL G CLEF
+assertArrayEquals(Array.from(gclef), [gclef]);
+assertArrayEquals(Array.from(gclef + " G"), [gclef, " ", "G"]);
+
+function* generator() {
+  var a = ['a', 'b', 'c'];

[arv (Not doing code reviews), 2014/07/02 18:26:43]

function* generator() {
  yield 'a';
  yield 'b';
  yield 'c';
}

+  var n = 0;
+  while (n < a.length) {
+    yield a[n++];
+  }
+}
+
+assertThrows('Array.from(null)', TypeError);
+assertThrows('Array.from(undefined)', TypeError);
+
+var nullIterator = {};
+nullIterator[Symbol.iterator] = null;
+assertThrows('Array.from(nullIterator)', TypeError);
+
+var nonObjIterator = {};
+nonObjIterator[Symbol.iterator] = function() { return "nonObject"; };
+assertThrows('Array.from(nonObjIterator)', TypeError);
+
+assertThrows('Array.from([], null)', TypeError);

[arv (Not doing code reviews), 2014/07/02 18:26:43]

This needs more tests. Especially things like calling Array.from.call(func, [0,
1, 2]) where the returned instance should not be an array.

Also, need to test that we put length (use a setter)

Also, things like checking the order of things as well as the number of times we
read certain properties are important.