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Fix Array.prototype.copyWithin polyfill #2902

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Fix Array.prototype.copyWithin polyfill #2902

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a0e0782
Fix Array.prototype.copyWithin polyfill
teppeis Apr 21, 2018
e3a9f62
remove .name and .length polyfill, merge js/util/tointeger.js
teppeis Dec 28, 2018
ee70045
Fix tests for Array.prototype.copyWithin polyfill
teppeis Jan 16, 2019
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49 changes: 33 additions & 16 deletions src/com/google/javascript/jscomp/js/es6/array/copywithin.js
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,9 @@
'require util/polyfill';

$jscomp.polyfill('Array.prototype.copyWithin', function(orig) {
// requires strict mode to throw for invalid `this` or params
'use strict';

if (orig) return orig;

/**
Expand All @@ -31,32 +34,46 @@ $jscomp.polyfill('Array.prototype.copyWithin', function(orig) {
*/
var polyfill = function(target, start, opt_end) {
var len = this.length;
target = Number(target);
start = Number(start);
opt_end = Number(opt_end != null ? opt_end : len);
if (target < start) {
opt_end = Math.min(opt_end, len);
while (start < opt_end) {
if (start in this) {
this[target++] = this[start++];
target = toInteger(target);
start = toInteger(start);
var end = opt_end === undefined ? len : toInteger(opt_end);
var to = target < 0 ? Math.max(len + target, 0) : Math.min(target, len);
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var from = start < 0 ? Math.max(len + start, 0) : Math.min(start, len);
var final = end < 0 ? Math.max(len + end, 0) : Math.min(end, len);
if (to < from) {
while (from < final) {
if (from in this) {
this[to++] = this[from++];
} else {
delete this[target++];
start++;
delete this[to++];
from++;
}
}
} else {
opt_end = Math.min(opt_end, len + start - target);
target += opt_end - start;
while (opt_end > start) {
if (--opt_end in this) {
this[--target] = this[opt_end];
final = Math.min(final, len + from - to);
to += final - from;
while (final > from) {
if (--final in this) {
this[--to] = this[final];
} else {
delete this[target];
delete this[--to];
}
}
}
return this;
};

/**
* @param {number} arg
* @return {number}
*/
function toInteger(arg) {
var n = Number(arg);
if (n === Infinity || n === -Infinity) {
return n;
}
return n | 0;
};

return polyfill;
}, 'es6', 'es3');
50 changes: 50 additions & 0 deletions test/com/google/javascript/jscomp/runtime_tests/polyfill_tests/array_copywithin_test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -64,5 +64,55 @@ testSuite({
arr = {length: 3, 1: 4, 3: 'unused'};
assertEquals(arr, Array.prototype.copyWithin.call(noCheck(arr), 0, 1));
assertObjectEquals({length: 3, 0: 4, 3: 'unused'}, arr);

arr = {length: 3, 1: 4, 3: 'unused'};
assertEquals(arr, Array.prototype.copyWithin.call(noCheck(arr), 1, 0));
assertObjectEquals({length: 3, 2: 4, 3: 'unused'}, arr);
},

testCopyWithin_coercingArgs() {
assertObjectEquals([1, 2, 3, 3], [0, 1, 2, 3].copyWithin(NaN, 1));
assertObjectEquals([1, 2, 3, 3], [0, 1, 2, 3].copyWithin(0.5, 1));
assertObjectEquals([0, 0, 1, 2], [0, 1, 2, 3].copyWithin(1.5, 0));

assertObjectEquals([0, 0, 1, 2], [0, 1, 2, 3].copyWithin(1, NaN));
assertObjectEquals([0, 0, 1, 2], [0, 1, 2, 3].copyWithin(1, 0.5));
assertObjectEquals([1, 2, 3, 3], [0, 1, 2, 3].copyWithin(0, 1.5));

assertObjectEquals([0, 1, 2, 3], [0, 1, 2, 3].copyWithin(1, 0, NaN));
assertObjectEquals([0, 0, 2, 3], [0, 1, 2, 3].copyWithin(1, 0, 1.5));
assertObjectEquals([0, 0, 1, 3], [0, 1, 2, 3].copyWithin(1, 0, -2.5));
assertObjectEquals([0, 0, 1, 2], [0, 1, 2, 3].copyWithin(1, 0, undefined));
},

testCopyWithin_negativeArgs() {
assertObjectEquals([1, 2, 3, 1, 2], [1, 2, 3, 4, 5].copyWithin(-2, 0));
assertObjectEquals([1, 3, 4, 5, 5], [1, 2, 3, 4, 5].copyWithin(1, -3));
assertObjectEquals([1, 3, 4, 4, 5], [1, 2, 3, 4, 5].copyWithin(1, 2, -1));
},

testCopyWithin_throwsIfNullish() {
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This test no longer passes. Please remove it.

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Really? It should be pass and I believe it passes.

this is null and this.length is referred on the top of the polyfill function, so it should throw an error.
https://github.com/google/closure-compiler/pull/2902/files#diff-a5e0f0788d56ad46f3db1223fd3c8b5cR36

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@tjgq tjgq Jan 16, 2019 •
edited
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I didn't look close enough: it fails because the start and target arguments are not optional (unfortunately, I don't think there's a way to run the polyfill tests externally, so there's no way for you to reproduce it). The best you can do is something like this:

Array.prototype.copyWithin.call(null, some_other_array, 0);

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@tjgq understood. It is not a runtime test, but a type check failed. I added the second and the third argument.

assertThrows(function() {
Array.prototype.copyWithin.call(null, 0, 0);
});
assertThrows(function() {
Array.prototype.copyWithin.call(undefined, 0, 0);
});
},

testCopyWithin_throwIfFailToDeleteProperty() {
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Same as above.

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@tjgq Probably type check in 2nd arg of Object.defineProperty() failed, so I fixed it.

var obj = {
length: 5
};

Object.defineProperty(obj, '4', {
value: 'a',
configurable: false,
writable: true
});

assertThrows(function() {
Array.prototype.copyWithin.call(noCheck(obj), 4, 0);
});
},
});