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A subtle aspect of the for-of iteration protocol concerns abrupt completions that do *not* trigger iterator closing. Although this detail is implicit in the current structure of the specification text, some hosts may violate the protocol by closing the iterator because later steps *do* specify that behavior. The V8 engine is one such host--as of this writing, it incorrectly closes the iterator when accessing the `value` property of the iterator result produces an abrupt completion. Add tests verifying that the iterator protocol is not violated in this way for abrupt completions during the semantics of for-of evaluation.
46 lines
1.1 KiB
JavaScript
46 lines
1.1 KiB
JavaScript
// Copyright (C) 2015 the V8 project authors. All rights reserved.
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// This code is governed by the BSD license found in the LICENSE file.
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/*---
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es6id: 13.6.4.13 S5.g
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description: >
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If `nextValue` is an abrupt completion as per IteratorValue (ES6 7.4.4),
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return the completion.
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info: |
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[...]
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5. Repeat
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a. Let nextResult be ? IteratorStep(iterator).
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b. If nextResult is false, return NormalCompletion(V).
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c. Let nextValue be ? IteratorValue(nextResult).
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features: [Symbol.iterator]
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---*/
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var iterable = {};
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var iterationCount = 0;
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var returnCount = 0;
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iterable[Symbol.iterator] = function() {
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return {
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next: function() {
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return {
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done: false,
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get value() {
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throw new Test262Error();
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}
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};
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},
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return: function() {
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returnCount += 1;
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return {};
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}
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};
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};
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assert.throws(Test262Error, function() {
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for (var x of iterable) {
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iterationCount += 1;
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}
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});
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assert.sameValue(iterationCount, 0, 'The loop body is not evaluated');
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assert.sameValue(returnCount, 0, 'Iterator is not closed.');
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