mirror of https://github.com/tc39/test262.git
78 lines
2.0 KiB
JavaScript
78 lines
2.0 KiB
JavaScript
// Copyright (C) 2019 André Bargull. 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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esid: sec-runtime-semantics-forin-div-ofbodyevaluation-lhs-stmt-iterator-lhskind-labelset
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description: >
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Ensure the number of ticks and Promise constructor lookups is correct with custom async iterator.
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info: |
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13.7.5.13 Runtime Semantics: ForIn/OfBodyEvaluation ( lhs, stmt, iteratorRecord, iterationKind,
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lhsKind, labelSet [ , iteratorKind ] )
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6.2.3.1 Await
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includes: [compareArray.js]
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flags: [async]
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features: [async-iteration]
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---*/
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// The expected event log.
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var expected = [
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// Before entering loop.
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"pre",
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// Await promise resolved.
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"tick 1",
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// In loop body.
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"loop",
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// Await promise resolved
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"tick 2",
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// After exiting loop.
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"post",
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];
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// The actual event log.
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var actual = [];
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// Custom async iterator directly using a synchronous iterator.
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function toAsyncIterator(iterable) {
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return {
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[Symbol.asyncIterator]() {
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return iterable[Symbol.iterator]();
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}
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};
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}
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// Test function using for-await with a single, already resolved Promise.
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async function f() {
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var p = Promise.resolve(0);
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actual.push("pre");
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for await (var x of toAsyncIterator([p])) {
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actual.push("loop");
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}
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actual.push("post");
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}
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// Count the number of ticks needed to complete the loop and compare the actual log.
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Promise.resolve(0)
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.then(() => actual.push("tick 1"))
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.then(() => actual.push("tick 2"))
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.then(() => {
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assert.compareArray(actual, expected, "Ticks and constructor lookups");
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}).then($DONE, $DONE);
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// Redefine `Promise.constructor` in order to intercept "constructor" lookups from PromiseResolve.
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// (Perform last so that the lookups from SpeciesConstructor in `then` aren't logged.)
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Object.defineProperty(Promise.prototype, "constructor", {
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get() {
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actual.push("constructor");
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return Promise;
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},
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configurable: true,
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});
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// Start the asynchronous function.
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f();
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