tor-browser

The Tor Browser
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ticks-with-sync-iter-resolved-promise-and-constructor-lookup.js (2394B)

      1 // |reftest| async
      2 // Copyright (C) 2019 André Bargull. All rights reserved.
      3 // This code is governed by the BSD license found in the LICENSE file.
      4 
      5 /*---
      6 esid: sec-runtime-semantics-forin-div-ofbodyevaluation-lhs-stmt-iterator-lhskind-labelset
      7 description: >
      8  Ensure the number of ticks and Promise constructor lookups is correct with a Async-from-Sync iterator.
      9 info: |
     10  13.7.5.13 Runtime Semantics: ForIn/OfBodyEvaluation ( lhs, stmt, iteratorRecord, iterationKind,
     11                                                        lhsKind, labelSet [ , iteratorKind ] )
     12  25.1.4.2.1 %AsyncFromSyncIteratorPrototype%.next
     13  25.1.4.4 AsyncFromSyncIteratorContinuation
     14  25.6.4.5.1 PromiseResolve
     15  6.2.3.1 Await
     16 
     17 includes: [compareArray.js]
     18 flags: [async]
     19 features: [async-iteration]
     20 ---*/
     21 
     22 // The expected event log.
     23 var expected = [
     24  // Before entering loop.
     25  "pre",
     26 
     27  // %AsyncFromSyncIteratorPrototype%.next
     28  // -> AsyncFromSyncIteratorContinuation
     29  //   -> PromiseResolve
     30  "constructor",
     31 
     32  // Await
     33  // -> PromiseResolve
     34  "constructor",
     35 
     36  // Async-from-Sync Iterator promise resolved.
     37  "tick 1",
     38 
     39  // Await promise resolved.
     40  "tick 2",
     41 
     42  // In loop body.
     43  "loop",
     44 
     45  // Await
     46  // -> PromiseResolve
     47  "constructor",
     48 
     49  // Async-from-Sync Iterator promise resolved.
     50  "tick 3",
     51 
     52  // Await promise resolved
     53  "tick 4",
     54 
     55  // After exiting loop.
     56  "post",
     57 ];
     58 
     59 // The actual event log.
     60 var actual = [];
     61 
     62 // Test function using for-await with a single, already resolved Promise.
     63 async function f() {
     64  var p = Promise.resolve(0);
     65  actual.push("pre");
     66  for await (var x of [p]) {
     67    actual.push("loop");
     68  }
     69  actual.push("post");
     70 }
     71 
     72 // Count the number of ticks needed to complete the loop and compare the actual log.
     73 Promise.resolve(0)
     74  .then(() => actual.push("tick 1"))
     75  .then(() => actual.push("tick 2"))
     76  .then(() => actual.push("tick 3"))
     77  .then(() => actual.push("tick 4"))
     78  .then(() => {
     79    assert.compareArray(actual, expected, "Ticks and constructor lookups");
     80 }).then($DONE, $DONE);
     81 
     82 // Redefine `Promise.constructor` in order to intercept "constructor" lookups from PromiseResolve.
     83 // (Perform last so that the lookups from SpeciesConstructor in `then` aren't logged.)
     84 Object.defineProperty(Promise.prototype, "constructor", {
     85  get() {
     86    actual.push("constructor");
     87    return Promise;
     88  },
     89  configurable: true,
     90 });
     91 
     92 // Start the asynchronous function.
     93 f();