From e3fae6eeb4ca3b4ead683050e470504a35c56ccb Mon Sep 17 00:00:00 2001
From: Mike Pennisi <mike@mikepennisi.com>
Date: Wed, 10 Feb 2016 13:56:55 -0500
Subject: [PATCH] Promise: Add test for constructor access count
Assert that the `constructor` property of the "this" value of
`Promise.prototype.then` is accessed exactly once. This guards against
implementations where repeated access is used instead of reference
passing (possibly motivated by convenience).
Repeated access of this kind was demonstrated by V8's implementation of
the specification:
https://bugs.chromium.org/p/v8/issues/detail?id=4539
---
.../prototype/then/ctor-access-count.js | 48 +++++++++++++++++++
1 file changed, 48 insertions(+)
create mode 100644 test/built-ins/Promise/prototype/then/ctor-access-count.js
diff --git a/test/built-ins/Promise/prototype/then/ctor-access-count.js b/test/built-ins/Promise/prototype/then/ctor-access-count.js
new file mode 100644
index 0000000000..e01e593cd6
--- /dev/null
+++ b/test/built-ins/Promise/prototype/then/ctor-access-count.js
@@ -0,0 +1,48 @@
+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+es6id: 25.4.5.3
+description: The instance's `constructor` property is accessed exactly once
+info: >
+ 1. Let promise be the this value.
+ 2. If IsPromise(promise) is false, throw a TypeError exception.
+ 3. Let C be SpeciesConstructor(promise, %Promise%).
+ 4. ReturnIfAbrupt(C).
+ 5. Let resultCapability be NewPromiseCapability(C).
+ 6. ReturnIfAbrupt(resultCapability).
+ 7. Return PerformPromiseThen(promise, onFulfilled, onRejected,
+ resultCapability).
+
+ 7.3.20 SpeciesConstructor ( O, defaultConstructor )
+
+ 1. Assert: Type(O) is Object.
+ 2. Let C be Get(O, "constructor").
+ 3. ReturnIfAbrupt(C).
+ 4. If C is undefined, return defaultConstructor.
+ 5. If Type(C) is not Object, throw a TypeError exception.
+ 6. Let S be Get(C, @@species).
+ 7. ReturnIfAbrupt(S).
+ 8. If S is either undefined or null, return defaultConstructor.
+ 9. If IsConstructor(S) is true, return S.
+ 10. Throw a TypeError exception.
+---*/
+
+var callCount = 0;
+var prms = new Promise(function(resolve) { resolve(); });
+Object.defineProperty(prms, 'constructor', {
+ get: function() {
+ callCount += 1;
+ return Promise;
+ }
+});
+
+prms.then(function() {
+ if (callCount !== 1) {
+ $DONE('Expected constructor access count: 1. Actual: ' + callCount);
+ return;
+ }
+
+ $DONE();
+ }, function() {
+ $DONE('The promise should not be rejected.');
+ });
--
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