Cocoa WorkQueue::dispatchWithQOS() and dispatch() work item lifetime …

…semantics do not match

https://bugs.webkit.org/show_bug.cgi?id=260852
rdar://114618174

Reviewed by Jean-Yves Avenard and Chris Dumez.

dispatch() users expect the work function to be destructed in the
queue

Add the same semantic to dispatchWithQOS() to avoid confusion in the
code and to have uniform interface.

* Source/WTF/wtf/cocoa/WorkQueueCocoa.cpp:
(WTF::WorkQueueBase::dispatchWithQOS):
* Tools/TestWebKitAPI/Tests/WTF/WorkQueue.cpp:
(TestWebKitAPI::TEST):

Canonical link: https://commits.webkit.org/267776@main

Source/WTF/wtf/cocoa/WorkQueueCocoa.cpp

@@ -56,8 +56,9 @@ void WorkQueueBase::dispatch(Function<void()>&& function)
 
 void WorkQueueBase::dispatchWithQOS(Function<void()>&& function, QOS qos)
 {
-    dispatch_block_t blockWithQOS = dispatch_block_create_with_qos_class(DISPATCH_BLOCK_ENFORCE_QOS_CLASS, Thread::dispatchQOSClass(qos), 0, makeBlockPtr([function = WTFMove(function)] {
+    dispatch_block_t blockWithQOS = dispatch_block_create_with_qos_class(DISPATCH_BLOCK_ENFORCE_QOS_CLASS, Thread::dispatchQOSClass(qos), 0, makeBlockPtr([function = WTFMove(function)] () mutable {
         function();
+        function = { };
     }).get());
     dispatch_async(m_dispatchQueue.get(), blockWithQOS);
 #if !__has_feature(objc_arc)

Tools/TestWebKitAPI/Tests/WTF/WorkQueue.cpp

@@ -306,9 +306,14 @@ TEST(WTF_WorkQueue, DestroyDispatchedOnDispatchQueue)
         for (size_t j = 0; j < queueCount; ++j)
             queue[j]->dispatch([instance = std::make_unique<DestructionWorkQueueTester>(counter, *queue[j])] { }); // NOLINT
     }
+    // dispatchQOS() behaves the same as dispatch().
+    for (size_t i = 0; i < iterationCount; ++i) {
+        for (size_t j = 0; j < queueCount; ++j)
+            queue[j]->dispatchWithQOS([instance = std::make_unique<DestructionWorkQueueTester>(counter, *queue[j])] { }, Thread::QOS::UserInteractive); // NOLINT
+    }
     for (size_t j = 0; j < queueCount; ++j)
         queue[j]->dispatchSync([] { });
-    EXPECT_EQ(queueCount * iterationCount, counter);
+    EXPECT_EQ(2u * queueCount * iterationCount, counter);
 }
 
 namespace {