From bf3fc5c95cb4e6acedf242c00b7a1c3b455062bb Mon Sep 17 00:00:00 2001
From: Sona Kurazyan <sona.kurazyan@qt.io>
Date: Mon, 20 Jun 2022 15:46:00 +0200
Subject: [PATCH] QPromise: run continuation(s) on destruction

If the QFuture is canceled because the associated QPromise has been
destroyed, we still need to run its continuations (i.e. onCanceled
handler, if it's attached), so replaced the cleanContinuation() call
inside ~QPromise() with runContinuation(), which will also take care of
cleaning the continuation.

[ChangeLog][QtCore][Important Behavior Changes] QFuture now runs its
continuations when its associated QPromise has been destroyed.
Previously, if a QFuture was canceled because the associated QPromise
has been destroyed, its continuations were skipped.

Fixes: QTBUG-103992
Pick-to: 6.4 6.3 6.2
Change-Id: Ie05bc760c96c349aade8adb8d2fe5263aff8efac
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
---
 src/corelib/thread/qpromise.h                 |  2 +-
 .../corelib/thread/qpromise/tst_qpromise.cpp  | 20 +++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/corelib/thread/qpromise.h b/src/corelib/thread/qpromise.h
index a3ad04648bd..d0f6e6ae66e 100644
--- a/src/corelib/thread/qpromise.h
+++ b/src/corelib/thread/qpromise.h
@@ -39,7 +39,7 @@ public:
         // potential waits
         if (d.d && !(d.loadState() & QFutureInterfaceBase::State::Finished)) {
             d.cancelAndFinish(); // cancel and finalize the state
-            d.cleanContinuation();
+            d.runContinuation();
         }
     }
 
diff --git a/tests/auto/corelib/thread/qpromise/tst_qpromise.cpp b/tests/auto/corelib/thread/qpromise/tst_qpromise.cpp
index 5de8ce13ab2..12206aa9fc9 100644
--- a/tests/auto/corelib/thread/qpromise/tst_qpromise.cpp
+++ b/tests/auto/corelib/thread/qpromise/tst_qpromise.cpp
@@ -40,6 +40,7 @@ private slots:
 #endif
     void cancelWhenReassigned();
     void cancelWhenDestroyedWithoutStarting();
+    void cancelWhenDestroyedRunsContinuations();
     void finishWhenSwapped();
     void cancelWhenMoved();
     void waitUntilResumed();
@@ -494,6 +495,25 @@ void tst_QPromise::cancelWhenDestroyedWithoutStarting()
     QVERIFY(future.isFinished());
 }
 
+void tst_QPromise::cancelWhenDestroyedRunsContinuations()
+{
+    QFuture<void> future;
+    bool onCanceledCalled = false;
+    bool thenCalled = false;
+    {
+        QPromise<void> promise;
+        future = promise.future();
+        future.then([&] {
+            thenCalled = true;
+        }).onCanceled([&] {
+            onCanceledCalled = true;
+        });
+    }
+    QVERIFY(future.isFinished());
+    QVERIFY(!thenCalled);
+    QVERIFY(onCanceledCalled);
+}
+
 void tst_QPromise::finishWhenSwapped()
 {
 #if !QT_CONFIG(cxx11_future)