Fix stuck tasks when proxied task using a proxy progress task

completes before the proxy task has been started by task manager

Fixes #21589, fixes #19761

(cherry picked from commit b28227f)

Author: nyalldawson

src/core/qgsproxyprogresstask.cpp

@@ -25,14 +25,20 @@ QgsProxyProgressTask::QgsProxyProgressTask( const QString &description )
 
 void QgsProxyProgressTask::finalize( bool result )
 {
+  QMutexLocker lock( &mNotFinishedMutex );
+  mAlreadyFinished = true;
+
   mResult = result;
   mNotFinishedWaitCondition.wakeAll();
 }
 
 bool QgsProxyProgressTask::run()
 {
   mNotFinishedMutex.lock();
-  mNotFinishedWaitCondition.wait( &mNotFinishedMutex );
+  if ( !mAlreadyFinished )
+  {
+    mNotFinishedWaitCondition.wait( &mNotFinishedMutex );
+  }
   mNotFinishedMutex.unlock();
 
   return mResult;

src/core/qgsproxyprogresstask.h

@@ -64,6 +64,7 @@ class CORE_EXPORT QgsProxyProgressTask : public QgsTask
 
     QWaitCondition mNotFinishedWaitCondition;
     QMutex mNotFinishedMutex;
+    bool mAlreadyFinished = false;
     bool mResult = true;
 
 };

tests/src/core/testqgstaskmanager.cpp

@@ -19,6 +19,7 @@
 #include "qgsproject.h"
 #include "qgsvectorlayer.h"
 #include "qgsapplication.h"
+#include "qgsproxyprogresstask.h"
 #include <QObject>
 #include "qgstest.h"
 
@@ -270,6 +271,9 @@ class TestQgsTaskManager : public QObject
     void managerWithSubTasks2();
     void managerWithSubTasks3();
     void cancelBeforeStart();
+    void proxyTask();
+    void proxyTask2();
+    void scopedProxyTask();
 };
 
 void TestQgsTaskManager::initTestCase()
@@ -1374,5 +1378,75 @@ void TestQgsTaskManager::cancelBeforeStart()
   flushEvents();
 }
 
+void TestQgsTaskManager::proxyTask()
+{
+  if ( QgsTest::isTravis() )
+    QSKIP( "This test is disabled on Travis CI environment" );
+
+  QgsProxyProgressTask *proxyTask = new QgsProxyProgressTask( QString() );
+
+  // finalize before task gets a chance to start
+  QgsTaskManager manager;
+  proxyTask->finalize( false );
+  QPointer< QgsTask > p( proxyTask );
+
+  manager.addTask( proxyTask );
+
+  // should all be ok, no deadlock...
+  while ( p )
+  {
+    QCoreApplication::processEvents();
+  }
+  flushEvents();
+}
+
+void TestQgsTaskManager::proxyTask2()
+{
+  if ( QgsTest::isTravis() )
+    QSKIP( "This test is disabled on Travis CI environment" );
+
+  QgsProxyProgressTask *proxyTask = new QgsProxyProgressTask( QString() );
+
+  // finalize before task gets a chance to start
+  QgsTaskManager manager;
+  QPointer< QgsTask > p( proxyTask );
+  manager.addTask( proxyTask );
+
+  // should all be ok, no deadlock...
+  while ( proxyTask->status() != QgsTask::Running )
+  {
+    QCoreApplication::processEvents();
+  }
+  proxyTask->finalize( false );
+  while ( p )
+  {
+    QCoreApplication::processEvents();
+  }
+
+  flushEvents();
+}
+
+void TestQgsTaskManager::scopedProxyTask()
+{
+  if ( QgsTest::isTravis() )
+    QSKIP( "This test is disabled on Travis CI environment" );
+
+  {
+    // task finishes before it can start
+    QgsScopedProxyProgressTask task{ QString() };
+  }
+
+  // should all be ok, no deadlock...
+  while ( QgsApplication::taskManager()->countActiveTasks() == 0 )
+  {
+    QCoreApplication::processEvents();
+  }
+  while ( QgsApplication::taskManager()->countActiveTasks() > 0 )
+  {
+    QCoreApplication::processEvents();
+  }
+  flushEvents();
+}
+
 QGSTEST_MAIN( TestQgsTaskManager )
 #include "testqgstaskmanager.moc"