QTestLib: flush DeferredDelete events between every test

This makes qtestlib behave more like real Qt applications with an
event loop, where exiting the application does indeed flush deleteLaters.
And since every test method is supposed to be independent from other
test methods, we should even cleanup between tests.

For "app less" tests, no flushing happens.

Real life use cases:

* A unittest for some code (e.g. KIO job) which uses a socket, runs an
event loop until the socket communication is done, and ends. However
slotDisconnected() does, as recommended, socket->deleteLater(). So the
test finishes before the socket has a chance to actually get deleted,
and memory leak tools flag a memory leak, which doesn't actually happen
outside the unittest.

* Deleting a QWebEngineView with deleteLater is even worse than a memleak,
it leads to an assert (from a global object destructor) in QtWebEngine
if the view deletion hasn't actually been processed.

Change-Id: I18fc822fd26988a0fa4e75313c1947fcaa7d9e56
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/testlib/qtestcase.cpp

@@ -901,6 +901,10 @@ void TestMethods::invokeTestOnData(int index) const
             if (m_cleanupMethod.isValid())
                 m_cleanupMethod.invoke(QTest::currentTestObject, Qt::DirectConnection);
 
+            // Process any deleteLater(), like event-loop based apps would do. Fixes memleak reports.
+            if (QCoreApplication::instance())
+                QCoreApplication::sendPostedEvents(nullptr, QEvent::DeferredDelete);
+
             // If the test isn't a benchmark, finalize the result after cleanup() has finished.
             if (!isBenchmark)
                 QTestResult::finishedCurrentTestDataCleanup();

tests/auto/testlib/selftests/deleteLater/deleteLater.pro

@@ -0,0 +1,7 @@
+SOURCES += tst_deleteLater.cpp
+QT = core testlib
+
+CONFIG -= app_bundle
+CONFIG -= debug_and_release_target
+
+TARGET = tst_deleteLater

tests/auto/testlib/selftests/deleteLater/tst_deleteLater.cpp

@@ -0,0 +1,87 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 Klaralvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author David Faure <david.faure@kdab.com>
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+
+#include <QtCore/QCoreApplication>
+#include <QtTest/QtTest>
+
+class tst_DeleteLater: public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void qtestLibShouldFlushDeleteLaterBetweenTests_setup();
+    void qtestLibShouldFlushDeleteLaterBetweenTests_check();
+    void qtestLibShouldFlushDeleteLaterOnExit();
+};
+
+class ToBeDeleted : public QObject
+{
+public:
+    ToBeDeleted(bool *staticBool) : staticBool(staticBool) {}
+    ~ToBeDeleted() { *staticBool = true; }
+private:
+    bool *staticBool;
+};
+
+static bool deletedBetweenTests = false;
+
+void tst_DeleteLater::qtestLibShouldFlushDeleteLaterBetweenTests_setup()
+{
+    ToBeDeleted *obj = new ToBeDeleted(&deletedBetweenTests);
+    obj->deleteLater();
+}
+
+void tst_DeleteLater::qtestLibShouldFlushDeleteLaterBetweenTests_check()
+{
+    QVERIFY(deletedBetweenTests);
+}
+
+static bool deletedOnExit = false;
+
+void tst_DeleteLater::qtestLibShouldFlushDeleteLaterOnExit()
+{
+    ToBeDeleted *obj = new ToBeDeleted(&deletedOnExit);
+    obj->deleteLater();
+}
+
+// This global object will check whether the deleteLater was processed
+class DeleteChecker
+{
+public:
+    ~DeleteChecker() {
+        if (!deletedOnExit) {
+            qFatal("QTestLib failed to flush deleteLater on exit");
+        }
+    }
+};
+static DeleteChecker s_deleteChecker;
+
+QTEST_MAIN(tst_DeleteLater)
+
+#include "tst_deleteLater.moc"

tests/auto/testlib/selftests/deleteLater_noApp/deleteLater_noApp.pro

@@ -0,0 +1,7 @@
+SOURCES += tst_deleteLater_noApp.cpp
+QT = core testlib
+
+CONFIG -= app_bundle
+CONFIG -= debug_and_release_target
+
+TARGET = tst_deleteLater_noApp

tests/auto/testlib/selftests/deleteLater_noApp/tst_deleteLater_noApp.cpp

@@ -0,0 +1,88 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 Klaralvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author David Faure <david.faure@kdab.com>
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+
+#include <QtCore/QCoreApplication>
+#include <QtTest/QtTest>
+
+class tst_DeleteLater_noApp: public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void qtestLibShouldNotFlushDeleteLaterBetweenTests_setup();
+    void qtestLibShouldNotFlushDeleteLaterBetweenTests_check();
+    void qtestLibShouldNotFlushDeleteLaterOnExit();
+};
+
+class ToBeDeleted : public QObject
+{
+public:
+    ToBeDeleted(bool *staticBool) : staticBool(staticBool) {}
+    ~ToBeDeleted() { *staticBool = true; }
+private:
+    bool *staticBool;
+};
+
+static bool deletedBetweenTests = false;
+
+void tst_DeleteLater_noApp::qtestLibShouldNotFlushDeleteLaterBetweenTests_setup()
+{
+    ToBeDeleted *obj = new ToBeDeleted(&deletedBetweenTests);
+    obj->deleteLater();
+}
+
+void tst_DeleteLater_noApp::qtestLibShouldNotFlushDeleteLaterBetweenTests_check()
+{
+    // There's no qApp, we can't flush the events
+    QVERIFY(!deletedBetweenTests);
+}
+
+static bool deletedOnExit = false;
+
+void tst_DeleteLater_noApp::qtestLibShouldNotFlushDeleteLaterOnExit()
+{
+    ToBeDeleted *obj = new ToBeDeleted(&deletedOnExit);
+    obj->deleteLater();
+}
+
+// This global object will check whether the deleteLater was processed
+class DeleteChecker
+{
+public:
+    ~DeleteChecker() {
+        if (deletedOnExit) {
+            qFatal("QTestLib somehow flushed deleteLater on exit, without a qApp?");
+        }
+    }
+};
+static DeleteChecker s_deleteChecker;
+
+QTEST_APPLESS_MAIN(tst_DeleteLater_noApp)
+
+#include "tst_deleteLater_noApp.moc"

tests/auto/testlib/selftests/selftests.pri

@@ -15,6 +15,8 @@ SUBPROGRAMS = \
      crashes \
      datatable \
      datetime \
+     deleteLater \
+     deleteLater_noApp \
      differentexec \
      exceptionthrow \
      expectfail \