Introduce AutoDeleteReplyOnFinishAttribute for QNetworkRequest

[ChangeLog][QtNetwork][QNetworkRequest] Added the
AutoDeleteReplyOnFinishAttribute attribute to QNetworkRequest, which
makes QNetworkAccessManager delete the QNetworkReply after it has
emitted the "finished" signal.

Change-Id: I03d4ac0830137882e51dd28795a8ec817762a300
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

src/network/access/qnetworkaccessmanager.cpp

@@ -1677,8 +1677,11 @@ void QNetworkAccessManagerPrivate::_q_replyFinished()
     Q_Q(QNetworkAccessManager);
 
     QNetworkReply *reply = qobject_cast<QNetworkReply *>(q->sender());
-    if (reply)
+    if (reply) {
         emit q->finished(reply);
+        if (reply->request().attribute(QNetworkRequest::AutoDeleteReplyOnFinishAttribute, false).toBool())
+            QMetaObject::invokeMethod(reply, [reply] { reply->deleteLater(); }, Qt::QueuedConnection);
+    }
 
 #ifndef QT_NO_BEARERMANAGEMENT
     // If there are no active requests, release our reference to the network session.

src/network/access/qnetworkrequest.cpp

@@ -331,6 +331,12 @@ QT_BEGIN_NAMESPACE
 
     \omitvalue ResourceTypeAttribute
 
+    \value AutoDeleteReplyOnFinishAttribute
+        Requests only, type: QMetaType::Bool (default: false)
+        If set, this attribute will make QNetworkAccessManager delete
+        the QNetworkReply after having emitted "finished".
+        (This value was introduced in 5.14.)
+
     \value User
         Special type. Additional information can be passed in
         QVariants with types ranging from User to UserMax. The default

src/network/access/qnetworkrequest.h

@@ -98,6 +98,7 @@ public:
         RedirectPolicyAttribute,
         Http2DirectAttribute,
         ResourceTypeAttribute, // internal
+        AutoDeleteReplyOnFinishAttribute,
 
         User = 1000,
         UserMax = 32767

tests/auto/network/access/qnetworkreply/tst_qnetworkreply.cpp

@@ -503,6 +503,9 @@ private Q_SLOTS:
     void putWithServerClosingConnectionImmediately();
 #endif
 
+    void autoDeleteRepliesAttribute_data();
+    void autoDeleteRepliesAttribute();
+
     // NOTE: This test must be last!
     void parentingRepliesToTheApp();
 private:
@@ -9167,6 +9170,77 @@ void tst_QNetworkReply::putWithServerClosingConnectionImmediately()
 
 #endif
 
+void tst_QNetworkReply::autoDeleteRepliesAttribute_data()
+{
+    QTest::addColumn<QUrl>("destination");
+
+    QTest::newRow("http") << QUrl("http://QInvalidDomain.qt/test");
+    QTest::newRow("https") << QUrl("https://QInvalidDomain.qt/test");
+    QTest::newRow("ftp") << QUrl("ftp://QInvalidDomain.qt/test");
+    QTest::newRow("file") << QUrl("file:///thisfolderdoesn'texist/probably.txt");
+#ifdef Q_OS_WIN
+    // Only supported on windows.
+    QTest::newRow("remote-file") << QUrl("file://QInvalidHost/thisfolderdoesn'texist/probably.txt");
+#endif
+    QTest::newRow("qrc") << QUrl("qrc:///path/to/nowhere");
+    QTest::newRow("data") << QUrl("data:,Some%20plaintext%20data");
+}
+
+void tst_QNetworkReply::autoDeleteRepliesAttribute()
+{
+    QFETCH(QUrl, destination);
+    {
+        // Get
+        QNetworkRequest request(destination);
+        request.setAttribute(QNetworkRequest::AutoDeleteReplyOnFinishAttribute, true);
+        QNetworkReply *reply = manager.get(request);
+        QSignalSpy finishedSpy(reply, &QNetworkReply::finished);
+        QSignalSpy destroyedSpy(reply, &QObject::destroyed);
+        QVERIFY(finishedSpy.wait());
+        QCOMPARE(destroyedSpy.count(), 0);
+        QVERIFY(destroyedSpy.wait());
+    }
+    {
+        // Post
+        QNetworkRequest request(destination);
+        request.setAttribute(QNetworkRequest::AutoDeleteReplyOnFinishAttribute, true);
+        QNetworkReply *reply = manager.post(request, QByteArrayLiteral("datastring"));
+        QSignalSpy finishedSpy(reply, &QNetworkReply::finished);
+        QSignalSpy destroyedSpy(reply, &QObject::destroyed);
+        QVERIFY(finishedSpy.wait());
+        QCOMPARE(destroyedSpy.count(), 0);
+        QVERIFY(destroyedSpy.wait());
+    }
+    // Now repeated, but without the attribute to make sure it does not get deleted automatically.
+    // We need two calls to processEvents to test that the QNetworkReply doesn't get deleted.
+    // The first call executes a metacall event which adds the deleteLater meta event which
+    // would be executed in the second call. But that shouldn't happen without the attribute.
+    {
+        // Get
+        QNetworkRequest request(destination);
+        QScopedPointer<QNetworkReply> reply(manager.get(request));
+        QSignalSpy finishedSpy(reply.data(), &QNetworkReply::finished);
+        QSignalSpy destroyedSpy(reply.data(), &QObject::destroyed);
+        QVERIFY(finishedSpy.wait());
+        QCOMPARE(destroyedSpy.count(), 0);
+        QCoreApplication::processEvents();
+        QCoreApplication::processEvents();
+        QCOMPARE(destroyedSpy.count(), 0);
+    }
+    {
+        // Post
+        QNetworkRequest request(destination);
+        QScopedPointer<QNetworkReply> reply(manager.post(request, QByteArrayLiteral("datastring")));
+        QSignalSpy finishedSpy(reply.data(), &QNetworkReply::finished);
+        QSignalSpy destroyedSpy(reply.data(), &QObject::destroyed);
+        QVERIFY(finishedSpy.wait());
+        QCOMPARE(destroyedSpy.count(), 0);
+        QCoreApplication::processEvents();
+        QCoreApplication::processEvents();
+        QCOMPARE(destroyedSpy.count(), 0);
+    }
+}
+
 // NOTE: This test must be last testcase in tst_qnetworkreply!
 void tst_QNetworkReply::parentingRepliesToTheApp()
 {