QQuickLoader: make sure the status property change properly

Since the invocation of [setSource] in qml will clear the old source url
first, it is hard to decide whether we have changed the source url,
especially when we call [setSource] with an empty string, and the loader's
status won't change properly.

Fixes: QTBUG-85938
Change-Id: If61a33c790a4fd6562611c4c50756bc5e213363a
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 3aa4cd682f52b70803cc3f72d732bde9987677dd)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 39 insertions, 0 deletions

diff --git a/src/quick/items/qquickloader.cpp b/src/quick/items/qquickloader.cpp
index e1d533f092..e961617505 100644
--- a/src/quick/items/qquickloader.cpp
+++ b/src/quick/items/qquickloader.cpp
@@ -589,8 +589,15 @@ void QQuickLoader::setSource(QQmlV4Function *args)
     if (ipvError)
         return;
 
+    // 1. If setSource is called with a valid url, clear the old component and its corresponding url
+    // 2. If setSource is called with an invalid url(e.g. empty url), clear the old component but
+    // hold the url for old one.(we will compare it with new url later and may update status of loader to Loader.Null)
+    QUrl oldUrl = d->source;
     d->clear();
     QUrl sourceUrl = d->resolveSourceUrl(args);
+    if (!sourceUrl.isValid())
+        d->source = oldUrl;
+
     d->disposeInitialPropertyValues();
     if (!ipv->isUndefined()) {
         d->initialPropertyValues.set(args->v4engine(), ipv);
diff --git a/tests/auto/quick/qquickloader/data/setSourceAndCheckStatus.qml b/tests/auto/quick/qquickloader/data/setSourceAndCheckStatus.qml
new file mode 100644
index 0000000000..70779047aa
--- /dev/null
+++ b/tests/auto/quick/qquickloader/data/setSourceAndCheckStatus.qml
@@ -0,0 +1,14 @@
+import QtQuick 2.12
+import QtQuick.Window 2.12
+
+Window {
+    id: root
+    visible: true; width: 640; height: 480
+    Loader {
+        id: loader
+        anchors.fill: parent
+        function load(url) {
+            loader.setSource(url)
+        }
+    }
+}
diff --git a/tests/auto/quick/qquickloader/tst_qquickloader.cpp b/tests/auto/quick/qquickloader/tst_qquickloader.cpp
index 91d0bcab2e..91b42690cd 100644
--- a/tests/auto/quick/qquickloader/tst_qquickloader.cpp
+++ b/tests/auto/quick/qquickloader/tst_qquickloader.cpp
@@ -130,6 +130,8 @@ private slots:
     void sourceURLKeepComponent();
 
     void statusChangeOnlyEmittedOnce();
+
+    void setSourceAndCheckStatus();
 };
 
 Q_DECLARE_METATYPE(QList<QQmlError>)
@@ -1470,6 +1472,22 @@ void tst_QQuickLoader::statusChangeOnlyEmittedOnce()
     QCOMPARE(root->property("statusChangedCounter").toInt(), 2); // 1xLoading + 1xReady*/
 }
 
+void tst_QQuickLoader::setSourceAndCheckStatus()
+{
+    QQmlApplicationEngine engine;
+    auto url = testFileUrl("setSourceAndCheckStatus.qml");
+    engine.load(url);
+    auto root = engine.rootObjects().at(0);
+    QVERIFY(root);
+
+    QQuickLoader *loader = root->findChild<QQuickLoader *>();
+    QMetaObject::invokeMethod(loader, "load", Q_ARG(QVariant, QVariant::fromValue(QStringLiteral("./RedRect.qml"))));
+    QCOMPARE(loader->status(), QQuickLoader::Ready);
+
+    QMetaObject::invokeMethod(loader, "load", Q_ARG(QVariant, QVariant::fromValue(QStringLiteral(""))));
+    QCOMPARE(loader->status(), QQuickLoader::Null);
+}
+
 QTEST_MAIN(tst_QQuickLoader)
 
 #include "tst_qquickloader.moc"