QML: Only release types if they aren't referenced anymorev5.7.0

Just checking for references on m_compiledData is not enough. The
actual component can also be referenced. Thus it won't be deleted
on release(), but cannot be found in the type cache anymore.

Task-number: QTBUG-53761
(cherry picked from commit 2ac19881f92c94f4e9427bd9ff513210675f259e)
Change-Id: If254d5bca1f41ec948ec1438df0d37bf8d531bdf
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

2 files changed, 14 insertions, 4 deletions

diff --git a/src/qml/qml/qqmltypeloader.cpp b/src/qml/qml/qqmltypeloader.cpp
index 29fdf78797..739a833a30 100644
--- a/src/qml/qml/qqmltypeloader.cpp
+++ b/src/qml/qml/qqmltypeloader.cpp
@@ -1950,7 +1950,8 @@ void QQmlTypeLoader::trimCache()
         QList<TypeCache::Iterator> unneededTypes;
         for (TypeCache::Iterator iter = m_typeCache.begin(), end = m_typeCache.end(); iter != end; ++iter)  {
             QQmlTypeData *typeData = iter.value();
-            if (typeData->m_compiledData && typeData->m_compiledData->count() == 1) {
+            if (typeData->m_compiledData && typeData->count() == 1
+                    && typeData->m_compiledData->count() == 1) {
                 // There are no live objects of this type
                 unneededTypes.append(iter);
             }
diff --git a/tests/auto/qml/qqmltypeloader/tst_qqmltypeloader.cpp b/tests/auto/qml/qqmltypeloader/tst_qqmltypeloader.cpp
index ef1ea3a897..3e8e1d23ea 100644
--- a/tests/auto/qml/qqmltypeloader/tst_qqmltypeloader.cpp
+++ b/tests/auto/qml/qqmltypeloader/tst_qqmltypeloader.cpp
@@ -81,10 +81,19 @@ void tst_QQMLTypeLoader::trimCache()
         url.setQuery(QString::number(i));
 
         QQmlTypeData *data = loader.getType(url);
-        if (i % 5 == 0) // keep references to some of them so that they aren't trimmed
-            data->compiledData()->addref();
+        // Run an event loop to receive the callback that release()es.
+        QTRY_COMPARE(data->count(), 2);
 
-        data->release();
+        // keep references to some of them so that they aren't trimmed. References to either the
+        // QQmlTypeData or its compiledData() should prevent the trimming.
+        if (i % 10 == 0) {
+            // keep ref on data, don't add ref on data->compiledData()
+        } else if (i % 5 == 0) {
+            data->compiledData()->addref();
+            data->release();
+        } else {
+            data->release();
+        }
     }
 
     for (int i = 0; i < 256; ++i) {