Fix qml cache invalidation when changing dependent C++ registered QML singletons

When a qml file uses a qml singleton, we need to reliably detect when
the singleton changes and re-generate the cache of the qml file using
it. This is a scenario covered and fixed by commit
5b94de09cc738837d1539e28b3c0dccd17c18d29, with the exception that
currently QML singletons registered via qmlRegisterSingleton were not
added to the list of dependent singletons for a qml file. We can fix
this by extending findCompositeSingletons() to also cover the singletons
that do not originate from a qmldir file.

[ChangeLog][Qt][Qml] Fixed bug where sometimes changes to a qml
singleton would not propagate to the users or cause crashes.

Task-number: QTBUG-62243
Change-Id: I16c3d9ba65fd82e898a29b946c341907751135a9
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

3 files changed, 25 insertions, 0 deletions

diff --git a/src/qml/qml/qqmlimport.cpp b/src/qml/qml/qqmlimport.cpp
index 0bd7317470..ccd287e1b6 100644
--- a/src/qml/qml/qqmlimport.cpp
+++ b/src/qml/qml/qqmlimport.cpp
@@ -471,6 +471,17 @@ void findCompositeSingletons(const QQmlImportNamespace &set, QList<QQmlImports::
                 resultList.append(ref);
             }
         }
+
+        if (QQmlTypeModule *module = QQmlMetaType::typeModule(import->uri, import->majversion)) {
+            module->walkCompositeSingletons([&resultList, &set](const QQmlType &singleton) {
+                QQmlImports::CompositeSingletonReference ref;
+                ref.typeName = singleton.elementName();
+                ref.prefix = set.prefix;
+                ref.majorVersion = singleton.majorVersion();
+                ref.minorVersion = singleton.minorVersion();
+                resultList.append(ref);
+            });
+        }
     }
 }
 
diff --git a/src/qml/qml/qqmlmetatype.cpp b/src/qml/qml/qqmlmetatype.cpp
index 5bbc250d5e..8f5d11a96f 100644
--- a/src/qml/qml/qqmlmetatype.cpp
+++ b/src/qml/qml/qqmlmetatype.cpp
@@ -1258,6 +1258,18 @@ QQmlType QQmlTypeModule::type(const QV4::String *name, int minor) const
     return QQmlType();
 }
 
+void QQmlTypeModule::walkCompositeSingletons(const std::function<void(const QQmlType &)> &callback) const
+{
+    QMutexLocker lock(metaTypeDataLock());
+    for (auto typeCandidates = d->typeHash.begin(), end = d->typeHash.end();
+         typeCandidates != end; ++typeCandidates) {
+        for (auto type: typeCandidates.value()) {
+            if (type->regType == QQmlType::CompositeSingletonType)
+                callback(QQmlType(type));
+        }
+    }
+}
+
 QQmlTypeModuleVersion::QQmlTypeModuleVersion()
 : m_module(0), m_minor(0)
 {
diff --git a/src/qml/qml/qqmlmetatype_p.h b/src/qml/qml/qqmlmetatype_p.h
index ac2133ba30..9a7736ffcd 100644
--- a/src/qml/qml/qqmlmetatype_p.h
+++ b/src/qml/qml/qqmlmetatype_p.h
@@ -298,6 +298,8 @@ public:
     QQmlType type(const QHashedStringRef &, int) const;
     QQmlType type(const QV4::String *, int) const;
 
+    void walkCompositeSingletons(const std::function<void(const QQmlType &)> &callback) const;
+
     QQmlTypeModulePrivate *priv() { return d; }
 private:
     //Used by register functions and creates the QQmlTypeModule for them