QML TypeLoader: Sort composite singletons before recursing into them

When recursingly loading further types for composite singletons before
sorting them, the order in which the recursively referenced types are
loaded is random because the composite singletons are kept in an
(unordered) hash. Any sorting after loading the child components doesn't
help as the recursive references may depend on the types already loaded
at that point.

Sorting the composite singletons before starting the recursion does help
because it eliminates the source of randomness in the system.

Fixes: QTBUG-66976
Change-Id: I0fa1f50b36eba8c73eb8d56b4d5118485ab05f35
Reviewed-by: Michael Brasser <michael.brasser@live.com>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

2 files changed, 14 insertions, 4 deletions

diff --git a/src/qml/qml/qqmlimport.cpp b/src/qml/qml/qqmlimport.cpp
index bc53b98b5b..ab63489dbf 100644
--- a/src/qml/qml/qqmlimport.cpp
+++ b/src/qml/qml/qqmlimport.cpp
@@ -511,6 +511,20 @@ QList<QQmlImports::CompositeSingletonReference> QQmlImports::resolvedCompositeSi
         findCompositeSingletons(set, compositeSingletons, baseUrl());
     }
 
+    std::stable_sort(compositeSingletons.begin(), compositeSingletons.end(),
+                     [](const QQmlImports::CompositeSingletonReference &lhs,
+                        const QQmlImports::CompositeSingletonReference &rhs) {
+        if (lhs.prefix != rhs.prefix)
+            return lhs.prefix < rhs.prefix;
+
+        if (lhs.typeName != rhs.typeName)
+            return lhs.typeName < rhs.typeName;
+
+        return lhs.majorVersion != rhs.majorVersion
+            ? lhs.majorVersion < rhs.majorVersion
+            : lhs.minorVersion < rhs.minorVersion;
+    });
+
     return compositeSingletons;
 }
 
diff --git a/src/qml/qml/qqmltypeloader.cpp b/src/qml/qml/qqmltypeloader.cpp
index 7480475ca7..cb90af4cf0 100644
--- a/src/qml/qml/qqmltypeloader.cpp
+++ b/src/qml/qml/qqmltypeloader.cpp
@@ -2723,10 +2723,6 @@ void QQmlTypeData::resolveTypes()
         }
     }
 
-    std::stable_sort(m_compositeSingletons.begin(), m_compositeSingletons.end(), [](const TypeReference &lhs, const TypeReference &rhs){
-        return lhs.qualifiedName() < rhs.qualifiedName();
-    });
-
     for (QV4::CompiledData::TypeReferenceMap::ConstIterator unresolvedRef = m_typeReferences.constBegin(), end = m_typeReferences.constEnd();
          unresolvedRef != end; ++unresolvedRef) {