Fix exposure of -1 as enum value in QML exposed C++ singletons

When a C++ singleton has an enum with the value -1, we would expose that
value correctly when taking the accelerated property access code path in
the optimizer, but when going through the slower QQmlTypeWrapper we
would return undefined. This turned out to be a silly logic error that
assumed that -1 is not a valid value for an enum and instead indicates
an enum value not present.

[ChangeLog][Qml] Fix -1 as enum value in QML exposed C++ singletons
showing up as undefined.

Task-number: QTBUG-66067
Change-Id: Ib66dad7a4b59822b2c40ad6bd9af4b72469582e9
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Michael Brasser <michael.brasser@live.com>

1 files changed, 12 insertions, 10 deletions

diff --git a/src/qml/qml/qqmltypewrapper.cpp b/src/qml/qml/qqmltypewrapper.cpp
index d4e1910a72..0fae76066d 100644
--- a/src/qml/qml/qqmltypewrapper.cpp
+++ b/src/qml/qml/qqmltypewrapper.cpp
@@ -133,11 +133,11 @@ ReturnedValue QmlTypeWrapper::create(QV4::ExecutionEngine *engine, QObject *o, Q
 }
 
 static int enumForSingleton(QV4::ExecutionEngine *v4, String *name, QObject *qobjectSingleton,
-                            const QQmlType &type)
+                            const QQmlType &type, bool *ok)
 {
-    bool ok;
-    int value = type.enumValue(QQmlEnginePrivate::get(v4->qmlEngine()), name, &ok);
-    if (ok)
+    Q_ASSERT(ok != nullptr);
+    int value = type.enumValue(QQmlEnginePrivate::get(v4->qmlEngine()), name, ok);
+    if (*ok)
         return value;
 
     // ### Optimize
@@ -145,10 +145,11 @@ static int enumForSingleton(QV4::ExecutionEngine *v4, String *name, QObject *qob
     const QMetaObject *metaObject = qobjectSingleton->metaObject();
     for (int ii = metaObject->enumeratorCount() - 1; ii >= 0; --ii) {
         QMetaEnum e = metaObject->enumerator(ii);
-        value = e.keyToValue(enumName.constData(), &ok);
-        if (ok)
+        value = e.keyToValue(enumName.constData(), ok);
+        if (*ok)
             return value;
     }
+    *ok = false;
     return -1;
 }
 
@@ -191,8 +192,9 @@ ReturnedValue QmlTypeWrapper::get(const Managed *m, String *name, bool *hasPrope
                 // check for enum value
                 const bool includeEnums = w->d()->mode == Heap::QmlTypeWrapper::IncludeEnums;
                 if (includeEnums && name->startsWithUpper()) {
-                    const int value = enumForSingleton(v4, name, qobjectSingleton, type);
-                    if (value != -1)
+                    bool ok = false;
+                    const int value = enumForSingleton(v4, name, qobjectSingleton, type, &ok);
+                    if (ok)
                         return QV4::Primitive::fromInt32(value).asReturnedValue();
                 }
 
@@ -204,8 +206,8 @@ ReturnedValue QmlTypeWrapper::get(const Managed *m, String *name, bool *hasPrope
 
                 // Warn when attempting to access a lowercased enum value, singleton case
                 if (!ok && includeEnums && !name->startsWithUpper()) {
-                    const int value = enumForSingleton(v4, name, qobjectSingleton, type);
-                    if (value != -1)
+                    enumForSingleton(v4, name, qobjectSingleton, type, &ok);
+                    if (ok)
                         return throwLowercaseEnumError(v4, name, type);
                 }