QV4Engine: Fix type conversion

When converting JS arrays to sequence<T> type, check first for the
existence of a QJSValue -> T converter function. This restores the
behavior from Qt <= 5.14. Amends ecdb4ed275a0869dc668d73d774735575d43a0a3

Fixes: QTBUG-84104
Change-Id: I14c86ab37e34a3c8cff072574d4b90fe9e558535
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

3 files changed, 39 insertions, 1 deletions

diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index b308737434..4d4013db48 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -1576,7 +1576,18 @@ static QVariant toVariant(QV4::ExecutionEngine *e, const QV4::Value &value, int
                 QV4::ScopedValue arrayValue(scope);
                 for (qint64 i = 0; i < length; ++i) {
                     arrayValue = a->get(i);
-                    QVariant asVariant = toVariant(e, arrayValue, retnAsIterable._metaType_id, false, visitedObjects);
+                    QVariant asVariant;
+                    if (QMetaType::hasRegisteredConverterFunction(qMetaTypeId<QJSValue>(), retnAsIterable._metaType_id)) {
+                        // before attempting a conversion from the concrete types,
+                        // check if there exists a conversion from QJSValue -> out type
+                        // prefer that one for compatibility reasons
+                        asVariant = QVariant::fromValue(QJSValuePrivate::fromReturnedValue(arrayValue->asReturnedValue()));
+                        if (asVariant.convert(retnAsIterable._metaType_id)) {
+                            retnAsIterable.append(asVariant.constData());
+                            continue;
+                        }
+                    }
+                    asVariant = toVariant(e, arrayValue, retnAsIterable._metaType_id, false, visitedObjects);
                     auto originalType = asVariant.userType();
                     bool couldConvert = asVariant.convert(retnAsIterable._metaType_id);
                     if (!couldConvert) {
diff --git a/tests/auto/qml/qqmllanguage/data/arrayToContainer.qml b/tests/auto/qml/qqmllanguage/data/arrayToContainer.qml
index d8e278a7a1..bc1b0d51e0 100644
--- a/tests/auto/qml/qqmllanguage/data/arrayToContainer.qml
+++ b/tests/auto/qml/qqmllanguage/data/arrayToContainer.qml
@@ -6,4 +6,5 @@ TestItem {
     property var myset
     positions: vector
     barrays: myset
+    convertibles: ["hello", "world"]
 }
diff --git a/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp b/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
index b4888f6fa7..77e545722a 100644
--- a/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
+++ b/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
@@ -5775,23 +5775,47 @@ void tst_qqmllanguage::inlineComponentDuplicateNameError()
     QCOMPARE(component.errorString(), message);
 }
 
+struct QJSValueConvertible {
+
+    Q_GADGET
+
+public:
+    QString msg;
+};
+
+bool operator==(const QJSValueConvertible &lhs, const QJSValueConvertible &rhs) {
+    return lhs.msg == rhs.msg;
+}
+
 class TestItem : public QObject
 {
     Q_OBJECT
     Q_PROPERTY( QVector<QPointF> positions MEMBER m_points  )
     Q_PROPERTY( QSet<QByteArray> barrays MEMBER m_barrays  )
+    Q_PROPERTY( QVector<QJSValueConvertible> convertibles MEMBER m_convertibles)
 
 public:
     TestItem() = default;
     QVector< QPointF > m_points;
     QSet<QByteArray> m_barrays;
+    QVector<QJSValueConvertible> m_convertibles;
 };
 
 
 Q_DECLARE_METATYPE(QVector<QPointF>);
 Q_DECLARE_METATYPE(QSet<QByteArray>);
+Q_DECLARE_METATYPE(QJSValueConvertible);
+Q_DECLARE_METATYPE(QVector<QJSValueConvertible>);
+
 void tst_qqmllanguage::arrayToContainer()
 {
+    QMetaType::registerConverter< QJSValue, QJSValueConvertible >(
+
+        [](const QJSValue& value)
+        {
+            return QJSValueConvertible{value.toString()};
+        }
+    );
     QQmlEngine engine;
     qmlRegisterType<TestItem>("qt.test", 1, 0, "TestItem");
     QVector<QPointF> points { QPointF (2.0, 3.0) };
@@ -5804,6 +5828,8 @@ void tst_qqmllanguage::arrayToContainer()
     QCOMPARE(root->m_points.at(0), QPointF (2.0, 3.0) );
     QVERIFY(root->m_barrays.contains("hello"));
     QVERIFY(root->m_barrays.contains("world"));
+    QCOMPARE(root->m_convertibles.at(0).msg, QLatin1String("hello"));
+    QCOMPARE(root->m_convertibles.at(1).msg, QLatin1String("world"));
 }
 
 class EnumTester : public QObject