QMetaObjectPrivate: Add firstMethod

QMetaObject::indexfOfMethod returns the method corresponding to a
specific signature. In QML, we however only want any of the methods with
a given name (and do overload resolution at a later point).
For this usecase this patch introduces the internal
QMetaObject::firstMethod function.

Change-Id: Ie3820354edffb273c4cbe1399201a955ebe79344
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/kernel/qmetaobject.cpp

@@ -590,6 +590,24 @@ bool QMetaObjectPrivate::methodMatch(const QMetaObject *m, const QMetaMethod &me
     return true;
 }
 
+/*!
+   \internal
+   Returns the first method with name \a name found in \a baseObject
+ */
+QMetaMethod QMetaObjectPrivate::firstMethod(const QMetaObject *baseObject, QByteArrayView name)
+{
+    for (const QMetaObject *currentObject = baseObject; currentObject; currentObject = currentObject->superClass()) {
+        const int start = priv(currentObject->d.data)->methodCount - 1;
+        const int end = 0;
+        for (int i = start; i >= end; --i) {
+            auto candidate = QMetaMethod::fromRelativeMethodIndex(currentObject, i);
+            if (name == candidate.name())
+                return candidate;
+        }
+    }
+    return QMetaMethod{};
+}
+
 /**
 * \internal
 * helper function for indexOf{Method,Slot,Signal}, returns the relative index of the method within

src/corelib/kernel/qmetaobject_p.h

@@ -253,6 +253,7 @@ struct QMetaObjectPrivate
     static bool methodMatch(const QMetaObject *m, const QMetaMethod &method,
                             const QByteArray &name, int argc,
                             const QArgumentType *types);
+    Q_CORE_EXPORT static QMetaMethod firstMethod(const QMetaObject *baseObject, QByteArrayView name);
 
 };
 

tests/auto/corelib/kernel/qmetaobject/tst_qmetaobject.cpp

@@ -321,6 +321,9 @@ private slots:
     void indexOfMethod_data();
     void indexOfMethod();
 
+    void firstMethod_data();
+    void firstMethod();
+
     void indexOfMethodPMF();
 
     void signalOffset_data();
@@ -1700,6 +1703,42 @@ void tst_QMetaObject::indexOfMethod()
     QCOMPARE(object->metaObject()->indexOfSignal(name), !isSignal ? -1 : idx);
 }
 
+class Base : public QObject {
+    Q_OBJECT
+public slots:
+    int test() {return 0;}
+    int baseOnly() {return 0;}
+};
+
+class Derived : public Base {
+    Q_OBJECT
+
+public slots:
+    int test() {return 1;}
+};
+
+void tst_QMetaObject::firstMethod_data()
+{
+    QTest::addColumn<QByteArray>("name");
+    QTest::addColumn<QMetaMethod>("method");
+
+    const QMetaObject &derived = Derived::staticMetaObject;
+    const QMetaObject &base = Base::staticMetaObject;
+
+    QTest::newRow("own method") << QByteArray("test") << derived.method(derived.indexOfMethod("test()"));
+    QTest::newRow("parent method") << QByteArray("baseOnly") << derived.method(base.indexOfMethod("baseOnly()"));
+    QTest::newRow("invalid") << QByteArray("invalid") << QMetaMethod();
+}
+
+void tst_QMetaObject::firstMethod()
+{
+    QFETCH(QByteArray, name);
+    QFETCH(QMetaMethod, method);
+
+    QMetaMethod firstMethod = QMetaObjectPrivate::firstMethod(&Derived::staticMetaObject, name);
+    QCOMPARE(firstMethod, method);
+}
+
 void tst_QMetaObject::indexOfMethodPMF()
 {
 #define INDEXOFMETHODPMF_HELPER(ObjectType, Name, Arguments)  { \