3 files changed, 35 insertions, 6 deletions
diff --git a/sources/pyside6/tests/QtWidgets/qlayout_test.py b/sources/pyside6/tests/QtWidgets/qlayout_test.py
index 72eb586a1..cc41f78b1 100644
--- a/sources/pyside6/tests/QtWidgets/qlayout_test.py
+++ b/sources/pyside6/tests/QtWidgets/qlayout_test.py
@@ -127,6 +127,13 @@ class QLayoutTest(UsesQApplication):
         gc.collect()
         self.assertRaises(RuntimeError, spacer.isEmpty)
 
+    def testConstructorProperties(self):
+        """PYSIDE-1986, test passing properties to the constructor of
+           QHBoxLayout, which does not have default arguments."""
+        layout = QHBoxLayout(objectName="layout", spacing=30)
+        self.assertEqual(layout.spacing(), 30)
+        self.assertEqual(layout.objectName(), "layout")
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/sources/shiboken6/generator/shiboken/cppgenerator.cpp b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
index 1878dd4d9..99cac73d0 100644
--- a/sources/shiboken6/generator/shiboken/cppgenerator.cpp
+++ b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
@@ -3595,11 +3595,32 @@ void CppGenerator::writeSetPythonToCppPointerConversion(TextStream &s,
                               converterVar, pythonToCppFunc, isConvertibleFunc);
 }
 
+// PYSIDE-1986: Some QObject derived classes, (QVBoxLayout) do not have default
+// arguments, which breaks setting properties by named arguments. Force the
+// handling code to be generated nevertheless for applicable widget classes,
+// so that the mechanism of falling through to the error handling to set
+// the properties works nevertheless.
+static bool forceQObjectNamedArguments(const AbstractMetaFunctionCPtr &func)
+{
+    if (func->functionType() != AbstractMetaFunction::ConstructorFunction)
+        return false;
+    auto *owner = func->ownerClass();
+    Q_ASSERT(owner);
+    if (!owner->isQObject())
+        return false;
+    const QString &name = owner->name();
+    return name == u"QVBoxLayout" || name == u"QHBoxLayout"
+        || name == u"QSplitterHandle" || name == u"QSizeGrip";
+}
+
 void CppGenerator::writeNamedArgumentResolution(TextStream &s, const AbstractMetaFunctionCPtr &func,
-                                                bool usePyArgs, const OverloadData &overloadData)
+                                                bool usePyArgs, const OverloadData &overloadData) const
 {
     const AbstractMetaArgumentList &args = OverloadData::getArgumentsWithDefaultValues(func);
-    if (args.isEmpty()) {
+    const bool hasDefaultArguments = !args.isEmpty();
+    const bool force = !hasDefaultArguments && usePySideExtensions()
+        && forceQObjectNamedArguments(func);
+    if (!hasDefaultArguments && !force) {
         if (overloadData.hasArgumentWithDefaultValue()) {
             // PySide-535: Allow for empty dict instead of nullptr in PyPy
             s << "if (kwds && PyDict_Size(kwds) > 0) {\n";
@@ -3618,8 +3639,9 @@ void CppGenerator::writeNamedArgumentResolution(TextStream &s, const AbstractMet
     s << "if (kwds && PyDict_Size(kwds) > 0) {\n";
     {
         Indentation indent(s);
-        s << "PyObject *value{};\n"
-            << "Shiboken::AutoDecRef kwds_dup(PyDict_Copy(kwds));\n";
+        if (!force)
+            s << "PyObject *value{};\n";
+        s << "Shiboken::AutoDecRef kwds_dup(PyDict_Copy(kwds));\n";
         for (const AbstractMetaArgument &arg : args) {
             const int pyArgIndex = arg.argumentIndex()
                 - OverloadData::numberOfRemovedArguments(func, arg.argumentIndex());
diff --git a/sources/shiboken6/generator/shiboken/cppgenerator.h b/sources/shiboken6/generator/shiboken/cppgenerator.h
index a989fe35f..4d7f4e7c2 100644
--- a/sources/shiboken6/generator/shiboken/cppgenerator.h
+++ b/sources/shiboken6/generator/shiboken/cppgenerator.h
@@ -331,8 +331,8 @@ private:
                                               const QString &pythonToCppFunc,
                                               const QString &isConvertibleFunc);
 
-    static void writeNamedArgumentResolution(TextStream &s, const AbstractMetaFunctionCPtr &func,
-                                             bool usePyArgs, const OverloadData &overloadData);
+    void writeNamedArgumentResolution(TextStream &s, const AbstractMetaFunctionCPtr &func,
+                                      bool usePyArgs, const OverloadData &overloadData) const;
 
     /// Returns a string containing the name of an argument for the given function and argument index.
     static QString argumentNameFromIndex(const ApiExtractorResult &api,