Implement multiple inheritance correctly, compatible version

PySide does not implement multiple inheritance.
Please see "About Multiple Inheritance in Python" at the issue.

This patch just supports the `__init__` call.
A more consequent implementation will follow that
supports multiple inheritance with every method.

[ChangeLog][pyside6] Cooperative multiple inheritance is now
implemented for all __init__ methods.

Fixes: PYSIDE-1564
Change-Id: I8df805d22c2052c3a9747420a86341f64e29a5ad
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 13 insertions, 6 deletions

diff --git a/sources/shiboken6/generator/shiboken/cppgenerator.cpp b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
index 63fc65f19..8563aec8e 100644
--- a/sources/shiboken6/generator/shiboken/cppgenerator.cpp
+++ b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
@@ -2297,11 +2297,12 @@ void CppGenerator::writeMethodWrapperPreamble(TextStream &s,const OverloadData &
         initPythonArguments = minArgs != maxArgs || maxArgs > 1;
     }
 
-    if (needsArgumentErrorHandling(overloadData)) {
-        s << R"(Shiboken::AutoDecRef errInfo{};
-static const char fullName[] = ")" << fullPythonFunctionName(rfunc, true)
-            << "\";\nSBK_UNUSED(fullName)\n";
-    }
+    if (needsArgumentErrorHandling(overloadData))
+        s << "Shiboken::AutoDecRef errInfo{};\n";
+
+    s << "static const char fullName[] = \"" << fullPythonFunctionName(rfunc, true)
+        << "\";\nSBK_UNUSED(fullName)\n";
+
     if (maxArgs > 0) {
         s << "int overloadId = -1;\n"
             << PYTHON_TO_CPPCONVERSION_STRUCT << ' ' << PYTHON_TO_CPP_VAR;
@@ -2389,6 +2390,12 @@ void CppGenerator::writeConstructorWrapper(TextStream &s, const OverloadData &ov
     if (overloadData.maxArgs() > 0)
         writeOverloadedFunctionDecisor(s, overloadData, errorReturn);
 
+    // Handles Python Multiple Inheritance
+    QString pre = needsMetaObject ? u"bool usesPyMI = "_s : u""_s;
+    s << "\n// PyMI support\n"
+        << pre << "Shiboken::callInheritedInit(self, args, kwds, fullName);\n"
+        << "if (PyErr_Occurred())\n" << indent << errorReturn << outdent << "\n";
+
     writeFunctionCalls(s, overloadData, classContext, errorReturn);
     s << '\n';
 
@@ -2423,7 +2430,7 @@ void CppGenerator::writeConstructorWrapper(TextStream &s, const OverloadData &ov
             << "PySide::Signal::updateSourceObject(self);\n"
             << "metaObject = cptr->metaObject(); // <- init python qt properties\n"
             << "if (!errInfo.isNull() && PyDict_Check(errInfo.object())) {\n" << indent
-                << "if (!PySide::fillQtProperties(self, metaObject, errInfo))\n" << indent
+                << "if (!PySide::fillQtProperties(self, metaObject, errInfo, usesPyMI))\n" << indent
                     << "return " << returnErrorWrongArguments(overloadData, errorReturn) << ";\n"
                     << outdent << outdent
             << "};\n";