Fix: mutable to immutable object conversion with python bindings

python/templates/MutableObject.cc.jinja2

@@ -17,7 +17,6 @@
 {{ utils.namespace_open(class.namespace) }}
 
 {{ macros.constructors_destructors(class.bare_type, Members, prefix='Mutable') }}
-Mutable{{ class.bare_type }}::operator {{ class.bare_type }}() const { return {{ class.bare_type }}(m_obj); }
 
 {{ macros.member_getters(class, Members, use_get_syntax, prefix='Mutable') }}
 {{ macros.single_relation_getters(class, OneToOneRelations, use_get_syntax, prefix='Mutable') }}

python/templates/MutableObject.h.jinja2

@@ -39,9 +39,6 @@ public:
 
 {{ macros.constructors_destructors(class.bare_type, Members, prefix='Mutable') }}
 
-  /// conversion to const object
-  operator {{ class.bare_type }}() const;
-
 public:
 
 {{ macros.member_getters(Members, use_get_syntax) }}

python/templates/Object.cc.jinja2

@@ -18,6 +18,8 @@
 
 {{ macros.constructors_destructors(class.bare_type, Members) }}
 
+{{ class.bare_type }}::{{ class.bare_type }}(const Mutable{{ class.bare_type }}& other): {{ class.bare_type }}(other.m_obj) {}
+
 {{ class.bare_type }}::{{ class.bare_type }}({{ class.bare_type }}Obj* obj) : m_obj(podio::utils::MaybeSharedPtr<{{ class.bare_type }}Obj>(obj)) {}
 
 {{ class.bare_type }} {{ class.bare_type }}::makeEmpty() {

python/templates/Object.h.jinja2

@@ -43,6 +43,8 @@ public:
   using collection_type = {{ class.bare_type }}Collection;
 
 {{ macros.constructors_destructors(class.bare_type, Members) }}
+  /// converting constructor from mutable object
+  {{ class.bare_type }}(const Mutable{{ class.bare_type }}& other);
 
   static {{ class.bare_type }} makeEmpty();
 

tests/unittests/CMakeLists.txt

@@ -94,3 +94,7 @@ else()
         PODIO_SIOBLOCK_PATH=${CMAKE_CURRENT_BINARY_DIR}
   )
 endif()
+
+add_test(NAME unittest.py COMMAND python3 ${CMAKE_CURRENT_SOURCE_DIR}/unittests.py)
+PODIO_SET_TEST_ENV(unittest.py)
+set_tests_properties(unittest.py PROPERTIES WORKING_DIRECTORY ${PROJECT_BINARY_DIR}/tests)

tests/unittests/unittests.py

@@ -0,0 +1,43 @@
+#!/usr/bin/env python3
+"""cppyy python binding tests"""
+
+import unittest
+import ROOT
+
+res = ROOT.gSystem.Load("libTestDataModel.so")
+if res < 0:
+    raise RuntimeError("Failed to load libTestDataModel.so")
+
+from ROOT import MutableExampleMC  # pylint: disable=wrong-import-position # noqa: E402
+from ROOT import ExampleMCCollection  # pylint: disable=wrong-import-position # noqa: E402
+
+
+class ObjectConversionsTest(unittest.TestCase):
+    """Object conversion binding tests"""
+
+    def test_conversion_mutable_to_immutable(self):
+        ROOT.gInterpreter.Declare(
+            """
+            void test_accepts_immutable(ExampleMC) {}
+            """
+        )
+        accepts_immutable = ROOT.test_accepts_immutable
+        mutable_obj = MutableExampleMC()
+        accepts_immutable(mutable_obj)
+
+
+class OneToManyRelationsTest(unittest.TestCase):
+    """OneToManyRelations binding tests"""
+
+    def test_add(self):
+        particles = ExampleMCCollection()
+        parent_particle = particles.create()
+        daughter_particle = particles.create()
+
+        self.assertEqual(len(daughter_particle.parents()), 0)
+        daughter_particle.addparents(parent_particle)
+        self.assertEqual(len(daughter_particle.parents()), 1)
+
+
+if __name__ == "__main__":
+    unittest.main()