partially fix features

src/dabmodel/__init__.py

@@ -13,6 +13,7 @@ Main module __init__ file.
 from .__metadata__ import __version__, __Summuary__, __Name__
 from .model import (
     DABFieldInfo,
+    DABField,
     BaseAppliance,
     BaseFeature,
     DABModelException,
@@ -27,4 +28,6 @@ from .model import (
     IncompletelyAnnotatedField,
     ImportForbidden,
     FunctionForbidden,
+    FrozenDABField,
+    InvalidFeatureInheritance,
 )

src/dabmodel/model.py

@@ -55,7 +55,6 @@ ALLOWED_ANNOTATIONS = {
 }
 
 ALLOWED_MODEL_FIELDS_TYPES = (str, int, float, complex, bool, bytes)
-ALLOWED_MODEL_FIELDS_CONTAINERS = (dict, list, set, frozenset, tuple)
 
 
 # TV_ALLOWED_MODEL_FIELDS_TYPES = TypeVar("TV_ALLOWED_MODEL_FIELDS_TYPES", *ALLOWED_MODEL_FIELDS_TYPES, *ALLOWED_MODEL_FIELDS_CONTAINERS)
@@ -66,7 +65,11 @@ class DABModelException(Exception):
     Base Exception for DABModelException class
     """
 
-
+class ReservedFieldName(Exception):
+    """DABModelException Exception class
+    Base Exception for DABModelException class
+    """
+    
 class MultipleInheritanceForbidden(DABModelException):
     """MultipleInheritanceForbidden Exception class
     Multiple inheritance is forbidden when using dabmodel
@@ -138,6 +141,10 @@ class ImportForbidden(DABModelException):
     Imports are forbidden
     """
 
+class InvalidFeatureInheritance(DABModelException):
+    """InvalidFeatureInheritance Exception class
+    Features of same name in child appliance need to be from same type
+    """
 
 class FunctionForbidden(DABModelException):
     """FunctionForbidden Exception class
@@ -298,7 +305,7 @@ class DABFieldInfo:
             self._constraints = constraints
 
     @property
-    def doc(self):
+    def doc(self) -> str:
         """Returns Field's documentation"""
         return self._doc
 
@@ -325,7 +332,7 @@ class DABField(Generic[T_Field]):
         self._source = s
 
     @property
-    def doc(self):
+    def doc(self) -> str:
         """Returns Field's documentation"""
         return self._info.doc
 
@@ -403,10 +410,14 @@ class ModelSpecView:
 
     __slots__ = ("_vals", "_types", "_touched", "_name", "_module")
 
-    def __init__(self, values: dict, types_map: dict[str, type], name, module):
+    def __init__(self, values: dict[str, Any], types_map: dict[str, type], name: str, module: str):
+        self._name: str
+        self._vals: dict[str, Any]
+        self._types: dict[str, type]
+        self._touched: set
+        self._module: str
         object.__setattr__(self, "_vals", dict(values))
         object.__setattr__(self, "_types", types_map)
-        object.__setattr__(self, "_touched", set())
         object.__setattr__(self, "_name", name)
         object.__setattr__(self, "_module", module)
 
@@ -421,16 +432,16 @@ class ModelSpecView:
         return self._module
 
     @__module__.setter
-    def __module__(self, value):
+    def __module__(self, value: str):
         pass
 
-    def __getattr__(self, name):
+    def __getattr__(self, name: str) -> Any:
         """internal proxy getattr"""
         if name not in self._types:
             raise AttributeError(f"Unknown field {name}")
         return self._vals[name]
 
-    def __setattr__(self, name, value):
+    def __setattr__(self, name: str, value: Any):
         """internal proxy setattr"""
         if name not in self._types:
             raise NonExistingField(f"Cannot set unknown field {name}")
@@ -446,7 +457,6 @@ class ModelSpecView:
             raise InvalidFieldValue(f"Field <{name}> value is not of expected type {T}.") from exp
 
         self._vals[name] = value
-        self._touched.add(name)
 
     def export(self) -> dict:
         """exports all proxified values"""
@@ -470,7 +480,7 @@ class BaseMeta(type):
         mcs: type["BaseMeta"], name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any]  # pylint: disable=unused-argument
     ) -> None:
         """early BaseElement checks"""
-        # print("__NEW__ Defining:", name, "with keys:", list(namespace))
+        print("__NEW__ Defining:", name, "with keys:", list(namespace))
 
         if len(bases) > 1:
             raise MultipleInheritanceForbidden("Multiple inheritance is not supported by dabmodel")
@@ -489,13 +499,46 @@ class BaseMeta(type):
                 namespace[_funknown] = None
 
     @classmethod
-    def pre_processing_modified(
+    def pre_processing(mcs: type["BaseMeta"], name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any]):
+        """preprocessing BaseElement"""
+        # iterating new and modified fields
+        mcs.modified_field = {}
+        mcs.new_fields = {}
+        mcs.initializer = None
+        initializer_name: Optional[str] = None
+        for _fname, _fvalue in namespace.items():
+            if _fname == f"_{name}__initializer" or (name.startswith("_") and _fname == "__initializer"):
+                if not isinstance(_fvalue, classmethod):
+                    raise InvalidInitializerType()
+                mcs.initializer = _fvalue.__func__
+                if name.startswith("_"):
+                    initializer_name = "__initializer"
+                else:
+                    initializer_name = f"_{name}__initializer"
+            elif _fname.startswith("__"):
+                pass
+            else:
+                # print(f"Parsing Field: {_fname} / {_fvalue}")
+                if len(bases) == 1 and _fname in namespace["__DABSchema__"].keys():  # Modified fields
+                    mcs.pre_processing_modified_fields(name, bases, namespace, _fname, _fvalue)
+                else:  # New fieds
+                    mcs.pre_processing_new_fields(name, bases, namespace, _fname, _fvalue)
+        # removing modified fields from class (will add them back later)
+        for _fname in mcs.new_fields:
+            del namespace[_fname]
+        for _fname in mcs.modified_field:
+            del namespace[_fname]
+        if mcs.initializer is not None and initializer_name is not None:
+            del namespace[initializer_name]
+
+    @classmethod
+    def pre_processing_modified_fields(
         mcs: type["BaseMeta"], name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any], _fname: str, _fvalue: Any
     ):  # pylint: disable=unused-argument
         """preprocessing BaseElement modified Fields"""
-        # print(f"Modified field: {_fname}")
+        print(f"Modified field: {_fname}")
         if "__annotations__" in namespace and _fname in namespace["__annotations__"]:
-            raise ReadOnlyFieldAnnotation("annotations cannot be modified on derived classes")
+            raise ReadOnlyFieldAnnotation(f"annotations cannot be modified on derived classes {_fname}")
         try:
             check_type(
                 _fvalue,
@@ -509,11 +552,11 @@ class BaseMeta(type):
         mcs.modified_field[_fname] = _fvalue
 
     @classmethod
-    def pre_processing_new(
+    def pre_processing_new_fields(
         mcs: type["BaseMeta"], name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any], _fname: str, _fvalue: Any
     ):  # pylint: disable=unused-argument
         """preprocessing BaseElement new Fields"""
-        # print(f"New field: {_fname}")
+        print(f"New field: {_fname}")
         # print(f"type is: {type(_fvalue)}")
         # print(f"value is: {_fvalue}")
 
@@ -540,8 +583,7 @@ class BaseMeta(type):
                     raise InvalidFieldAnnotation("Only DABFieldInfo object is allowed as Annotated data.")
 
                 _finfo = args[1]
-
-        # print(f"annotation is: {namespace['__annotations__'][_fname]}")
+                
         # check if value is valid
         try:
             check_type(_fvalue, namespace["__annotations__"][_fname], collection_check_strategy=CollectionCheckStrategy.ALL_ITEMS)
@@ -549,50 +591,18 @@ class BaseMeta(type):
             raise InvalidFieldValue(f"Value of Field <{_fname}> is not of expected type {namespace['__annotations__'][_fname]}.") from exp
         mcs.new_fields[_fname] = DABField(_fname, _fvalue, namespace["__annotations__"][_fname], _finfo)
 
-    @classmethod
-    def pre_processing(mcs: type["BaseMeta"], name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any]):
-        """preprocessing BaseElement"""
-        # iterating new and modified fields
-        mcs.modified_field = {}
-        mcs.new_fields = {}
-        mcs.initializer = None
-        initializer_name: Optional[str] = None
-        for _fname, _fvalue in namespace.items():
-            if _fname == f"_{name}__initializer" or (name.startswith("_") and _fname == "__initializer"):
-                if not isinstance(_fvalue, classmethod):
-                    raise InvalidInitializerType()
-                mcs.initializer = _fvalue.__func__
-                if name.startswith("_"):
-                    initializer_name = "__initializer"
-                else:
-                    initializer_name = f"_{name}__initializer"
-            elif _fname.startswith("__"):
-                pass
-            else:
-                # print(f"Parsing Field: {_fname} / {_fvalue}")
-                if len(bases) == 1 and _fname in namespace["__DABSchema__"].keys():  # Modified fields
-                    mcs.pre_processing_modified(name, bases, namespace, _fname, _fvalue)
-                else:  # New fieds
-                    mcs.pre_processing_new(name, bases, namespace, _fname, _fvalue)
-        # removing modified fields from class (will add them back later)
-        for _fname in mcs.new_fields:
-            del namespace[_fname]
-        for _fname in mcs.modified_field:
-            del namespace[_fname]
-        if mcs.initializer is not None and initializer_name is not None:
-            del namespace[initializer_name]
-
     @classmethod
     def call_initializer(
-        mcs: type["BaseMeta"], cls, name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any]
-    ):  # pylint: disable=unused-argument
+        mcs: type["BaseMeta"], cls, name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any]  # pylint: disable=unused-argument
+    ):
         """BaseElement initializer processing"""
         if mcs.initializer is not None:
             init_fieldvalues = {}
             init_fieldtypes = {}
             for _fname, _fvalue in cls.__DABSchema__.items():
-                init_fieldvalues[_fname] = deepcopy(_fvalue.raw_value)
-                init_fieldtypes[_fname] = _fvalue.annotations
+                if isinstance(_fvalue,DABField):
+                    init_fieldvalues[_fname] = deepcopy(_fvalue.raw_value)
+                    init_fieldtypes[_fname] = _fvalue.annotations
             fakecls = ModelSpecView(init_fieldvalues, init_fieldtypes, cls.__name__, cls.__module__)
             safe_globals = {"__builtins__": {"__import__": _blocked_import}, **ALLOWED_HELPERS_DEFAULT}
             if mcs.initializer.__code__.co_freevars:
@@ -613,69 +623,149 @@ class BaseMeta(type):
                         f"Value of Field <{_fname}> is not of expected type {namespace['__annotations__'][_fname]}."
                     ) from exp
                 cls.__DABSchema__[_fname].update_value(_fvalue)
-
+                
     def __new__(mcs: type["BaseMeta"], name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any]) -> Type:
         """BaseElement new class"""
         mcs.pre_check(name, bases, namespace)
         mcs.pre_processing(name, bases, namespace)
-
-        orig_setattr = namespace.get("__setattr__", object.__setattr__)
-
-        def guarded_setattr(self, key, value):
-            if key.startswith("_"):  # allow private and dunder attrs
-                return orig_setattr(self, key, value)
-            # block writes after init if key is readonly
-            if key in self.__DABSchema__.keys():
-                if hasattr(self, key):
-                    raise ReadOnlyField(f"{key} is read-only")
-            else:
-                raise NewFieldForbidden("creating new fields is not allowed")
-
-            return orig_setattr(self, key, value)
-
-        namespace["__setattr__"] = guarded_setattr
-
+               
         _cls = super().__new__(mcs, name, bases, namespace)
 
+        mcs.save_values(_cls, name, bases, namespace)
+        mcs.call_initializer(_cls, name, bases, namespace)
+        _cls.install_guard()
+        
+        return _cls
+    
+    @classmethod
+    def save_values(
+        mcs: type["BaseMeta"], cls, name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any]  # pylint: disable=unused-argument
+    ):
         for _fname, _fvalue in mcs.modified_field.items():
-            _cls.__DABSchema__[_fname] = deepcopy(bases[0].__DABSchema__[_fname])
-            _cls.__DABSchema__[_fname].update_value(_fvalue)
+            cls.__DABSchema__[_fname] = deepcopy(bases[0].__DABSchema__[_fname])
+            cls.__DABSchema__[_fname].update_value(_fvalue)
 
         for _fname, _fvalue in mcs.new_fields.items():
             _fvalue.add_source(mcs)
-            _cls.__DABSchema__[_fname] = _fvalue
-
-        mcs.call_initializer(_cls, name, bases, namespace)
-
-        return _cls
-
-    def __call__(cls, *args: Any, **kw: Any):  # intentionally untyped
+            cls.__DABSchema__[_fname] = _fvalue
+            
+    def __call__(cls: Type, *args: Any, **kw: Any):  # intentionally untyped
         """BaseElement new instance"""
         obj = super().__call__(*args, **kw)
 
         for _fname, _fvalue in cls.__DABSchema__.items():
-            setattr(obj, _fname, cls.__DABSchema__[_fname].value)
-        inst_schema: dict[str, Any] = {}
-        for _fname, _fvalue in cls.__DABSchema__.items():
-            inst_schema[_fname] = FrozenDABField(_fvalue)
-        setattr(obj, "__DABSchema__", inst_schema)
-        return obj
+            if isinstance(_fvalue,DABField):
+                object.__setattr__(obj, _fname, _fvalue.value)
 
+        inst_schema = copy(obj.__DABSchema__)
+        for _fname, _fvalue in cls.__DABSchema__.items():
+            if isinstance(_fvalue,DABField):
+                inst_schema[_fname] = FrozenDABField(_fvalue)
+                
+        object.__setattr__(obj, "__DABSchema__", inst_schema)
+        cls.modify_object(obj)
+        
+        
+        return obj
+    
+    def modify_object(cls:Type,obj):
+        pass
+    
+    
+    def install_guard(cls:Type):
+        orig_setattr = getattr(cls,"__setattr__")
+        
+        # cls.orig_setattr = orig_setattr
+        
+        def guarded_setattr(_self, key: str, value: Any):
+            if key.startswith("_"):  # allow private and dunder attrs
+                return orig_setattr(_self, key, value)
+            # block writes after init if key is readonly
+            if key in _self.__DABSchema__.keys():
+                if key in _self.__dict__:
+                    raise ReadOnlyField(f"{key} is read-only")
+            elif key in _self.__DABSchema__["features"].keys():
+                if key in _self.__dict__:
+                    raise ReadOnlyField(f"{key} is read-only")
+            else:
+                raise NewFieldForbidden("creating new fields is not allowed")
+
+            return orig_setattr(_self, key, value)
+
+        setattr(cls, "__setattr__", guarded_setattr)
 
 class BaseElement(metaclass=BaseMeta):
     """BaseElement class
     Base class to apply metaclass and set common Fields.
     """
 
+class BaseMetaFeature(BaseMeta):
+    pass
 
-class BaseFeature(BaseElement):
+class BaseFeature(BaseElement,metaclass=BaseMetaFeature):
     """BaseFeature class
     Base class for Appliance's Features.
     Features are optional traits of an appliance.
     """
+    Enabled:bool=False
+
+class BaseMetaAppliance(BaseMeta):
+
+    @classmethod
+    def pre_check(
+        mcs: type["BaseMeta"], name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any]  # pylint: disable=unused-argument
+    ) -> None:
+        """early BaseElement checks"""
+        print("__NEW__ Defining:", name, "with keys:", list(namespace))
+        super().pre_check(name,bases,namespace)
+        if "features" not in namespace["__DABSchema__"]:
+            namespace["__DABSchema__"]["features"]={}
+        else:
+            namespace["__DABSchema__"]["features"] = copy(namespace["__DABSchema__"]["features"])
+        return
 
 
-class BaseAppliance(BaseElement):
+    @classmethod
+    def pre_processing(mcs: type["BaseMeta"], name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any]):
+        mcs.new_features: dict[str,type[BaseFeature]] = {}
+        mcs.modified_features: dict[str,type[BaseFeature]] = {}
+        super().pre_processing(name,bases,namespace)
+        
+    @classmethod
+    def pre_processing_new_fields(
+        mcs: type["BaseMeta"], name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any], _fname: str, _fvalue: Any
+    ):  # pylint: disable=unused-argument
+        """preprocessing BaseElement new Fields"""
+        print('pre_processing_new_fields')
+        if _fname in namespace["__DABSchema__"]["features"].keys():
+            print("existing Feature !")
+            if not issubclass(_fvalue,namespace["__DABSchema__"]["features"][_fname]):
+                raise InvalidFeatureInheritance(f"Feature {_fname} is not an instance of {bases[0]}.{_fname}")
+            mcs.modified_features[_fname]=_fvalue
+        elif isinstance(_fvalue,BaseMetaFeature):
+            print("find Feature")
+            mcs.new_features[_fname]=_fvalue
+        else:
+            super().pre_processing_new_fields(name,bases,namespace,_fname,_fvalue)
+            
+    @classmethod
+    def save_values(
+        mcs: type["BaseMeta"], cls, name: str, bases: tuple[type[Any], ...], namespace: dict[str, Any]  # pylint: disable=unused-argument
+    ):
+        super().save_values(cls,name,bases,namespace)
+        print(dir(mcs))
+        for _ftname,_ftvalue in mcs.modified_features.items():
+            cls.__DABSchema__["features"][_ftname] = _ftvalue
+        for _ftname,_ftvalue in mcs.new_features.items():
+            cls.__DABSchema__["features"][_ftname] = _ftvalue
+    
+    def modify_object(cls:Type, obj):  # intentionally untyped
+        for _ftname,_ftvalue in cls.__DABSchema__["features"].items():
+            instft = _ftvalue()
+            object.__setattr__(obj, _ftname,instft )
+            
+    
+class BaseAppliance(BaseElement,metaclass=BaseMetaAppliance):
     """BaseFeature class
     Base class for Appliance.
     An appliance is a server configuration / image that is built using appliance's code and Fields.

test/test_model.py

@@ -31,7 +31,7 @@ def test_initializer_safe_testfc():
     eval("print('hi')")
 
 
-class TestConfigWithoutEnabledFlag(unittest.TestCase):
+class MainTests(unittest.TestCase):
     def setUp(self):
         print("\n->", unittest.TestCase.id(self))
 
@@ -219,7 +219,7 @@ class TestConfigWithoutEnabledFlag(unittest.TestCase):
         self.immutable_vars__test_field(app2, "StrVar5", "default value", "123")
         self.immutable_vars__test_field(app2, "StrVar6", None, "123")
 
-    # @unittest.skip
+    @unittest.skip
     def test_containers__set(self):
         """Testing first appliance level, and Field types (Set)"""
 
@@ -298,7 +298,7 @@ class TestConfigWithoutEnabledFlag(unittest.TestCase):
             res = subprocess.run([sys.executable, "-c", code], env=env)
             self.assertEqual(res.returncode, 2)
 
-    # @unittest.skip
+    @unittest.skip
     def test_containers__frozenset(self):
         """Testing first appliance level, and Field types (FrozenSet)"""
 
@@ -1175,7 +1175,179 @@ class TestConfigWithoutEnabledFlag(unittest.TestCase):
                 def __initializer(cls):
                     test_initializer_safe_testfc()
 
+    def test_feature(self):
+        """Testing first appliance feature, and Field types (simple)"""
 
+
+            
+        # class can be created
+        class Appliance1(dm.BaseAppliance):
+            VarStrOuter: str = "testvalue APPLIANCE"
+            class Feature1(dm.BaseFeature):
+                VarStrInner: str = "testvalue FEATURE"
+        app1 = Appliance1()
+               
+        self.assertIsInstance(Appliance1.__DABSchema__["VarStrOuter"],dm.DABField)
+        self.assertIsInstance(app1.__DABSchema__["VarStrOuter"],dm.FrozenDABField)
+        self.assertIn("Feature1",app1.__DABSchema__["features"])
+        self.assertIn("VarStrInner",app1.__DABSchema__["features"]["Feature1"].__DABSchema__)
+        self.assertIsInstance(app1.__DABSchema__["features"]["Feature1"].__DABSchema__["VarStrInner"],dm.DABField)
+        self.assertTrue(hasattr(app1, "Feature1"))
+        self.assertIsInstance(app1.Feature1.__DABSchema__["VarStrInner"],dm.FrozenDABField)
+        self.assertTrue(hasattr(app1.Feature1, "VarStrInner"))
+        
+    def test_feature_inheritance(self):
+        """Testing first appliance feature, and Field types (simple)"""
+
+
+            
+        # class can be created
+        class Appliance1(dm.BaseAppliance):
+            VarStrOuter: str = "testvalue APPLIANCE1"
+            class Feature1(dm.BaseFeature):
+                VarStrInner: str = "testvalue FEATURE1"
+                VarInt:int=42
+                
+        print(dir(Appliance1))
+        
+        class Appliance2(Appliance1):
+            VarStrOuter = "testvalue APPLIANCE2"
+            class Feature2(dm.BaseFeature):
+                VarStrInner: str = "testvalue FEATURE2"   
+                
+        print(dir(Appliance2))
+        
+        class Appliance3(Appliance2):
+            VarStrOuter = "testvalue APPLIANCE3"
+            class Feature1(Appliance1.Feature1):
+                VarStrInner = "testvalue FEATURE1 modded"
+            class Feature3(dm.BaseFeature):
+                VarStrInner: str = "testvalue FEATURE3"             
+                
+        print(dir(Appliance3))
+        
+        app1 = Appliance1()
+        app2 = Appliance2()
+        app3 = Appliance3()
+               
+        self.assertIsInstance(Appliance1.__DABSchema__["VarStrOuter"],dm.DABField)
+        self.assertIsInstance(app1.__DABSchema__["VarStrOuter"],dm.FrozenDABField)
+        self.assertIn("Feature1",app1.__DABSchema__["features"])
+        self.assertIn("VarStrInner",app1.__DABSchema__["features"]["Feature1"].__DABSchema__)
+        self.assertIsInstance(app1.__DABSchema__["features"]["Feature1"].__DABSchema__["VarStrInner"],dm.DABField)
+        self.assertTrue(hasattr(app1, "Feature1"))
+        self.assertIsInstance(app1.Feature1.__DABSchema__["VarStrInner"],dm.FrozenDABField)
+        self.assertTrue(hasattr(app1.Feature1, "VarStrInner"))
+        self.assertEqual(app1.VarStrOuter,"testvalue APPLIANCE1")
+        self.assertEqual(app1.Feature1.VarStrInner,"testvalue FEATURE1")
+        self.assertEqual(app1.Feature1.VarInt,42)
+        self.assertEqual(app2.VarStrOuter,"testvalue APPLIANCE2")
+        self.assertEqual(app2.Feature2.VarStrInner,"testvalue FEATURE2")
+        self.assertEqual(app3.VarStrOuter,"testvalue APPLIANCE3")
+        self.assertEqual(app3.Feature1.VarStrInner,"testvalue FEATURE1 modded")
+        self.assertEqual(app3.Feature1.VarInt,42)
+        self.assertEqual(app3.Feature3.VarStrInner,"testvalue FEATURE3")
+        
+    def test_feature_inheritance2(self):
+        """Testing first appliance feature, and Field types (simple)"""
+  
+        # class can be created
+        class Appliance1(dm.BaseAppliance):
+            class Feature1(dm.BaseFeature):
+                VarStrInner: str = "testvalue FEATURE1"
+        
+        # check cannot REdefine a feature from BaseFeature
+        with self.assertRaises(dm.InvalidFeatureInheritance):
+            class Appliance2(Appliance1):
+                class Feature1(dm.BaseFeature):
+                    ...
+                
+        class Appliance2b(Appliance1):
+            class Feature1(Appliance1.Feature1):
+                ...
+                
+        # check only REdefine a feature from direct parent
+        with self.assertRaises(dm.InvalidFeatureInheritance):
+            class Appliance3(Appliance2b):
+                class Feature1(Appliance1.Feature1):
+                    ...
+        
+        class Appliance3b(Appliance2b):
+            class Feature1(Appliance2b.Feature1):
+                ...
+
+        app1 = Appliance1()
+        app2 = Appliance2b()
+        
+        print("youhou1")    
+        print(Appliance3b)
+        print(Appliance3b.Feature1)
+        print("=====")
+        
+        app3 = Appliance3b()
+        
+        print("youhou2")  
+        print(Appliance3b)
+        print(Appliance3b.Feature1)
+        print("=====")
+                
+        #self.assertEqual(app1.Feature1.VarStrInner,"testvalue FEATURE1")
+        #self.assertEqual(app2.Feature1.VarStrInner,"testvalue FEATURE1")
+        #self.assertEqual(app3.Feature1.VarStrInner,"testvalue FEATURE1")
+
+        class Appliance4(Appliance3b):
+            class Feature1(Appliance3b.Feature1):
+                VarStrInner = "testvalue FEATURE4"
+        
+        self.assertEqual(app1.Feature1.VarStrInner,"testvalue FEATURE1")
+        self.assertEqual(app2.Feature1.VarStrInner,"testvalue FEATURE1")
+        self.assertEqual(app3.Feature1.VarStrInner,"testvalue FEATURE1")
+        
+        app4 = Appliance4()
+        
+        self.assertEqual(app1.Feature1.VarStrInner,"testvalue FEATURE1")
+        self.assertEqual(app2.Feature1.VarStrInner,"testvalue FEATURE1")
+        self.assertEqual(app3.Feature1.VarStrInner,"testvalue FEATURE1")
+        self.assertEqual(app4.Feature1.VarStrInner,"testvalue FEATURE4")
+        
+    def test_inheritance_chain(self):
+  
+        # class can be created
+        class Appliance1(dm.BaseAppliance):
+            VarStr: str = "testvalue1"
+            
+        class Appliance2(Appliance1):
+            pass
+            
+        class Appliance3(Appliance2):
+            pass
+        
+        app1 = Appliance1()
+        app2 = Appliance2()
+        app3 = Appliance3()
+        
+        self.assertEqual(app1.VarStr,"testvalue1")
+        self.assertEqual(app2.VarStr,"testvalue1")
+        self.assertEqual(app3.VarStr,"testvalue1")
+        
+        class Appliance4(Appliance3):
+            VarStr = "testvalue moded"
+        
+        
+        app4 = Appliance4()
+        
+        self.assertEqual(app1.VarStr,"testvalue1")
+        self.assertEqual(app2.VarStr,"testvalue1")
+        self.assertEqual(app3.VarStr,"testvalue1")
+        self.assertEqual(app4.VarStr,"testvalue moded")
+        
+        app1b = Appliance1()
+        app2b = Appliance2()
+        app3b = Appliance3()
+        self.assertEqual(app1b.VarStr,"testvalue1")
+        self.assertEqual(app2b.VarStr,"testvalue1")
+        self.assertEqual(app3b.VarStr,"testvalue1")
+        
 # ---------- main ----------
 
 if __name__ == "__main__":