add Magic mixins

docs/source/magic.rst

@@ -3,4 +3,6 @@ Pankoff's magic
 
 .. autofunction:: pankoff.magic.autoinit(klass, verbose=False)
 
-.. autoclass:: pankoff.magic.Alias
+.. autoclass:: pankoff.magic.Alias
+
+.. autoclass:: pankoff.magic.MagicMixin

docs/source/usage.rst

@@ -183,3 +183,64 @@ It is possible to make object factory based on the same Container class.
 As you can see, ``young_person`` and ``old_person`` acting like completely different things, but in fact they're not.
 
 Also, you can access underlying ``extra`` structure by doing ``yaroslav._extra``, which returns ``MappingProxyType`` view.
+
+.. _Magic mixins:
+
+Magic mixins
+------------
+
+Lets say you want to create a mixin, normally you'd do:
+
+.. code-block:: python
+
+    class HelloMixin:
+
+        def say(self):
+            value = super().say()
+            return f"My name is {value} !!!"
+
+
+    class Hello:
+
+        def say(self):
+            return self.name
+
+
+    class Person(HelloMixin, Hello):
+        def __init__(self, name):
+            self.name = name
+
+    person = Person("Yaroslav")
+    print(person.say())  # hello, my name is Yaroslav
+
+As you can see, we're using ``super()`` here. Magic mixins allows you to avoid that, e.g:
+
+.. code-block:: python
+
+    from pankoff.magic import MagicMixin
+
+    class HelloMixin(MagicMixin):
+
+        def say(self, value):
+            return f"My name is {value} !!!"
+
+
+    class Hello:
+
+        def say(self):
+            return self.name
+
+
+    class Person(HelloMixin, Hello):
+        def __init__(self, name):
+            self.name = name
+
+
+    person = Person("Yaroslav")
+    print(person.say())  # hello, my name is Yaroslav
+
+So the idea is, when you have same method names in both mixin and its parent, mixin will consume parents' value implicitly.
+
+In the example above, ``value`` parameter for ``HelloMixin`` is the result ``say`` method on ``Hello`` class.
+
+Note that it'll chain through all the mixins in MRO.

pankoff/magic.py

@@ -1,3 +1,6 @@
+import inspect
+import textwrap
+
 from pankoff.base import BaseValidator
 from pankoff.validators import UNSET, LazyLoad
 
@@ -103,6 +106,48 @@ def inner(cls):
     return inner
 
 
+def _replace_method(method):
+    ns = {
+        "UNSET": UNSET,
+        "method": method
+    }
+    mixin_method_template = textwrap.dedent("""
+    def mixed_method_{method_name}(self, *args, **kwargs):
+        parent = eval(f"getattr(super(klass, self), '{method_name}', UNSET)")
+        if parent is UNSET:
+            return method(self, *args, **kwargs)
+        else:
+            return method(self, parent(*args, **kwargs))
+    """)
+    exec(mixin_method_template.format(method_name=method.__name__), ns)
+    return ns[f"mixed_method_{method.__name__}"], ns
+
+
+class MixinMeta(type):
+
+    def __new__(mcs, name, bases, namespace):
+        nss = []
+        if all(issubclass(base, MagicMixin) for base in bases):
+            for k, v in namespace.items():
+                if inspect.isfunction(v) or isinstance(v, classmethod):
+                    new_f, ns = _replace_method(v)
+                    namespace[k] = new_f
+                    nss.append(ns)
+        klass = super().__new__(mcs, name, bases, namespace)
+        for ns in nss:
+            ns["klass"] = klass
+        return klass
+
+
+class MagicMixin(metaclass=MixinMeta):
+    """
+    Create ``MagicMixin`` by inheriting from it.
+
+    See examples: :ref:`magic mixins`
+    """
+    pass
+
+
 class Alias:
     """
     Create and alias for your fields.

setup.py

@@ -3,7 +3,7 @@
 """
 from distutils.core import setup
 
-version = "15.5"
+version = "15.6"
 setup(
     name='pankoff',
     packages=['pankoff'],