Decouple viewset mixins from models

Author: sergioisidoro

rules/contrib/rest_framework.py

@@ -1,6 +1,8 @@
 from django.core.exceptions import ImproperlyConfigured, PermissionDenied
+
 from ..viewsets import BaseAutoPermissionMixin
 
+
 class AutoPermissionViewSetMixin(BaseAutoPermissionMixin):
     """
     Enforces object-level permissions in ``rest_framework.viewsets.ViewSet``,

rules/viewsets.py

@@ -1,5 +1,21 @@
 # All auto permission mixins (both for DRF and Django views)
 # inherit from this mixin.
 class BaseAutoPermissionMixin:
+    def get_perm(self, model, perm_type):
+        return "%s.%s_%s" % (model._meta.app_label, perm_type, model._meta.model_name)
+
     def get_permission_for_model(self, model, perm_type):
-        return model.get_perm(perm_type)
+
+        # Attempt to use model mixin. If model mixin is not available,
+        # default to standard convetion of this project (or allow
+        # overriding `get_perm` through a custom Mixin)
+        try:
+            use_model_mixin_method = callable(model.get_perm)
+        except AttributeError:
+            use_model_mixin_method = False
+
+        if use_model_mixin_method:
+            perm = model.get_perm(perm_type)
+        else:
+            perm = self.get_perm(model, perm_type)
+        return perm