Preserve permission messages.

.gitignore

@@ -41,3 +41,5 @@ venv/
 
 # Some temp files
 .DS_Store
+
+.idea/

Pipfile

@@ -0,0 +1,12 @@
+[[source]]
+url = "https://pypi.org/simple"
+verify_ssl = true
+name = "pypi"
+
+[packages]
+djangorestframework = "==3.8.*"
+
+[dev-packages]
+
+[requires]
+python_version = "*"

rest_condition/permissions.py

@@ -15,7 +15,7 @@ def _is_permission_factory(obj):
 
 
 class ConditionalPermission(permissions.BasePermission):
-    '''
+    """
     Example of usage:
     >>> class MyView(GinericView):
     >>>     permission_classes = (ConditionalPermission, )
@@ -24,7 +24,7 @@ class ConditionalPermission(permissions.BasePermission):
     Or you can just:
     >>> class MyView(GinericView):
     >>>     permission_classes = (C(Perm1) | ~C(Perm2), )
-    '''
+    """
     permission_condition_field = 'permission_condition'
 
     def get_permission_condition(self, view):
@@ -47,7 +47,7 @@ def has_permission(self, request, view):
 
 
 class Condition(object):
-    '''
+    """
     Provides a simple way to define complex and multi-depth
     (with logic operators) permissions tree.
 
@@ -61,7 +61,7 @@ class Condition(object):
     permission will be evaluated to `True`:
     >>> cond1 = C(Perm1, Perm2, Perm3, Perm4,
     >>>           reduce_op=operator.add, lazy_until=3, negated=True)
-    '''
+    """
     @classmethod
     def And(cls, *perms_or_conds):
         return cls(reduce_op=operator.and_, lazy_until=False, *perms_or_conds)
@@ -79,13 +79,17 @@ def __init__(self, *perms_or_conds, **kwargs):
         self.reduce_op = kwargs.get('reduce_op', operator.and_)
         self.lazy_until = kwargs.get('lazy_until', False)
         self.negated = kwargs.get('negated')
+        self.message = None
 
     def evaluate_permissions(self, permission_name, *args, **kwargs):
+
         reduced_result = _NONE
+        last_condition = None
 
         for condition in self.perms_or_conds:
             if hasattr(condition, 'evaluate_permissions'):
-                result = condition.evaluate_permissions(permission_name, *args, **kwargs)
+                result = condition.evaluate_permissions(
+                    permission_name, *args, **kwargs)
             else:
                 if _is_permission_factory(condition):
                     condition = condition()
@@ -103,9 +107,16 @@ def evaluate_permissions(self, permission_name, *args, **kwargs):
             else:
                 reduced_result = self.reduce_op(reduced_result, result)
 
-            if self.lazy_until is not None and self.lazy_until is reduced_result:
+            last_condition = condition
+
+            if self.lazy_until is not None and \
+                    self.lazy_until is reduced_result:
                 break
 
+        message = getattr(last_condition, 'message', None)
+        if message:
+            self.message = message
+
         if reduced_result is not _NONE:
             return not reduced_result if self.negated else reduced_result
 

tests/tests/test_permissions.py

@@ -23,15 +23,34 @@ def test_permission(self, request):
 
         return True
 
+    def test_message(self, request):
+        from rest_framework.request import Request
+
+        request = Request(request)
+
+        self.request = request
+
+        last_permission = None
+
+        for permission in self.get_permissions():
+            last_permission = permission
+            if not permission.has_permission(request, self):
+                return permission.message
+        return last_permission.message
+
 
 class TruePermission(BasePermission):
 
+    message = "YES"
+
     def has_permission(self, request, view):
         return True
 
 
 class FalsePermission(BasePermission):
 
+    message = "NO"
+
     def has_permission(self, request, view):
         return False
 
@@ -50,7 +69,13 @@ def assertViewPermission(self, view_class, granted=True):
         else:
             self.assertFalse(result)
 
-    def test_conditional_permissions_with_assigment(self):
+    def assertViewPermissionMessage(self, view_class, message):
+        view = view_class()
+        request = self.requests.get('/')
+        permission_message = view.test_message(request)
+        self.assertEqual(message, permission_message)
+
+    def test_conditional_permissions_with_assignment(self):
 
         perm1 = C(TruePermission)
         perm1 |= ~C(TruePermission)
@@ -70,6 +95,32 @@ class View2(TestView):
 
         self.assertViewPermission(View2, True)
 
+    def test_conditional_permissions_with_message(self):
+
+        perm1 = And(TruePermission, FalsePermission)
+
+        class View1(TestView):
+            permission_classes = [perm1]
+
+        self.assertViewPermissionMessage(View1, FalsePermission.message)
+
+        perm2 = Or(TruePermission, FalsePermission)
+
+        class View2(TestView):
+            permission_classes = [perm2]
+
+        self.assertViewPermissionMessage(View2, TruePermission.message)
+
+        perm3 = And(
+            Or(Not(FalsePermission), FalsePermission),
+            Or(Not(TruePermission), FalsePermission)
+        )
+
+        class View3(TestView):
+            permission_classes = [perm3]
+
+        self.assertViewPermissionMessage(View3, FalsePermission.message)
+
     def test_single_conditional_permission_true(self):
 
         class View1(TestView):

tests/urls.py

@@ -1,9 +1,15 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
+from rest_framework.views import APIView
 try:
-    from django.conf.urls import include, patterns, url
+    from django.conf.urls import patterns
 except ImportError:
-    from django.conf.urls.defaults import include, patterns, url
+    try:
+        from django.conf.urls.defaults import patterns
+    except ImportError:
+        from django.urls import path
+        patterns = lambda x: [path('', APIView.as_view())]
+
 
 urlpatterns = patterns('', )