Merge pull request #6 from yezyilomo/add_shortcircuiting

Add shortcircuiting

drf_guard/__init__.py

@@ -1,7 +1,7 @@
 __title__ = 'DRF Guard'
 __description__ = 'Flexible permissions for Django REST Framework'
 __url__ = 'https://github.com/yezyilomo/drf-guard'
-__version__ = '0.1.0'
+__version__ = '0.1.1'
 __author__ = 'Yezy Ilomo'
 __author_email__ = 'yezileliilomo@hotmail.com'
 __license__ = 'MIT'

drf_guard/operators.py

@@ -3,23 +3,37 @@
 
 class Operator():
     @property
-    def has_operands(self):
+    def should_eval(self):
         return hasattr(self, 'left_operand') and hasattr(self, 'right_operand')
 
 
 class Or(Operator):
+    @property
+    def should_eval(self):
+        if getattr(self, 'left_operand', False):
+            # Shortcircuit
+            raise StopIteration(self.left_operand)
+        return super().should_eval
+
     def eval(self):
         return self.left_operand or self.right_operand
 
 
 class And(Operator):
+    @property
+    def should_eval(self):
+        if not getattr(self, 'left_operand', True):
+            # Shortcircuit
+            raise StopIteration(self.left_operand)
+        return super().should_eval
+
     def eval(self):
         return self.left_operand and self.right_operand
 
 
 class Not(Operator):
     @property
-    def has_operands(self):
+    def should_eval(self):
         return hasattr(self, 'right_operand')
 
     def eval(self):
@@ -47,18 +61,22 @@ def reducer(self, left_operand, right_operand):
 
         if isinstance(left_operand, Operator):
             left_operand.right_operand = right_operand
-            if left_operand.has_operands:
+            if left_operand.should_eval:
                 return left_operand.eval()
             return left_operand
 
         if isinstance(right_operand, Operator):
             right_operand.left_operand = left_operand
-            if right_operand.has_operands:
+            if right_operand.should_eval:
                 return right_operand.eval()
             return right_operand
 
         return left_operand and right_operand # Default operator for ','
 
     def eval(self, sequence):
-        return reduce(self.reducer, sequence)
+        try:
+            return reduce(self.reducer, sequence)
+        except StopIteration as e:
+            # Return value due to shortcircuit
+            return e.args[0]
 

drf_guard/permissions.py

@@ -75,18 +75,6 @@ class HasRequiredPermissions(permissions.BasePermission):
     """
     Ensure user is has required permissions.
     """
-    @classmethod
-    def has_required_permissions(cls, permissions, *args):
-        if permissions is None:
-            # Don't check the permissions
-            return True
-
-        reducer = Reducer()
-        return reducer([
-            cls.has_required_permission(permission, *args)
-            for permission in permissions
-        ])
-
     @classmethod
     def has_required_permission(cls, permission, request, view, obj=None):
         if isinstance(permission, str):
@@ -107,6 +95,18 @@ def has_required_permission(cls, permission, request, view, obj=None):
             data_type = type(permission).__name__
             raise TypeError("`%s` is invalid permission type." % data_type)
 
+    @classmethod
+    def has_required_permissions(cls, permissions, *args):
+        if permissions is None:
+            # Don't check the permissions
+            return True
+
+        reducer = Reducer()
+        return reducer([
+            cls.has_required_permission(permission, *args)
+            for permission in permissions
+        ])
+
     @staticmethod
     def get_permissions(request, view):
         # Get a mapping of methods -> required group.