From 119dff7a067272d7a73c9cbff96b2f168a859d43 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20T=C3=B6rnqvist?= <mjt+illyria@skyhood.com>
Date: Sun, 19 May 2013 18:01:12 +0300
Subject: [PATCH 1/4] Introduce validator metaclass

---
 rest_framework/class_validator.py | 41 +++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 rest_framework/class_validator.py

diff --git a/rest_framework/class_validator.py b/rest_framework/class_validator.py
new file mode 100644
index 000000000..68d3d9ba3
--- /dev/null
+++ b/rest_framework/class_validator.py
@@ -0,0 +1,41 @@
+"""Attribute checking for Python classes
+"""
+
+class InvalidAttributeError(AttributeError):
+    """
+    Use this for invalid attributes because AttributeError means not found
+    """
+
+    pass
+
+
+class ValidatorMeta(type):
+    """
+    Metaclass to guard against setting unrecognized attributes
+    Set it as __metaclass__ as low in the inheritance chain as possible
+    """
+    def __new__(cls, name, parents, kwargs):
+        """Creates the new class, and sees if it has only known attributes
+        """
+        new_cls = type.__new__(cls, name, parents, kwargs)
+
+        ## Fail only if the new class defines an api
+        if not new_cls.__dict__.has_key('valid_attributes'):
+            return new_cls
+
+        ## Do some sanity checks to not fail in vain
+        for attr, val in kwargs.items():
+            if attr == 'valid_attributes':
+                continue
+            if attr.startswith('_'):
+                continue
+            # Methods are always allowed
+            if callable(val):
+                continue
+
+            # Ensure validity
+            if not attr in new_cls.valid_attributes:
+                raise InvalidAttributeError(attr)
+
+        return new_cls
+

From c2a17ab6a3eb2e1221dd7804e3b7297667bba984 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20T=C3=B6rnqvist?= <mjt+illyria@skyhood.com>
Date: Sun, 19 May 2013 18:03:27 +0300
Subject: [PATCH 2/4] Conceptual design for strong attributes in APIView

---
 rest_framework/views.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/rest_framework/views.py b/rest_framework/views.py
index 555fa2f40..7d19847bc 100644
--- a/rest_framework/views.py
+++ b/rest_framework/views.py
@@ -14,6 +14,14 @@ from rest_framework.utils.formatting import get_view_name, get_view_description
 
 
 class APIView(View):
+    __metaclass__ = ValidatorMeta
+    valid_attributes = set(('settings', 'renderer_classes', 'parser_classes',
+        'authentication_classes', 'throttle_classes',
+        'permission_classes', 'content_negotiation_class',
+        'allowed_methods', 'default_response_headers',
+        'as_view',
+    ))
+
     settings = api_settings
 
     renderer_classes = api_settings.DEFAULT_RENDERER_CLASSES

From 5314927b6b12e9dcfb1c09f18392f44b8b98e365 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20T=C3=B6rnqvist?= <mjt+illyria@skyhood.com>
Date: Sun, 19 May 2013 18:04:17 +0300
Subject: [PATCH 3/4] Demonstration (in code, look at the diff) of attribute
 validation

---
 rest_framework/tests/views.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/rest_framework/tests/views.py b/rest_framework/tests/views.py
index 994cf6dc3..eb0a78f65 100644
--- a/rest_framework/tests/views.py
+++ b/rest_framework/tests/views.py
@@ -12,6 +12,10 @@ factory = RequestFactory()
 
 
 class BasicView(APIView):
+    ## Uncomment this to see how attribute validation works
+    # valid_attributes = ('foo', )
+    # foo = 'foo'
+    # bar = 'bar'
     def get(self, request, *args, **kwargs):
         return Response({'method': 'GET'})
 

From 365ad2f6007ca1b9fb5a617ee2dd3d0f219c1f48 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20T=C3=B6rnqvist?= <mjt+illyria@skyhood.com>
Date: Sun, 19 May 2013 18:15:58 +0300
Subject: [PATCH 4/4] Oops! Forgot the import from the push

---
 rest_framework/views.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/rest_framework/views.py b/rest_framework/views.py
index 7d19847bc..343292e97 100644
--- a/rest_framework/views.py
+++ b/rest_framework/views.py
@@ -10,6 +10,7 @@ from rest_framework.compat import View
 from rest_framework.response import Response
 from rest_framework.request import Request
 from rest_framework.settings import api_settings
+from rest_framework.class_validator import ValidatorMeta
 from rest_framework.utils.formatting import get_view_name, get_view_description