magic-removal: Added 'never_cache' decorator that sets

'Expires' as a past date and max-age=0, and used it in the 
admin to prevent loss of data in the change_stage view.


git-svn-id: http://code.djangoproject.com/svn/django/branches/magic-removal@2599 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/admin/views/main.py

@@ -2,6 +2,7 @@ from django import forms, template
 from django.conf import settings
 from django.contrib.admin.filterspecs import FilterSpec
 from django.contrib.admin.views.decorators import staff_member_required
+from django.views.decorators.cache import never_cache
 from django.contrib.contenttypes.models import ContentType
 from django.core.exceptions import ImproperlyConfigured, ObjectDoesNotExist, PermissionDenied
 from django.core.paginator import ObjectPaginator, InvalidPage
@@ -394,7 +395,7 @@ def change_stage(request, app_label, model_name, object_id):
         'is_popup': request.REQUEST.has_key('_popup'),
     })
     return render_change_form(model, manipulator, c, change=True)
-change_stage = staff_member_required(change_stage)
+change_stage = staff_member_required(never_cache(change_stage))
 
 def _nest_help(obj, depth, val):
     current = obj
@@ -515,7 +516,7 @@ def delete_stage(request, app_label, model_name, object_id):
     return render_to_response(["admin/%s/%s/delete_confirmation" % (app_label, opts.object_name.lower() ),
                                "admin/%s/delete_confirmation" % app_label ,
                                "admin/delete_confirmation"], extra_context, context_instance=template.RequestContext(request))
-delete_stage = staff_member_required(delete_stage)
+delete_stage = staff_member_required(never_cache(delete_stage))
 
 def history(request, app_label, model_name, object_id):
     model = models.get_model(app_label, model_name)

django/utils/cache.py

@@ -80,6 +80,8 @@ def patch_response_headers(response, cache_timeout=None):
     if not response.has_header('Expires'):
         expires = now + datetime.timedelta(0, cache_timeout)
         response['Expires'] = expires.strftime('%a, %d %b %Y %H:%M:%S GMT')
+    if cache_timeout < 0:
+        cache_timeout = 0 # Can't have max-age negative
     patch_cache_control(response, max_age=cache_timeout)
 
 def patch_vary_headers(response, newheaders):

django/views/decorators/cache.py

@@ -13,8 +13,9 @@ account on caching -- just like the middleware does.
 import re
 
 from django.utils.decorators import decorator_from_middleware
-from django.utils.cache import patch_cache_control
+from django.utils.cache import patch_cache_control, patch_response_headers
 from django.middleware.cache import CacheMiddleware
+import datetime
 
 cache_page = decorator_from_middleware(CacheMiddleware)
 
@@ -31,3 +32,14 @@ def cache_control(**kwargs):
 
     return _cache_controller
 
+
+def never_cache(view_func):
+    """
+    Decorator that adds headers to a response so that it will
+    never be cached.
+    """
+    def _wrapped_view_func(request, *args, **kwargs):
+        response = view_func(request, *args, **kwargs)
+        patch_response_headers(response, cache_timeout=-1)
+        return response
+    return _wrapped_view_func