Ticket #4148: 5078-fix_ie_vary_bug_core__for_4148.diff

conf/global_settings.py

@@ -240 +240 @@
 # isExistingURL validator.
 URL_VALIDATOR_USER_AGENT = "Django/0.96pre (http://www.djangoproject.com)"
 
+# A boolean that determines whether or not the response will have the Vary
+# header removed to work with Internet Explorer in some cases.
+ENABLE_IE_VARY_FIX = True
+
 ##############
 # MIDDLEWARE #
 ##############

core/handlers/base.py

@@ -3 +3 @@
 from django import http
 import sys
 
+def fix_IE_for_vary(request, response):
+    """
+    This function will fix the bug reported at
+    http://support.microsoft.com/kb/824847/en-us?spid=8722&sid=global
+    by clearing the Vary header whenever the mime-type is not safe
+    enough for Internet Explorer to handle.
+    """
+    
+    # a list of mime-types that are decreed "Vary-safe" for IE
+    safe_mime_types = ('text/html',
+                       'text/plain',
+                       'text/sgml',
+                       )
+
+    # establish that the user is using IE
+    try:
+        if 'MSIE' not in request.META['User-Agent'].upper():
+            return response
+    except KeyError:
+        return response
+
+
+    # IE will break
+    if response.mimetype.lower() not in safe_mime_types: 
+        try:
+            del response['Vary']
+            response['Pragma'] = 'no-cache'
+            response['Cache-Control'] = 'no-cache, must-revalidate'
+        except KeyError:
+            return response
+            
+    return response
+
 class BaseHandler(object):
     def __init__(self):
         self._request_middleware = self._view_middleware = self._response_middleware = self._exception_middleware = None
@@ -17 +50 @@
         from django.core import exceptions
         self._request_middleware = []
         self._view_middleware = []
-        self._response_middleware = []
+        if settings.ENABLE_IE_VARY_FIX:
+            self._response_middleware = [fix_IE_for_vary]
+        else:
+            self._response_middleware = []
+            
         self._exception_middleware = []
         for middleware_path in settings.MIDDLEWARE_CLASSES:
             try:
@@ -45 +82 @@
                 self._view_middleware.append(mw_instance.process_view)
             if hasattr(mw_instance, 'process_response'):
                 self._response_middleware.insert(0, mw_instance.process_response)
+            
             if hasattr(mw_instance, 'process_exception'):
                 self._exception_middleware.insert(0, mw_instance.process_exception)
+                
 
     def get_response(self, request):
         "Returns an HttpResponse object for the given HttpRequest"