Fixed #5898 -- Changed a few response processing paths to make things harder to get wrong and easier to get right. Previous behaviour wasn't buggy, but it was harder to use than necessary.

We now have automatic HEAD processing always (previously required ConditionalGetMiddleware), middleware benefits from the Location header rewrite, so they can use relative URLs as well, and responses with response codes 1xx, 204 or 304 will always have their content removed, in accordance with the HTTP spec (so it's much harder to indavertently deliver invalid responses).

Based on a patch and diagnosis from regexbot@gmail.com.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@6662 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/handlers/base.py

@@ -4,6 +4,10 @@ from django import http
 import sys
 
 class BaseHandler(object):
+    # Changes that are always applied to a response (in this order).
+    response_fixes = [http.fix_location_header,
+            http.conditional_content_removal]
+
     def __init__(self):
         self._request_middleware = self._view_middleware = self._response_middleware = self._exception_middleware = None
 
@@ -50,10 +54,6 @@ class BaseHandler(object):
 
     def get_response(self, request):
         "Returns an HttpResponse object for the given HttpRequest"
-        response = self._real_get_response(request)
-        return fix_location_header(request, response)
-
-    def _real_get_response(self, request):
         from django.core import exceptions, urlresolvers
         from django.core.mail import mail_admins
         from django.conf import settings
@@ -134,15 +134,13 @@ class BaseHandler(object):
         import traceback
         return '\n'.join(traceback.format_exception(*(exc_info or sys.exc_info())))
 
-def fix_location_header(request, response):
+    def apply_response_fixes(self, request, response):
         """
-    Ensure that we always use an absolute URI in any location header in the
-    response. This is required by RFC 2616, section 14.30.
-
-    Code constructing response objects is free to insert relative paths and
-    this function converts them to absolute paths.
+        Applies each of the functions in self.response_fixes to the request and
+        response, modifying the response in the process. Returns the new
+        response.
         """
-    if 'Location' in response and request.get_host():
-        response['Location'] = request.build_absolute_uri(response['Location'])
+        for func in self.response_fixes:
+            response = func(request, response)
         return response
 

django/core/handlers/modpython.py

@@ -162,6 +162,7 @@ class ModPythonHandler(BaseHandler):
                 # Apply response middleware
                 for middleware_method in self._response_middleware:
                     response = middleware_method(request, response)
+                response = self.apply_response_fixes(request, response)
         finally:
             dispatcher.send(signal=signals.request_finished)
 

django/core/handlers/wsgi.py

@@ -207,6 +207,7 @@ class WSGIHandler(BaseHandler):
                 # Apply response middleware
                 for middleware_method in self._response_middleware:
                     response = middleware_method(request, response)
+                response = self.apply_response_fixes(request, response)
         finally:
             dispatcher.send(signal=signals.request_finished)
 
@@ -220,3 +221,4 @@ class WSGIHandler(BaseHandler):
             response_headers.append(('Set-Cookie', str(c.output(header=''))))
         start_response(status, response_headers)
         return response
+

django/http/__init__.py

@@ -5,6 +5,7 @@ from urllib import urlencode
 from urlparse import urljoin
 from django.utils.datastructures import MultiValueDict, FileDict
 from django.utils.encoding import smart_str, iri_to_uri, force_unicode
+from utils import *
 
 RESERVED_CHARS="!*'();:@&=+$,/?%#[]"
 

django/http/utils.py

@@ -0,0 +1,34 @@
+"""
+Functions that modify an HTTP request or response in some way.
+"""
+
+# This group of functions are run as part of the response handling, after
+# everything else, including all response middleware. Think of them as
+# "compulsory response middleware". Be careful about what goes here, because
+# it's a little fiddly to override this behaviour, so they should be truly
+# universally applicable.
+
+def fix_location_header(request, response):
+    """
+    Ensures that we always use an absolute URI in any location header in the
+    response. This is required by RFC 2616, section 14.30.
+
+    Code constructing response objects is free to insert relative paths and
+    this function converts them to absolute paths.
+    """
+    if 'Location' in response and request.get_host():
+        response['Location'] = request.build_absolute_uri(response['Location'])
+    return response
+
+def conditional_content_removal(request, response):
+    """
+    Removes the content of responses for HEAD requests, 1xx, 204 and 304
+    responses. Ensures compliance with RFC 2616, section 4.3.
+    """
+    if 100 <= response.status_code < 200 or response.status_code in (204, 304):
+       response.content = ''
+       response['Content-Length'] = 0
+    if request.method == 'HEAD':
+        response.content = ''
+    return response
+

django/middleware/http.py

@@ -6,8 +6,6 @@ class ConditionalGetMiddleware(object):
     Last-Modified header, and the request has If-None-Match or
     If-Modified-Since, the response is replaced by an HttpNotModified.
 
-    Removes the content from any response to a HEAD request.
-
     Also sets the Date and Content-Length response-headers.
     """
     def process_response(self, request, response):
@@ -18,19 +16,17 @@ class ConditionalGetMiddleware(object):
         if response.has_header('ETag'):
             if_none_match = request.META.get('HTTP_IF_NONE_MATCH', None)
             if if_none_match == response['ETag']:
-                response.status_code = 304
-                response.content = ''
-                response['Content-Length'] = '0'
+                # Setting the status is enough here. The response handling path
+                # automatically removes content for this status code (in
+                # http.conditional_content_removal()).
+                response.status = 304
 
         if response.has_header('Last-Modified'):
             if_modified_since = request.META.get('HTTP_IF_MODIFIED_SINCE', None)
             if if_modified_since == response['Last-Modified']:
-                response.status_code = 304
-                response.content = ''
-                response['Content-Length'] = '0'
-
-        if request.method == 'HEAD':
-            response.content = ''
+                # Setting the status code is enough here (same reasons as
+                # above).
+                response.status = 304
 
         return response
 

django/test/client.py

@@ -42,7 +42,7 @@ class ClientHandler(BaseHandler):
             # Apply response middleware
             for middleware_method in self._response_middleware:
                 response = middleware_method(request, response)
-
+            response = self.apply_response_fixes(request, response)
         finally:
             dispatcher.send(signal=signals.request_finished)
 

tests/regressiontests/test_client_regress/models.py

@@ -119,7 +119,7 @@ class AssertRedirectsTests(TestCase):
         try:
             self.assertRedirects(response, '/test_client/get_view/')
         except AssertionError, e:
-            self.assertEquals(str(e), "Response redirected to 'http://testserver/test_client/get_view/?var=value', expected '/test_client/get_view/'")
+            self.assertEquals(str(e), "Response redirected to 'http://testserver/test_client/get_view/?var=value', expected 'http://testserver/test_client/get_view/'")
 
     def test_incorrect_target(self):
         "An assertion is raised if the response redirects to another target"