Fixed #15012 -- Added post-rendering callbacks to TemplateResponse so that decorators (in particular, the cache decorator) can defer processing until after rendering has occurred. Thanks to Joshua Ginsberg for the draft patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15295 bcc190cf-cafb-0310-a4f2-bffc1f526a37

2 files changed, 54 insertions, 2 deletions

diff --git a/django/middleware/cache.py b/django/middleware/cache.py
index 907edbb16f..ab72db3c18 100644
--- a/django/middleware/cache.py
+++ b/django/middleware/cache.py
@@ -52,6 +52,7 @@ from django.conf import settings
 from django.core.cache import get_cache, DEFAULT_CACHE_ALIAS
 from django.utils.cache import get_cache_key, learn_cache_key, patch_response_headers, get_max_age
 
+
 class UpdateCacheMiddleware(object):
     """
     Response-phase cache middleware that updates the cache if the response is
@@ -87,7 +88,12 @@ class UpdateCacheMiddleware(object):
         patch_response_headers(response, timeout)
         if timeout:
             cache_key = learn_cache_key(request, response, timeout, self.key_prefix, cache=self.cache)
-            self.cache.set(cache_key, response, timeout)
+            if hasattr(response, 'render') and callable(response.render):
+                response.add_post_render_callback(
+                    lambda r: self.cache.set(cache_key, r, timeout)
+                )
+            else:
+                self.cache.set(cache_key, response, timeout)
         return response
 
 class FetchFromCacheMiddleware(object):
diff --git a/django/template/response.py b/django/template/response.py
index 629461aa5e..a6ef893520 100644
--- a/django/template/response.py
+++ b/django/template/response.py
@@ -19,12 +19,30 @@ class SimpleTemplateResponse(HttpResponse):
         # a final response.
         self._is_rendered = False
 
+        self._post_render_callbacks = []
+
         # content argument doesn't make sense here because it will be replaced
         # with rendered template so we always pass empty string in order to
         # prevent errors and provide shorter signature.
         super(SimpleTemplateResponse, self).__init__('', mimetype, status,
                                                      content_type)
 
+    def __getstate__(self):
+        """Pickling support function.
+
+        Ensures that the object can't be pickled before it has been
+        rendered, and that the pickled state only includes rendered
+        data, not the data used to construct the response.
+        """
+        obj_dict = self.__dict__.copy()
+        if not self._is_rendered:
+            raise ContentNotRenderedError('The response content must be rendered before it can be pickled.')
+        del obj_dict['template_name']
+        del obj_dict['context_data']
+        del obj_dict['_post_render_callbacks']
+
+        return obj_dict
+
     def resolve_template(self, template):
         "Accepts a template object, path-to-template or list of paths"
         if isinstance(template, (list, tuple)):
@@ -57,6 +75,16 @@ class SimpleTemplateResponse(HttpResponse):
         content = template.render(context)
         return content
 
+    def add_post_render_callback(self, callback):
+        """Add a new post-rendering callback.
+
+        If the response has already been rendered, invoke the callback immediately.
+        """
+        if self._is_rendered:
+            callback(self)
+        else:
+            self._post_render_callbacks.append(callback)
+
     def render(self):
         """Render (thereby finalizing) the content of the response.
 
@@ -66,6 +94,8 @@ class SimpleTemplateResponse(HttpResponse):
         """
         if not self._is_rendered:
             self._set_content(self.rendered_content)
+            for post_callback in self._post_render_callbacks:
+                post_callback(self)
         return self
 
     is_rendered = property(lambda self: self._is_rendered)
@@ -81,7 +111,7 @@ class SimpleTemplateResponse(HttpResponse):
         return super(SimpleTemplateResponse, self)._get_content()
 
     def _set_content(self, value):
-        "Overrides rendered content, unless you later call render()"
+        "Sets the content for the response"
         super(SimpleTemplateResponse, self)._set_content(value)
         self._is_rendered = True
 
@@ -101,6 +131,20 @@ class TemplateResponse(SimpleTemplateResponse):
         super(TemplateResponse, self).__init__(
             template, context, mimetype, status, content_type)
 
+    def __getstate__(self):
+        """Pickling support function.
+
+        Ensures that the object can't be pickled before it has been
+        rendered, and that the pickled state only includes rendered
+        data, not the data used to construct the response.
+        """
+        obj_dict = super(TemplateResponse, self).__getstate__()
+
+        del obj_dict['_request']
+        del obj_dict['_current_app']
+
+        return obj_dict
+
     def resolve_context(self, context):
         """Convert context data into a full RequestContext object
         (assuming it isn't already a Context object).
@@ -109,3 +153,5 @@ class TemplateResponse(SimpleTemplateResponse):
             return context
         else:
             return RequestContext(self._request, context, current_app=self._current_app)
+
+