From a2e26150b77cd2cdad4cc9de120a87a6370c6dd5 Mon Sep 17 00:00:00 2001
From: Adrian Holovaty <adrian@holovaty.com>
Date: Sat, 15 Oct 2005 02:20:35 +0000
Subject: [PATCH] Fixed #616 -- Added a process_exception() hook to middleware
 framework. Thanks, Hugo

git-svn-id: http://code.djangoproject.com/svn/django/trunk@880 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 django/core/handlers/base.py | 17 +++++++++++++++--
 django/utils/decorators.py   |  9 ++++++++-
 docs/middleware.txt          | 13 +++++++++++++
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/django/core/handlers/base.py b/django/core/handlers/base.py
index 00149ff791..ecec674d3e 100644
--- a/django/core/handlers/base.py
+++ b/django/core/handlers/base.py
@@ -2,7 +2,7 @@ from django.utils import httpwrappers
 
 class BaseHandler:
     def __init__(self):
-        self._request_middleware = self._view_middleware = self._response_middleware = None
+        self._request_middleware = self._view_middleware = self._response_middleware = self._exception_middleware = None
 
     def load_middleware(self):
         """
@@ -15,6 +15,7 @@ class BaseHandler:
         self._request_middleware = []
         self._view_middleware = []
         self._response_middleware = []
+        self._exception_middleware = []
         for middleware_path in settings.MIDDLEWARE_CLASSES:
             dot = middleware_path.rindex('.')
             mw_module, mw_classname = middleware_path[:dot], middleware_path[dot+1:]
@@ -38,6 +39,8 @@ class BaseHandler:
                 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, path, request):
         "Returns an HttpResponse object for the given HttpRequest"
@@ -61,7 +64,17 @@ class BaseHandler:
                 if response:
                     return response
 
-            response = callback(request, **param_dict)
+            try:
+                response = callback(request, **param_dict)
+            except Exception, e:
+                # If the view raised an exception, run it through exception
+                # middleware, and if the exception middleware returns a
+                # response, use that. Otherwise, reraise the exception.
+                for middleware_method in self._exception_middleware:
+                    response = middleware_method(request, e)
+                    if response:
+                        return response
+                raise e
 
             # Complain if the view returned None (a common error).
             if response is None:
diff --git a/django/utils/decorators.py b/django/utils/decorators.py
index 1333f9da88..074532e741 100644
--- a/django/utils/decorators.py
+++ b/django/utils/decorators.py
@@ -16,7 +16,14 @@ def decorator_from_middleware(middleware_class):
                 result = middleware.process_view(request, view_func, **kwargs)
                 if result is not None:
                     return result
-            response = view_func(request, *args, **kwargs)
+            try:
+                response = view_func(request, *args, **kwargs)
+            except Exception, e:
+                if hasattr(middleware, 'process_exception'):
+                    result = middleware.process_exception(request, e)
+                    if result is not None:
+                        return result
+                raise e
             if hasattr(middleware, 'process_response'):
                 result = middleware.process_response(request, response)
                 if result is not None:
diff --git a/docs/middleware.txt b/docs/middleware.txt
index dfa1947bbd..33cb1a38e4 100644
--- a/docs/middleware.txt
+++ b/docs/middleware.txt
@@ -168,6 +168,19 @@ object returned by a Django view.
 the given ``response``, or it could create and return a brand-new
 ``HttpResponse``.
 
+process_exception
+-----------------
+
+Interface: ``process_exception(self, request, exception)``
+
+``request`` is an ``HttpRequest`` object. ``exception`` is an ``Exception``
+object raised by the view function.
+
+Django calls ``process_exception()`` when a view raises an exception.
+``process_exception()`` should return either ``None`` or an ``HttpResponse``
+object. If it returns an ``HttpResponse`` object, the response will be returned
+to the browser. Otherwise, default exception handling kicks in.
+
 Guidelines
 ----------