Refs #26601 -- Refactored BaseHandler to prepare for new-style middleware.

2 files changed, 164 insertions, 126 deletions

diff --git a/django/core/handlers/base.py b/django/core/handlers/base.py
index 93b8f04cac..65cb59357c 100644
--- a/django/core/handlers/base.py
+++ b/django/core/handlers/base.py
@@ -5,18 +5,14 @@ import sys
 import types
 import warnings
 
-from django import http
 from django.conf import settings
 from django.core import signals
-from django.core.exceptions import (
-    MiddlewareNotUsed, PermissionDenied, SuspiciousOperation,
-)
+from django.core.exceptions import MiddlewareNotUsed
 from django.db import connections, transaction
-from django.http.multipartparser import MultiPartParserError
-from django.urls import get_resolver, set_urlconf
+from django.middleware.exception import ExceptionMiddleware
+from django.urls import get_resolver, get_urlconf, set_urlconf
 from django.utils import six
 from django.utils.deprecation import RemovedInDjango20Warning
-from django.utils.encoding import force_text
 from django.utils.module_loading import import_string
 from django.views import debug
 
@@ -31,6 +27,7 @@ class BaseHandler(object):
         self._template_response_middleware = None
         self._response_middleware = None
         self._exception_middleware = None
+        self._middleware_chain = None
 
     def load_middleware(self):
         """
@@ -38,12 +35,13 @@ class BaseHandler(object):
 
         Must be called after the environment is fixed (see __call__ in subclasses).
         """
+        self._request_middleware = []
         self._view_middleware = []
         self._template_response_middleware = []
         self._response_middleware = []
         self._exception_middleware = []
 
-        request_middleware = []
+        handler = self._legacy_get_response
         for middleware_path in settings.MIDDLEWARE_CLASSES:
             mw_class = import_string(middleware_path)
             try:
@@ -57,7 +55,7 @@ class BaseHandler(object):
                 continue
 
             if hasattr(mw_instance, 'process_request'):
-                request_middleware.append(mw_instance.process_request)
+                self._request_middleware.append(mw_instance.process_request)
             if hasattr(mw_instance, 'process_view'):
                 self._view_middleware.append(mw_instance.process_view)
             if hasattr(mw_instance, 'process_template_response'):
@@ -67,9 +65,11 @@ class BaseHandler(object):
             if hasattr(mw_instance, 'process_exception'):
                 self._exception_middleware.insert(0, mw_instance.process_exception)
 
+        handler = ExceptionMiddleware(handler, self)
+
         # We only assign to this when initialization is complete as it is used
         # as a flag for initialization being complete.
-        self._request_middleware = request_middleware
+        self._middleware_chain = handler
 
     def make_view_atomic(self, view):
         non_atomic_requests = getattr(view, '_non_atomic_requests', set())
@@ -100,121 +100,11 @@ class BaseHandler(object):
         return response
 
     def get_response(self, request):
-        "Returns an HttpResponse object for the given HttpRequest"
-
-        # Setup default url resolver for this thread, this code is outside
-        # the try/except so we don't get a spurious "unbound local
-        # variable" exception in the event an exception is raised before
-        # resolver is set
-        urlconf = settings.ROOT_URLCONF
-        set_urlconf(urlconf)
-        resolver = get_resolver(urlconf)
-        # Use a flag to check if the response was rendered to prevent
-        # multiple renderings or to force rendering if necessary.
-        response_is_rendered = False
-        try:
-            response = None
-            # Apply request middleware
-            for middleware_method in self._request_middleware:
-                response = middleware_method(request)
-                if response:
-                    break
-
-            if response is None:
-                if hasattr(request, 'urlconf'):
-                    # Reset url resolver with a custom URLconf.
-                    urlconf = request.urlconf
-                    set_urlconf(urlconf)
-                    resolver = get_resolver(urlconf)
-
-                resolver_match = resolver.resolve(request.path_info)
-                callback, callback_args, callback_kwargs = resolver_match
-                request.resolver_match = resolver_match
-
-                # Apply view middleware
-                for middleware_method in self._view_middleware:
-                    response = middleware_method(request, callback, callback_args, callback_kwargs)
-                    if response:
-                        break
-
-            if response is None:
-                wrapped_callback = self.make_view_atomic(callback)
-                try:
-                    response = wrapped_callback(request, *callback_args, **callback_kwargs)
-                except Exception as e:
-                    response = self.process_exception_by_middleware(e, request)
+        """Return an HttpResponse object for the given HttpRequest."""
+        # Setup default url resolver for this thread
+        set_urlconf(settings.ROOT_URLCONF)
 
-            # Complain if the view returned None (a common error).
-            if response is None:
-                if isinstance(callback, types.FunctionType):    # FBV
-                    view_name = callback.__name__
-                else:                                           # CBV
-                    view_name = callback.__class__.__name__ + '.__call__'
-                raise ValueError(
-                    "The view %s.%s didn't return an HttpResponse object. It "
-                    "returned None instead." % (callback.__module__, view_name)
-                )
-
-            # If the response supports deferred rendering, apply template
-            # response middleware and then render the response
-            if hasattr(response, 'render') and callable(response.render):
-                for middleware_method in self._template_response_middleware:
-                    response = middleware_method(request, response)
-                    # Complain if the template response middleware returned None (a common error).
-                    if response is None:
-                        raise ValueError(
-                            "%s.process_template_response didn't return an "
-                            "HttpResponse object. It returned None instead."
-                            % (middleware_method.__self__.__class__.__name__)
-                        )
-                try:
-                    response = response.render()
-                except Exception as e:
-                    response = self.process_exception_by_middleware(e, request)
-
-                response_is_rendered = True
-
-        except http.Http404 as exc:
-            if settings.DEBUG:
-                response = debug.technical_404_response(request, exc)
-            else:
-                response = self.get_exception_response(request, resolver, 404, exc)
-
-        except PermissionDenied as exc:
-            logger.warning(
-                'Forbidden (Permission denied): %s', request.path,
-                extra={'status_code': 403, 'request': request},
-            )
-            response = self.get_exception_response(request, resolver, 403, exc)
-
-        except MultiPartParserError as exc:
-            logger.warning(
-                'Bad request (Unable to parse request body): %s', request.path,
-                extra={'status_code': 400, 'request': request},
-            )
-            response = self.get_exception_response(request, resolver, 400, exc)
-
-        except SuspiciousOperation as exc:
-            # The request logger receives events for any problematic request
-            # The security logger receives events for all SuspiciousOperations
-            security_logger = logging.getLogger('django.security.%s' % exc.__class__.__name__)
-            security_logger.error(
-                force_text(exc),
-                extra={'status_code': 400, 'request': request},
-            )
-            if settings.DEBUG:
-                return debug.technical_500_response(request, *sys.exc_info(), status_code=400)
-
-            response = self.get_exception_response(request, resolver, 400, exc)
-
-        except SystemExit:
-            # Allow sys.exit() to actually exit. See tickets #1023 and #4701
-            raise
-
-        except Exception:  # Handle everything else.
-            # Get the exception info now, in case another exception is thrown later.
-            signals.got_request_exception.send(sender=self.__class__, request=request)
-            response = self.handle_uncaught_exception(request, resolver, sys.exc_info())
+        response = self._middleware_chain(request)
 
         try:
             # Apply response middleware, regardless of the response
@@ -228,13 +118,13 @@ class BaseHandler(object):
                         % (middleware_method.__self__.__class__.__name__))
         except Exception:  # Any exception should be gathered and handled
             signals.got_request_exception.send(sender=self.__class__, request=request)
-            response = self.handle_uncaught_exception(request, resolver, sys.exc_info())
+            response = self.handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
 
         response._closable_objects.append(request)
 
         # If the exception handler returns a TemplateResponse that has not
         # been rendered, force it to be rendered.
-        if not response_is_rendered and callable(getattr(response, 'render', None)):
+        if not getattr(response, 'is_rendered', True) and callable(getattr(response, 'render', None)):
             response = response.render()
 
         if response.status_code == 404:
@@ -245,6 +135,64 @@ class BaseHandler(object):
 
         return response
 
+    def _get_response(self, request):
+        response = None
+
+        if hasattr(request, 'urlconf'):
+            urlconf = request.urlconf
+            set_urlconf(urlconf)
+            resolver = get_resolver(urlconf)
+        else:
+            resolver = get_resolver()
+
+        resolver_match = resolver.resolve(request.path_info)
+        callback, callback_args, callback_kwargs = resolver_match
+        request.resolver_match = resolver_match
+
+        # Apply view middleware
+        for middleware_method in self._view_middleware:
+            response = middleware_method(request, callback, callback_args, callback_kwargs)
+            if response:
+                return response
+
+        wrapped_callback = self.make_view_atomic(callback)
+        try:
+            response = wrapped_callback(request, *callback_args, **callback_kwargs)
+        except Exception as e:
+            response = self.process_exception_by_middleware(e, request)
+
+        # Complain if the view returned None (a common error).
+        if response is None:
+            if isinstance(callback, types.FunctionType):    # FBV
+                view_name = callback.__name__
+            else:                                           # CBV
+                view_name = callback.__class__.__name__ + '.__call__'
+
+            raise ValueError(
+                "The view %s.%s didn't return an HttpResponse object. It "
+                "returned None instead." % (callback.__module__, view_name)
+            )
+
+        # If the response supports deferred rendering, apply template
+        # response middleware and then render the response
+        elif hasattr(response, 'render') and callable(response.render):
+            for middleware_method in self._template_response_middleware:
+                response = middleware_method(request, response)
+                # Complain if the template response middleware returned None (a common error).
+                if response is None:
+                    raise ValueError(
+                        "%s.process_template_response didn't return an "
+                        "HttpResponse object. It returned None instead."
+                        % (middleware_method.__self__.__class__.__name__)
+                    )
+
+            try:
+                response = response.render()
+            except Exception as e:
+                response = self.process_exception_by_middleware(e, request)
+
+        return response
+
     def process_exception_by_middleware(self, exception, request):
         """
         Pass the exception to the exception middleware. If no middleware
@@ -284,3 +232,15 @@ class BaseHandler(object):
         # Return an HttpResponse that displays a friendly error message.
         callback, param_dict = resolver.resolve_error_handler(500)
         return callback(request, **param_dict)
+
+    def _legacy_get_response(self, request):
+        response = None
+        # Apply request middleware
+        for middleware_method in self._request_middleware:
+            response = middleware_method(request)
+            if response:
+                break
+
+        if response is None:
+            response = self._get_response(request)
+        return response
diff --git a/django/middleware/exception.py b/django/middleware/exception.py
new file mode 100644
index 0000000000..437a82cf26
--- /dev/null
+++ b/django/middleware/exception.py
@@ -0,0 +1,78 @@
+from __future__ import unicode_literals
+
+import logging
+import sys
+
+from django.conf import settings
+from django.core import signals
+from django.core.exceptions import PermissionDenied, SuspiciousOperation
+from django.http import Http404
+from django.http.multipartparser import MultiPartParserError
+from django.urls import get_resolver, get_urlconf
+from django.utils.encoding import force_text
+from django.views import debug
+
+logger = logging.getLogger('django.request')
+
+
+class ExceptionMiddleware(object):
+    """
+    Convert selected exceptions to HTTP responses.
+
+    For example, convert Http404 to a 404 response either through handler404
+    or through the debug view if settings.DEBUG=True. To ensure that
+    exceptions raised by other middleware are converted to the appropriate
+    response, this middleware is always automatically applied as the outermost
+    middleware.
+    """
+    def __init__(self, get_response, handler=None):
+        from django.core.handlers.base import BaseHandler
+        self.get_response = get_response
+        self.handler = handler or BaseHandler()
+
+    def __call__(self, request):
+        try:
+            response = self.get_response(request)
+        except Http404 as exc:
+            if settings.DEBUG:
+                response = debug.technical_404_response(request, exc)
+            else:
+                response = self.handler.get_exception_response(request, get_resolver(get_urlconf()), 404, exc)
+
+        except PermissionDenied as exc:
+            logger.warning(
+                'Forbidden (Permission denied): %s', request.path,
+                extra={'status_code': 403, 'request': request},
+            )
+            response = self.handler.get_exception_response(request, get_resolver(get_urlconf()), 403, exc)
+
+        except MultiPartParserError as exc:
+            logger.warning(
+                'Bad request (Unable to parse request body): %s', request.path,
+                extra={'status_code': 400, 'request': request},
+            )
+            response = self.handler.get_exception_response(request, get_resolver(get_urlconf()), 400, exc)
+
+        except SuspiciousOperation as exc:
+            # The request logger receives events for any problematic request
+            # The security logger receives events for all SuspiciousOperations
+            security_logger = logging.getLogger('django.security.%s' % exc.__class__.__name__)
+            security_logger.error(
+                force_text(exc),
+                extra={'status_code': 400, 'request': request},
+            )
+            if settings.DEBUG:
+                return debug.technical_500_response(request, *sys.exc_info(), status_code=400)
+
+            response = self.handler.get_exception_response(request, get_resolver(get_urlconf()), 400, exc)
+
+        except SystemExit:
+            # Allow sys.exit() to actually exit. See tickets #1023 and #4701
+            raise
+
+        except Exception:  # Handle everything else.
+            # Get the exception info now, in case another exception is thrown later.
+            signals.got_request_exception.send(sender=self.handler.__class__, request=request)
+            response = self.handler.handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
+
+        return response