Support for HTML error templates. Fixes #319.

docs/api-guide/renderers.md

@@ -257,6 +257,21 @@ In [the words of Roy Fielding][quote], "A REST API should spend almost all of it
 
 For good examples of custom media types, see GitHub's use of a custom [application/vnd.github+json] media type, and Mike Amundsen's IANA approved [application/vnd.collection+json] JSON-based hypermedia.
 
+## HTML error views
+
+Typically a renderer will behave the same regardless of if it's dealing with a regular response, or with a response caused by an exception being raised, such as an `Http404` or `PermissionDenied` exception, or a subclass of `APIException`.
+
+If you're using either the `TemplateHTMLRenderer` or the `StaticHTMLRenderer` and an exception is raised, the behavior is slightly different, and mirrors [Django's default handling of error views][django-error-views].
+
+Exceptions raised and handled by an HTML renderer will attempt to render using one of the following methods, by order of precedence.
+
+* Load and render a template named `{status_code}.html`.
+* Load and render a template named `api_exception.html`.
+* Render the HTTP status code and text, for example "404 Not Found".
+
+Templates will render with a `RequestContext` which includes the `status_code` and `details` keys.
+
+
 [cite]: https://docs.djangoproject.com/en/dev/ref/template-response/#the-rendering-process
 [conneg]: content-negotiation.md
 [browser-accept-headers]: http://www.gethifi.com/blog/browser-rest-http-accept-headers
@@ -265,3 +280,4 @@ For good examples of custom media types, see GitHub's use of a custom [applicati
 [quote]: http://roy.gbiv.com/untangled/2008/rest-apis-must-be-hypertext-driven
 [application/vnd.github+json]: http://developer.github.com/v3/media/
 [application/vnd.collection+json]: http://www.amundsen.com/media-types/collection/
+[django-error-views]: https://docs.djangoproject.com/en/dev/topics/http/views/#customizing-error-views

rest_framework/renderers.py

@@ -10,7 +10,7 @@ import copy
 import string
 from django import forms
 from django.http.multipartparser import parse_header
-from django.template import RequestContext, loader
+from django.template import RequestContext, loader, Template
 from django.utils import simplejson as json
 from rest_framework.compat import yaml
 from rest_framework.exceptions import ConfigurationError
@@ -162,6 +162,10 @@ class TemplateHTMLRenderer(BaseRenderer):
     media_type = 'text/html'
     format = 'html'
     template_name = None
+    exception_template_names = [
+        '%(status_code)s.html',
+        'api_exception.html'
+    ]
 
     def render(self, data, accepted_media_type=None, renderer_context=None):
         """
@@ -178,15 +182,21 @@ class TemplateHTMLRenderer(BaseRenderer):
         request = renderer_context['request']
         response = renderer_context['response']
 
-        template_names = self.get_template_names(response, view)
-        template = self.resolve_template(template_names)
-        context = self.resolve_context(data, request)
+        if response.exception:
+            template = self.get_exception_template(response)
+        else:
+            template_names = self.get_template_names(response, view)
+            template = self.resolve_template(template_names)
+
+        context = self.resolve_context(data, request, response)
         return template.render(context)
 
     def resolve_template(self, template_names):
         return loader.select_template(template_names)
 
-    def resolve_context(self, data, request):
+    def resolve_context(self, data, request, response):
+        if response.exception:
+            data['status_code'] = response.status_code
         return RequestContext(request, data)
 
     def get_template_names(self, response, view):
@@ -198,8 +208,21 @@ class TemplateHTMLRenderer(BaseRenderer):
             return view.get_template_names()
         raise ConfigurationError('Returned a template response with no template_name')
 
+    def get_exception_template(self, response):
+        template_names = [name % {'status_code': response.status_code}
+                          for name in self.exception_template_names]
 
-class StaticHTMLRenderer(BaseRenderer):
+        try:
+            # Try to find an appropriate error template
+            return self.resolve_template(template_names)
+        except:
+            # Fall back to using eg '404 Not Found'
+            return Template('%d %s' % (response.status_code,
+                                       response.status_text.title()))
+
+
+# Note, subclass TemplateHTMLRenderer simply for the exception behavior
+class StaticHTMLRenderer(TemplateHTMLRenderer):
     """
     An HTML renderer class that simply returns pre-rendered HTML.
 
@@ -216,6 +239,15 @@ class StaticHTMLRenderer(BaseRenderer):
     format = 'html'
 
     def render(self, data, accepted_media_type=None, renderer_context=None):
+        renderer_context = renderer_context or {}
+        response = renderer_context['response']
+
+        if response and response.exception:
+            request = renderer_context['request']
+            template = self.get_exception_template(response)
+            context = self.resolve_context(data, request, response)
+            return template.render(context)
+
         return data
 
 

rest_framework/response.py

@@ -9,7 +9,8 @@ class Response(SimpleTemplateResponse):
     """
 
     def __init__(self, data=None, status=200,
-                 template_name=None, headers=None):
+                 template_name=None, headers=None,
+                 exception=False):
         """
         Alters the init arguments slightly.
         For example, drop 'template_name', and instead use 'data'.
@@ -21,6 +22,7 @@ class Response(SimpleTemplateResponse):
         self.data = data
         self.headers = headers and headers[:] or []
         self.template_name = template_name
+        self.exception = exception
 
     @property
     def rendered_content(self):

rest_framework/tests/htmlrenderer.py

@@ -1,4 +1,6 @@
+from django.core.exceptions import PermissionDenied
 from django.conf.urls.defaults import patterns, url
+from django.http import Http404
 from django.test import TestCase
 from django.template import TemplateDoesNotExist, Template
 import django.template.loader
@@ -17,8 +19,22 @@ def example(request):
     return Response(data, template_name='example.html')
 
 
+@api_view(('GET',))
+@renderer_classes((TemplateHTMLRenderer,))
+def permission_denied(request):
+    raise PermissionDenied()
+
+
+@api_view(('GET',))
+@renderer_classes((TemplateHTMLRenderer,))
+def not_found(request):
+    raise Http404()
+
+
 urlpatterns = patterns('',
     url(r'^$', example),
+    url(r'^permission_denied$', permission_denied),
+    url(r'^not_found$', not_found),
 )
 
 
@@ -48,3 +64,52 @@ class TemplateHTMLRendererTests(TestCase):
         response = self.client.get('/')
         self.assertContains(response, "example: foobar")
         self.assertEquals(response['Content-Type'], 'text/html')
+
+    def test_not_found_html_view(self):
+        response = self.client.get('/not_found')
+        self.assertEquals(response.status_code, 404)
+        self.assertEquals(response.content, "404 Not Found")
+        self.assertEquals(response['Content-Type'], 'text/html')
+
+    def test_permission_denied_html_view(self):
+        response = self.client.get('/permission_denied')
+        self.assertEquals(response.status_code, 403)
+        self.assertEquals(response.content, "403 Forbidden")
+        self.assertEquals(response['Content-Type'], 'text/html')
+
+
+class TemplateHTMLRendererExceptionTests(TestCase):
+    urls = 'rest_framework.tests.htmlrenderer'
+
+    def setUp(self):
+        """
+        Monkeypatch get_template
+        """
+        self.get_template = django.template.loader.get_template
+
+        def get_template(template_name):
+            if template_name == '404.html':
+                return Template("404: {{ detail }}")
+            if template_name == '403.html':
+                return Template("403: {{ detail }}")
+            raise TemplateDoesNotExist(template_name)
+
+        django.template.loader.get_template = get_template
+
+    def tearDown(self):
+        """
+        Revert monkeypatching
+        """
+        django.template.loader.get_template = self.get_template
+
+    def test_not_found_html_view_with_template(self):
+        response = self.client.get('/not_found')
+        self.assertEquals(response.status_code, 404)
+        self.assertEquals(response.content, "404: Not found")
+        self.assertEquals(response['Content-Type'], 'text/html')
+
+    def test_permission_denied_html_view_with_template(self):
+        response = self.client.get('/permission_denied')
+        self.assertEquals(response.status_code, 403)
+        self.assertEquals(response.content, "403: Permission denied")
+        self.assertEquals(response['Content-Type'], 'text/html')

rest_framework/views.py

@@ -320,13 +320,17 @@ class APIView(View):
             self.headers['X-Throttle-Wait-Seconds'] = '%d' % exc.wait
 
         if isinstance(exc, exceptions.APIException):
-            return Response({'detail': exc.detail}, status=exc.status_code)
+            return Response({'detail': exc.detail},
+                            status=exc.status_code,
+                            exception=True)
         elif isinstance(exc, Http404):
             return Response({'detail': 'Not found'},
-                            status=status.HTTP_404_NOT_FOUND)
+                            status=status.HTTP_404_NOT_FOUND,
+                            exception=True)
         elif isinstance(exc, PermissionDenied):
             return Response({'detail': 'Permission denied'},
-                            status=status.HTTP_403_FORBIDDEN)
+                            status=status.HTTP_403_FORBIDDEN,
+                            exception=True)
         raise
 
     # Note: session based authentication is explicitly CSRF validated,