Serve simple error pages if HTML isn't required

tbx/core/tests/test_views.py

@@ -107,3 +107,25 @@ def test_setting_theme_on_one_site_sets_it_on_multiple_sites(self):
         # check theme is set on new site
         resp = self.client.get(f"http://{new_site.hostname}/")
         self.assertEqual(resp.context["MODE"], mode)
+
+
+class PageNotFoundTestCase(TestCase):
+    url = "/does-not-exist/"
+
+    def test_accept_html(self) -> None:
+        response = self.client.get(self.url, headers={"Accept": "text/html"})
+        self.assertEqual(response.status_code, 404)
+        self.assertIn("text/html", response.headers["content-type"])
+        self.assertEqual(response.headers["Vary"], "Accept, Cookie")
+
+    def test_accept_text(self) -> None:
+        response = self.client.get(self.url, headers={"Accept": "text/plain"})
+        self.assertEqual(response.status_code, 404)
+        self.assertIn("text/plain", response.headers["content-type"])
+        self.assertEqual(response.headers["Vary"], "Accept")
+
+    def test_simple_when_doesnt_accept_html(self) -> None:
+        response = self.client.get(self.url, headers={"Accept": "text/css"})
+        self.assertEqual(response.status_code, 404)
+        self.assertIn("text/plain", response.headers["content-type"])
+        self.assertEqual(response.headers["Vary"], "Accept")

tbx/core/utils/views.py

@@ -1,9 +1,34 @@
+from django.http import HttpResponseNotFound, HttpResponseServerError
 from django.views import defaults
+from django.views.decorators.vary import vary_on_headers
 
 
+def show_html_error_page(request):
+    """
+    - If HTML is the most preferred type, show HTML.
+    - If plain text is most preferred, don't show HTML
+    - If neither are accepted, don't show HTML
+    """
+    return request.get_preferred_type(["text/html", "text/plain"]) == "text/html"
+
+
+@vary_on_headers("Accept")
 def page_not_found(request, exception, template_name="patterns/pages/errors/404.html"):
-    return defaults.page_not_found(request, exception, template_name)
+    if show_html_error_page(request):
+        return defaults.page_not_found(request, exception, template_name)
 
+    # Serve a simpler, cheaper 404 page if possible
+    return HttpResponseNotFound(
+        "Page not found", content_type="text/plain; charset=utf-8"
+    )
 
+
+@vary_on_headers("Accept")
 def server_error(request, template_name="patterns/pages/errors/500.html"):
-    return defaults.server_error(request, template_name)
+    if show_html_error_page(request):
+        return defaults.server_error(request, template_name)
+
+    # Serve a simpler, cheaper 500 page if possible
+    return HttpResponseServerError(
+        "Server error", content_type="text/plain; charset=utf-8"
+    )

tbx/urls.py

@@ -17,6 +17,7 @@
     get_default_cache_control_decorator,
     get_default_cache_control_method_decorator,
 )
+from tbx.core.utils.views import page_not_found, server_error
 from tbx.core.views import robots, switch_mode
 
 
@@ -35,7 +36,6 @@
 if settings.DEBUG:
     from django.conf.urls.static import static
     from django.contrib.staticfiles.urls import staticfiles_urlpatterns
-    from django.views.generic import TemplateView
 
     # Serve static and media files from development server
     urlpatterns += staticfiles_urlpatterns()
@@ -44,14 +44,8 @@
     # Add views for testing 404 and 500 templates
     urlpatterns += [
         # Add views for testing 404 and 500 templates
-        path(
-            "test404/",
-            TemplateView.as_view(template_name="patterns/pages/errors/404.html"),
-        ),
-        path(
-            "test500/",
-            TemplateView.as_view(template_name="patterns/pages/errors/500.html"),
-        ),
+        path("test404/", page_not_found),
+        path("test500/", server_error),
     ]
 
     # Django Debug Toolbar
@@ -104,5 +98,5 @@
 )
 
 # Error handlers
-handler404 = "tbx.core.utils.views.page_not_found"
-handler500 = "tbx.core.utils.views.server_error"
+handler404 = page_not_found
+handler500 = server_error