Fixed #35229 -- Made URL custom error handler check run once.

1 files changed, 42 insertions, 0 deletions

diff --git a/django/core/checks/urls.py b/django/core/checks/urls.py
index 34eff9671d..aef2bfebb0 100644
--- a/django/core/checks/urls.py
+++ b/django/core/checks/urls.py
@@ -1,6 +1,8 @@
+import inspect
 from collections import Counter
 
 from django.conf import settings
+from django.core.exceptions import ViewDoesNotExist
 
 from . import Error, Tags, Warning, register
 
@@ -115,3 +117,43 @@ def E006(name):
         "The {} setting must end with a slash.".format(name),
         id="urls.E006",
     )
+
+
+@register(Tags.urls)
+def check_custom_error_handlers(app_configs, **kwargs):
+    if not getattr(settings, "ROOT_URLCONF", None):
+        return []
+
+    from django.urls import get_resolver
+
+    resolver = get_resolver()
+
+    errors = []
+    # All handlers take (request, exception) arguments except handler500
+    # which takes (request).
+    for status_code, num_parameters in [(400, 2), (403, 2), (404, 2), (500, 1)]:
+        try:
+            handler = resolver.resolve_error_handler(status_code)
+        except (ImportError, ViewDoesNotExist) as e:
+            path = getattr(resolver.urlconf_module, "handler%s" % status_code)
+            msg = (
+                "The custom handler{status_code} view '{path}' could not be "
+                "imported."
+            ).format(status_code=status_code, path=path)
+            errors.append(Error(msg, hint=str(e), id="urls.E008"))
+            continue
+        signature = inspect.signature(handler)
+        args = [None] * num_parameters
+        try:
+            signature.bind(*args)
+        except TypeError:
+            msg = (
+                "The custom handler{status_code} view '{path}' does not "
+                "take the correct number of arguments ({args})."
+            ).format(
+                status_code=status_code,
+                path=handler.__module__ + "." + handler.__qualname__,
+                args="request, exception" if num_parameters == 2 else "request",
+            )
+            errors.append(Error(msg, id="urls.E007"))
+    return errors