Fixed #27612 -- Added a check for duplicate URL instance namespaces.

1 files changed, 40 insertions, 1 deletions

diff --git a/django/core/checks/urls.py b/django/core/checks/urls.py
index a1e9929084..8187a4e561 100644
--- a/django/core/checks/urls.py
+++ b/django/core/checks/urls.py
@@ -1,9 +1,11 @@
 from __future__ import unicode_literals
 
+from collections import Counter
+
 from django.conf import settings
 from django.utils import six
 
-from . import Error, Tags, register
+from . import Error, Tags, Warning, register
 
 
 @register(Tags.urls)
@@ -28,6 +30,43 @@ def check_resolver(resolver):
         return []
 
 
+@register(Tags.urls)
+def check_url_namespaces_unique(app_configs, **kwargs):
+    """
+    Warn if URL namespaces used in applications aren't unique.
+    """
+    if not getattr(settings, 'ROOT_URLCONF', None):
+        return []
+
+    from django.urls import get_resolver
+    resolver = get_resolver()
+    all_namespaces = _load_all_namespaces(resolver)
+    counter = Counter(all_namespaces)
+    non_unique_namespaces = [n for n, count in counter.items() if count > 1]
+    errors = []
+    for namespace in non_unique_namespaces:
+        errors.append(Warning(
+            "URL namespace '{}' isn't unique. You may not be able to reverse "
+            "all URLs in this namespace".format(namespace),
+            id="urls.W005",
+        ))
+    return errors
+
+
+def _load_all_namespaces(resolver):
+    """
+    Recursively load all namespaces from URL patterns.
+    """
+    url_patterns = getattr(resolver, 'url_patterns', [])
+    namespaces = [
+        url.namespace for url in url_patterns
+        if getattr(url, 'namespace', None) is not None
+    ]
+    for pattern in url_patterns:
+        namespaces.extend(_load_all_namespaces(pattern))
+    return namespaces
+
+
 def get_warning_for_invalid_pattern(pattern):
     """
     Return a list containing a warning that the pattern is invalid.