From 05c578bc1f6ab09ade17a29f79d7244b7acfb58f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Ko=C5=82odziej?= <p.kolodziej@gmail.com>
Date: Fri, 28 Sep 2018 01:49:37 +0200
Subject: [PATCH] Fixed #29796 -- Added system check for STATICFILES_DIRS
 prefix ending with a slash.

---
 django/contrib/staticfiles/finders.py  |  8 +++++++-
 docs/ref/checks.txt                    |  2 ++
 tests/staticfiles_tests/test_checks.py | 10 ++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/django/contrib/staticfiles/finders.py b/django/contrib/staticfiles/finders.py
index afce4ca637..8d8f1cb983 100644
--- a/django/contrib/staticfiles/finders.py
+++ b/django/contrib/staticfiles/finders.py
@@ -78,7 +78,13 @@ class FileSystemFinder(BaseFinder):
             ))
         for root in settings.STATICFILES_DIRS:
             if isinstance(root, (list, tuple)):
-                _, root = root
+                prefix, root = root
+                if prefix.endswith('/'):
+                    errors.append(Error(
+                        'The prefix %r in the STATICFILES_DIRS setting must '
+                        'not end with a slash.' % prefix,
+                        id='staticfiles.E003',
+                    ))
             if settings.STATIC_ROOT and os.path.abspath(settings.STATIC_ROOT) == os.path.abspath(root):
                 errors.append(Error(
                     'The STATICFILES_DIRS setting should not contain the '
diff --git a/docs/ref/checks.txt b/docs/ref/checks.txt
index 6895a93eff..67813067f2 100644
--- a/docs/ref/checks.txt
+++ b/docs/ref/checks.txt
@@ -731,3 +731,5 @@ configured:
   or list.
 * **staticfiles.E002**: The :setting:`STATICFILES_DIRS` setting should not
   contain the :setting:`STATIC_ROOT` setting.
+* **staticfiles.E003**: The prefix ``<prefix>`` in the
+  :setting:`STATICFILES_DIRS` setting must not end with a slash.
diff --git a/tests/staticfiles_tests/test_checks.py b/tests/staticfiles_tests/test_checks.py
index 0fe432b5c7..d5dc90b781 100644
--- a/tests/staticfiles_tests/test_checks.py
+++ b/tests/staticfiles_tests/test_checks.py
@@ -75,3 +75,13 @@ class FindersCheckTests(SimpleTestCase):
                 id='staticfiles.E002',
             )
         ])
+
+    @override_settings(STATICFILES_DIRS=[('prefix/', '/fake/path')])
+    def test_prefix_contains_trailing_slash(self):
+        self.assertEqual(check_finders(None), [
+            Error(
+                "The prefix 'prefix/' in the STATICFILES_DIRS setting must "
+                "not end with a slash.",
+                id='staticfiles.E003',
+            )
+        ])