From 44ad691558c88ac54483030b2c8b749788c4600e Mon Sep 17 00:00:00 2001
From: Aymeric Augustin <aymeric.augustin@m4x.org>
Date: Thu, 5 Feb 2015 11:53:04 +0100
Subject: [PATCH] Fixed #24265 -- Preserved template backend loading
exceptions.
If importing or initializing a template backend fails, attempting to
access this template backend again must raise the same exception.
---
django/template/utils.py | 4 +++
tests/template_backends/test_utils.py | 37 +++++++++++++++++++++++++++
2 files changed, 41 insertions(+)
create mode 100644 tests/template_backends/test_utils.py
diff --git a/django/template/utils.py b/django/template/utils.py
index 3303c1ccb7..be2166810c 100644
--- a/django/template/utils.py
+++ b/django/template/utils.py
@@ -90,6 +90,10 @@ class EngineHandler(object):
"Could not find config for '{}' "
"in settings.TEMPLATES".format(alias))
+ # If importing or initializing the backend raises an exception,
+ # self._engines[alias] isn't set and this code may get executed
+ # again, so we must preserve the original params. See #24265.
+ params = params.copy()
backend = params.pop('BACKEND')
engine_cls = import_string(backend)
engine = engine_cls(params)
diff --git a/tests/template_backends/test_utils.py b/tests/template_backends/test_utils.py
new file mode 100644
index 0000000000..3d2de99015
--- /dev/null
+++ b/tests/template_backends/test_utils.py
@@ -0,0 +1,37 @@
+from django.core.exceptions import ImproperlyConfigured
+from django.template import engines
+from django.test import SimpleTestCase, override_settings
+
+
+class TemplateStringsTests(SimpleTestCase):
+
+ @override_settings(TEMPLATES=[{
+ 'BACKEND': 'raise.import.error',
+ }])
+ def test_backend_import_error(self):
+ """
+ Failing to import a backend keeps raising the original import error.
+
+ Regression test for #24265.
+ """
+ with self.assertRaises(ImportError):
+ engines.all()
+ with self.assertRaises(ImportError):
+ engines.all()
+
+ @override_settings(TEMPLATES=[{
+ 'BACKEND': 'django.template.backends.django.DjangoTemplates',
+ # Incorrect: APP_DIRS and loaders are mutually incompatible.
+ 'APP_DIRS': True,
+ 'OPTIONS': {'loaders': []},
+ }])
+ def test_backend_improperly_configured(self):
+ """
+ Failing to initialize a backend keeps raising the original exception.
+
+ Regression test for #24265.
+ """
+ with self.assertRaises(ImproperlyConfigured):
+ engines.all()
+ with self.assertRaises(ImproperlyConfigured):
+ engines.all()