Simplified caching of templatetags modules.

3 files changed, 16 insertions, 25 deletions

diff --git a/django/template/base.py b/django/template/base.py
index ee33dacda2..7c69e26088 100644
--- a/django/template/base.py
+++ b/django/template/base.py
@@ -10,6 +10,7 @@ from django.apps import apps
 from django.conf import settings
 from django.template.context import (BaseContext, Context, RequestContext,  # NOQA: imported for backwards compatibility
     ContextPopException)
+from django.utils import lru_cache
 from django.utils.deprecation import RemovedInDjango20Warning
 from django.utils.itercompat import is_iterable
 from django.utils.text import (smart_split, unescape_string_literal,
@@ -1296,32 +1297,27 @@ def import_library(taglib_module):
                                      "a variable named 'register'" %
                                      taglib_module)
 
-templatetags_modules = []
-
 
+@lru_cache.lru_cache()
 def get_templatetags_modules():
     """
     Return the list of all available template tag modules.
 
     Caches the result for faster access.
     """
-    global templatetags_modules
-    if not templatetags_modules:
-        _templatetags_modules = []
-        # Populate list once per process. Mutate the local list first, and
-        # then assign it to the global name to ensure there are no cases where
-        # two threads try to populate it simultaneously.
+    templatetags_modules_candidates = ['django.templatetags']
+    templatetags_modules_candidates += [
+        '%s.templatetags' % app_config.name
+        for app_config in apps.get_app_configs()]
 
-        templatetags_modules_candidates = ['django.templatetags']
-        templatetags_modules_candidates += ['%s.templatetags' % app_config.name
-            for app_config in apps.get_app_configs()]
-        for templatetag_module in templatetags_modules_candidates:
-            try:
-                import_module(templatetag_module)
-                _templatetags_modules.append(templatetag_module)
-            except ImportError:
-                continue
-        templatetags_modules = _templatetags_modules
+    templatetags_modules = []
+    for templatetag_module in templatetags_modules_candidates:
+        try:
+            import_module(templatetag_module)
+        except ImportError:
+            continue
+        else:
+            templatetags_modules.append(templatetag_module)
     return templatetags_modules
 
 
diff --git a/django/test/signals.py b/django/test/signals.py
index c38dd80688..d8c4aa93ae 100644
--- a/django/test/signals.py
+++ b/django/test/signals.py
@@ -37,8 +37,8 @@ def update_installed_apps(**kwargs):
         from django.core.management import get_commands
         get_commands.cache_clear()
         # Rebuild templatetags module cache.
-        from django.template import base as mod
-        mod.templatetags_modules = []
+        from django.template.base import get_templatetags_modules
+        get_templatetags_modules.cache_clear()
         # Rebuild get_app_template_dirs cache.
         from django.template.utils import get_app_template_dirs
         get_app_template_dirs.cache_clear()
diff --git a/tests/template_tests/tests.py b/tests/template_tests/tests.py
index b8097fbde1..80d7b727d6 100644
--- a/tests/template_tests/tests.py
+++ b/tests/template_tests/tests.py
@@ -1855,11 +1855,6 @@ class TemplateTagLoading(TestCase):
 
     def setUp(self):
         self.egg_dir = '%s/eggs' % os.path.dirname(upath(__file__))
-        self.old_tag_modules = template_base.templatetags_modules
-        template_base.templatetags_modules = []
-
-    def tearDown(self):
-        template_base.templatetags_modules = self.old_tag_modules
 
     def test_load_error(self):
         ttext = "{% load broken_tag %}"