Fixed #17667 -- Prevented app loading from skipping nonexistent apps after the first try

Thanks ea2100@ for the report and akaariai for the patch.

1 files changed, 26 insertions, 4 deletions

diff --git a/tests/app_loading/tests.py b/tests/app_loading/tests.py
index bba2b234a2..dc25899646 100644
--- a/tests/app_loading/tests.py
+++ b/tests/app_loading/tests.py
@@ -7,7 +7,8 @@ import time
 from unittest import TestCase
 
 from django.conf import Settings
-from django.db.models.loading import cache, load_app, get_model, get_models
+from django.db.models.loading import cache, load_app, get_model, get_models, AppCache
+from django.test.utils import override_settings
 from django.utils._os import upath
 
 
@@ -61,12 +62,33 @@ class EggLoadingTest(TestCase):
         egg_name = '%s/brokenapp.egg' % self.egg_dir
         sys.path.append(egg_name)
         self.assertRaises(ImportError, load_app, 'broken_app')
+        raised = None
         try:
             load_app('broken_app')
         except ImportError as e:
-            # Make sure the message is indicating the actual
-            # problem in the broken app.
-            self.assertTrue("modelz" in e.args[0])
+            raised = e
+
+        # Make sure the message is indicating the actual
+        # problem in the broken app.
+        self.assertTrue(raised is not None)
+        self.assertTrue("modelz" in raised.args[0])
+
+    def test_missing_app(self):
+        """
+        Test that repeated app loading doesn't succeed in case there is an
+        error. Refs #17667.
+        """
+        # AppCache is a Borg, so we can instantiate one and change its
+        # loaded to False to force the following code to actually try to
+        # populate the cache.
+        a = AppCache()
+        a.loaded = False
+        try:
+            with override_settings(INSTALLED_APPS=('notexists',)):
+                self.assertRaises(ImportError, get_model, 'notexists', 'nomodel', seed_cache=True)
+                self.assertRaises(ImportError, get_model, 'notexists', 'nomodel', seed_cache=True)
+        finally:
+            a.loaded = True
 
 
 class GetModelsTest(TestCase):