Fixed #18213 -- Allowed empty fixtures (emit a warning rather than raising an exception).

django/core/management/commands/loaddata.py

@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 import glob
 import gzip
 import os
+import warnings
 import zipfile
 from optparse import make_option
 import warnings
@@ -156,12 +157,13 @@ class Command(BaseCommand):
             finally:
                 fixture.close()
 
-            # If the fixture we loaded contains 0 objects, assume that an
+            # Warn if the fixture we loaded contains 0 objects.
-            # error was encountered during fixture loading.
             if objects_in_fixture == 0:
-                raise CommandError(
+                warnings.warn(
-                        "No fixture data found for '%s'. "
+                    "No fixture data found for '%s'. (File format may be "
-                        "(File format may be invalid.)" % fixture_name)
+                    "invalid.)" % fixture_name,
+                    RuntimeWarning
+                )
 
     def _find_fixtures(self, fixture_label):
         """

docs/releases/1.7.txt

@@ -113,6 +113,9 @@ Miscellaneous
   :attr:`~django.forms.formsets.BaseFormSet.can_delete` for instructions on how
   to manually delete objects from deleted forms.
 
+* Loading empty fixtures emits a ``RuntimeWarning`` rather than raising
+  :class:`~django.core.management.CommandError`.
+
 Features deprecated in 1.7
 ==========================
 

tests/fixtures_regress/tests.py

@@ -181,55 +181,68 @@ class TestFixtures(TestCase):
         """
         Test for ticket #4371 -- Loading a fixture file with invalid data
         using explicit filename.
-        Validate that error conditions are caught correctly
+        Test for ticket #18213 -- warning conditions are caught correctly
         """
-        with six.assertRaisesRegex(self, management.CommandError,
+        with warnings.catch_warnings(record=True) as warning_list:
-                "No fixture data found for 'bad_fixture2'. \(File format may be invalid.\)"):
+            warnings.simplefilter("always")
             management.call_command(
                 'loaddata',
                 'bad_fixture2.xml',
                 verbosity=0,
             )
+            warning = warning_list.pop()
+            self.assertEqual(warning.category, RuntimeWarning)
+            self.assertEqual(str(warning.message), "No fixture data found for 'bad_fixture2'. (File format may be invalid.)")
 
     def test_invalid_data_no_ext(self):
         """
         Test for ticket #4371 -- Loading a fixture file with invalid data
         without file extension.
-        Validate that error conditions are caught correctly
+        Test for ticket #18213 -- warning conditions are caught correctly
         """
-        with six.assertRaisesRegex(self, management.CommandError,
+        with warnings.catch_warnings(record=True) as warning_list:
-                "No fixture data found for 'bad_fixture2'. \(File format may be invalid.\)"):
+            warnings.simplefilter("always")
             management.call_command(
                 'loaddata',
                 'bad_fixture2',
                 verbosity=0,
             )
+            warning = warning_list.pop()
+            self.assertEqual(warning.category, RuntimeWarning)
+            self.assertEqual(str(warning.message), "No fixture data found for 'bad_fixture2'. (File format may be invalid.)")
 
     def test_empty(self):
         """
-        Test for ticket #4371 -- Loading a fixture file with no data returns an error.
+        Test for ticket #18213 -- Loading a fixture file with no data output a warning.
-        Validate that error conditions are caught correctly
+        Previously empty fixture raises an error exception, see ticket #4371.
         """
-        with six.assertRaisesRegex(self, management.CommandError,
+        with warnings.catch_warnings(record=True) as warning_list:
-                "No fixture data found for 'empty'. \(File format may be invalid.\)"):
+            warnings.simplefilter("always")
             management.call_command(
                 'loaddata',
                 'empty',
                 verbosity=0,
             )
+            warning = warning_list.pop()
+            self.assertEqual(warning.category, RuntimeWarning)
+            self.assertEqual(str(warning.message), "No fixture data found for 'empty'. (File format may be invalid.)")
 
     def test_error_message(self):
         """
-        (Regression for #9011 - error message is correct)
+        Regression for #9011 - error message is correct.
+        Change from error to warning for ticket #18213.
         """
-        with six.assertRaisesRegex(self, management.CommandError,
+        with warnings.catch_warnings(record=True) as warning_list:
-                "^No fixture data found for 'bad_fixture2'. \(File format may be invalid.\)$"):
+            warnings.simplefilter("always")
             management.call_command(
                 'loaddata',
                 'bad_fixture2',
                 'animal',
                 verbosity=0,
             )
+            warning = warning_list.pop()
+            self.assertEqual(warning.category, RuntimeWarning)
+            self.assertEqual(str(warning.message), "No fixture data found for 'bad_fixture2'. (File format may be invalid.)")
 
     def test_pg_sequence_resetting_checks(self):
         """