Fixed #18990 -- Loaddata now complains if fixture doesn't exist

If the fixture doesn't exist, loaddata will output a warning.

The fixture named "initial_data" is exceptional though; if it
doesn't exist, the warning is not emitted. This allows syncdb and
flush management commands to attempt to load it without causing
spurious warnings.

Thanks to Derega, ptone, dirigeant and d1ffuz0r for contributions
to the ticket.

django/core/management/commands/loaddata.py

@@ -4,6 +4,7 @@ import os
 import gzip
 import zipfile
 from optparse import make_option
+import warnings
 
 from django.conf import settings
 from django.core import serializers
@@ -169,7 +170,7 @@ class Command(BaseCommand):
             label_found = label_found or found
 
         if fixture_name != 'initial_data' and not label_found:
-            raise CommandError("No fixture named '%s' found." % fixture_name)
+            warnings.warn("No fixture named '%s' found." % fixture_name)
 
     def process_dir(self, fixture_dir, fixture_name, compression_formats,
                     serialization_formats):

tests/fixtures/tests.py

@@ -1,5 +1,7 @@
 from __future__ import absolute_import
 
+import warnings
+
 from django.contrib.sites.models import Site
 from django.core import management
 from django.db import connection, IntegrityError
@@ -137,14 +139,18 @@ class FixtureLoadingTests(DumpDataAssertMixin, TestCase):
             '<Book: Music for all ages by Artist formerly known as "Prince" and Django Reinhardt>'
         ])
 
-        # Loading a fixture that doesn't exist results in an error
-        with self.assertRaises(management.CommandError):
+        # Loading a fixture that doesn't exist emits a warning
+        with warnings.catch_warnings(record=True) as w:
             management.call_command('loaddata', 'unknown.json', verbosity=0,
                 commit=False)
+        self.assertEqual(len(w), 1)
+        self.assertTrue(w[0].message, "No fixture named 'unknown' found.")
 
         # An attempt to load a nonexistent 'initial_data' fixture isn't an error
-        management.call_command('loaddata', 'initial_data.json', verbosity=0,
-            commit=False)
+        with warnings.catch_warnings(record=True) as w:
+            management.call_command('loaddata', 'initial_data.json', verbosity=0,
+                commit=False)
+        self.assertEqual(len(w), 0)
 
         # object list is unaffected
         self.assertQuerysetEqual(Article.objects.all(), [
@@ -279,10 +285,10 @@ class FixtureLoadingTests(DumpDataAssertMixin, TestCase):
 
     def test_unmatched_identifier_loading(self):
         # Try to load db fixture 3. This won't load because the database identifier doesn't match
-        with self.assertRaises(management.CommandError):
+        with warnings.catch_warnings(record=True):
             management.call_command('loaddata', 'db_fixture_3', verbosity=0, commit=False)
 
-        with self.assertRaises(management.CommandError):
+        with warnings.catch_warnings(record=True):
             management.call_command('loaddata', 'db_fixture_3', verbosity=0, using='default', commit=False)
         self.assertQuerysetEqual(Article.objects.all(), [])
 

tests/fixtures_model_package/tests.py

@@ -100,7 +100,10 @@ class FixtureTestCase(TestCase):
         )
 
         # Load a fixture that doesn't exist
-        management.call_command("loaddata", "unknown.json", verbosity=0, commit=False)
+        import warnings
+        with warnings.catch_warnings(record=True):
+            management.call_command("loaddata", "unknown.json", verbosity=0, commit=False)
+
         self.assertQuerysetEqual(
             Article.objects.all(), [
                 "Django conquers world!",

tests/fixtures_regress/tests.py

@@ -441,7 +441,8 @@ class TestFixtures(TestCase):
 
     def test_loaddata_not_existant_fixture_file(self):
         stdout_output = StringIO()
-        with self.assertRaises(management.CommandError):
+        import warnings
+        with warnings.catch_warnings(record=True):
             management.call_command(
                 'loaddata',
                 'this_fixture_doesnt_exist',