Fixed #26144 -- Warned when dumping proxy model without concrete parent.

django/core/management/commands/dumpdata.py

@@ -1,3 +1,5 @@
+import inspect
+import warnings
 from collections import OrderedDict
 
 from django.apps import apps
@@ -6,6 +8,10 @@ from django.core.management.base import BaseCommand, CommandError
 from django.db import DEFAULT_DB_ALIAS, router
 
 
+class ProxyModelWarning(Warning):
+    pass
+
+
 class Command(BaseCommand):
     help = ("Output the contents of the database as a fixture of the given "
             "format (using each model's default manager unless --all is "
@@ -132,9 +138,15 @@ class Command(BaseCommand):
             Collate the objects to be serialized. If count_only is True, just
             count the number of objects to be serialized.
             """
-            for model in serializers.sort_dependencies(app_list.items()):
+            models = serializers.sort_dependencies(app_list.items())
+            for model in models:
                 if model in excluded_models:
                     continue
+                if model._meta.proxy and inspect.getmro(model)[1] not in models:
+                    warnings.warn(
+                        "%s is a proxy model and won't be serialized." % model._meta.label,
+                        category=ProxyModelWarning,
+                    )
                 if not model._meta.proxy and router.allow_migrate_model(using, model):
                     if use_base_manager:
                         objects = model._base_manager

docs/releases/1.10.txt

@@ -245,6 +245,9 @@ Management Commands
 * The new :option:`shell --command` option lets you run a command as Django and
   exit, instead of opening the interactive shell.
 
+* Added a warning to :djadmin:`dumpdata` if a proxy model is specified (which
+  results in no output) without its concrete parent.
+
 Migrations
 ~~~~~~~~~~
 

tests/fixtures/models.py

@@ -92,6 +92,11 @@ class Spy(Person):
     cover_blown = models.BooleanField(default=False)
 
 
+class ProxySpy(Spy):
+    class Meta:
+        proxy = True
+
+
 @python_2_unicode_compatible
 class Visa(models.Model):
     person = models.ForeignKey(Person, models.CASCADE)

tests/fixtures/tests.py

@@ -4,12 +4,14 @@ import os
 import sys
 import tempfile
 import unittest
+import warnings
 
 from django.apps import apps
 from django.contrib.sites.models import Site
 from django.core import management
 from django.core.files.temp import NamedTemporaryFile
 from django.core.management import CommandError
+from django.core.management.commands.dumpdata import ProxyModelWarning
 from django.core.serializers.base import ProgressBar
 from django.db import IntegrityError, connection
 from django.test import (
@@ -18,7 +20,7 @@ from django.test import (
 from django.utils import six
 from django.utils.encoding import force_text
 
-from .models import Article, Spy, Tag, Visa
+from .models import Article, ProxySpy, Spy, Tag, Visa
 
 
 class TestCaseFixtureLoadingTests(TestCase):
@@ -476,6 +478,38 @@ class FixtureLoadingTests(DumpDataAssertMixin, TestCase):
             management.call_command('dumpdata', 'fixtures', **options)
             self.assertEqual(new_io.getvalue(), '')
 
+    def test_dumpdata_proxy_without_concrete(self):
+        """
+        A warning is displayed if a proxy model is dumped without its concrete
+        parent.
+        """
+        ProxySpy.objects.create(name='Paul')
+
+        with warnings.catch_warnings(record=True) as warning_list:
+            warnings.simplefilter('always')
+            self._dumpdata_assert(['fixtures.ProxySpy'], '[]')
+        warning = warning_list.pop()
+        self.assertEqual(warning.category, ProxyModelWarning)
+        self.assertEqual(
+            str(warning.message),
+            "fixtures.ProxySpy is a proxy model and won't be serialized."
+        )
+
+    def test_dumpdata_proxy_with_concrete(self):
+        """
+        A warning isn't displayed if a proxy model is dumped with its concrete
+        parent.
+        """
+        spy = ProxySpy.objects.create(name='Paul')
+
+        with warnings.catch_warnings(record=True) as warning_list:
+            warnings.simplefilter('always')
+            self._dumpdata_assert(
+                ['fixtures.ProxySpy', 'fixtures.Spy'],
+                '[{"pk": %d, "model": "fixtures.spy", "fields": {"cover_blown": false}}]' % spy.pk
+            )
+        self.assertEqual(len(warning_list), 0)
+
     def test_compress_format_loading(self):
         # Load fixture 4 (compressed), using format specification
         management.call_command('loaddata', 'fixture4.json', verbosity=0)