Fixed #17946 -- Fixed deserialization of self-referencing M2M fields

Thanks Philip Mountifield for the report and excellent analysis, and
Simon Charette for the review.

3 files changed, 15 insertions, 0 deletions

diff --git a/tests/fixtures_regress/fixtures/m2mtoself.json b/tests/fixtures_regress/fixtures/m2mtoself.json
new file mode 100644
index 0000000000..b904ba36e0
--- /dev/null
+++ b/tests/fixtures_regress/fixtures/m2mtoself.json
@@ -0,0 +1 @@
+[{"fields": {"parent": [1]}, "model": "fixtures_regress.m2mtoself", "pk": 1}]
diff --git a/tests/fixtures_regress/models.py b/tests/fixtures_regress/models.py
index f75b1e02d0..cd381e92bd 100644
--- a/tests/fixtures_regress/models.py
+++ b/tests/fixtures_regress/models.py
@@ -248,6 +248,10 @@ class Thingy(models.Model):
     name = models.CharField(max_length=255)
 
 
+class M2MToSelf(models.Model):
+    parent = models.ManyToManyField("self", blank=True, null=True)
+
+
 @python_2_unicode_compatible
 class BaseNKModel(models.Model):
     """
diff --git a/tests/fixtures_regress/tests.py b/tests/fixtures_regress/tests.py
index 89b8fb17ef..a91935af8f 100644
--- a/tests/fixtures_regress/tests.py
+++ b/tests/fixtures_regress/tests.py
@@ -487,6 +487,16 @@ class TestFixtures(TestCase):
             verbosity=0,
         )
 
+    def test_loaddata_with_m2m_to_self(self):
+        """
+        Regression test for ticket #17946.
+        """
+        management.call_command(
+            'loaddata',
+            'm2mtoself.json',
+            verbosity=0,
+        )
+
     @override_settings(FIXTURE_DIRS=[os.path.join(_cur_dir, 'fixtures_1'),
                                      os.path.join(_cur_dir, 'fixtures_1')])
     def test_fixture_dirs_with_duplicates(self):