Fixed #19049 -- Ensure that swapped models aren't included in reverse field caches.

Thanks to Ivan Virabyan for the report.

tests/modeltests/invalid_models/invalid_models/models.py

@@ -303,13 +303,28 @@ class SwappedModel(models.Model):
     References to this model *should* raise a validation error.
     Requires TEST_SWAPPED_MODEL to be defined in the test environment;
     this is guaranteed by the test runner using @override_settings.
+
+    The foreign keys and m2m relations on this model *shouldn't*
+    install related accessors, so there shouldn't be clashes with
+    the equivalent names on the replacement.
     """
     name = models.CharField(max_length=100)
 
+    foreign = models.ForeignKey(Target, related_name='swappable_fk_set')
+    m2m = models.ManyToManyField(Target, related_name='swappable_m2m_set')
+
     class Meta:
         swappable = 'TEST_SWAPPED_MODEL'
 
 
+class ReplacementModel(models.Model):
+    """A replacement model for swapping purposes."""
+    name = models.CharField(max_length=100)
+
+    foreign = models.ForeignKey(Target, related_name='swappable_fk_set')
+    m2m = models.ManyToManyField(Target, related_name='swappable_m2m_set')
+
+
 class BadSwappableValue(models.Model):
     """A model that can be swapped out; during testing, the swappable
     value is not of the format app.model

tests/modeltests/invalid_models/tests.py

@@ -37,7 +37,7 @@ class InvalidModelTestCase(unittest.TestCase):
     # easier to set this up as an override than to require every developer
     # to specify a value in their test settings.
     @override_settings(
-        TEST_SWAPPED_MODEL='invalid_models.Target',
+        TEST_SWAPPED_MODEL='invalid_models.ReplacementModel',
         TEST_SWAPPED_MODEL_BAD_VALUE='not-a-model',
         TEST_SWAPPED_MODEL_BAD_MODEL='not_an_app.Target',
     )