Fixed #32676 -- Prevented migrations from rendering related field attributes when not passed during initialization.

Thanks Simon Charette for the implementation idea.

4 files changed, 80 insertions, 13 deletions

diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index 899ae8efe8..a0e8da10fd 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -89,6 +89,18 @@ class RelatedField(FieldCacheMixin, Field):
     many_to_many = False
     many_to_one = False
 
+    def __init__(
+        self,
+        related_name=None,
+        related_query_name=None,
+        limit_choices_to=None,
+        **kwargs,
+    ):
+        self._related_name = related_name
+        self._related_query_name = related_query_name
+        self._limit_choices_to = limit_choices_to
+        super().__init__(**kwargs)
+
     @cached_property
     def related_model(self):
         # Can't cache this property until all the models are loaded.
@@ -319,12 +331,12 @@ class RelatedField(FieldCacheMixin, Field):
 
     def deconstruct(self):
         name, path, args, kwargs = super().deconstruct()
-        if self.remote_field.limit_choices_to:
-            kwargs['limit_choices_to'] = self.remote_field.limit_choices_to
-        if self.remote_field.related_name is not None:
-            kwargs['related_name'] = self.remote_field.related_name
-        if self.remote_field.related_query_name is not None:
-            kwargs['related_query_name'] = self.remote_field.related_query_name
+        if self._limit_choices_to:
+            kwargs['limit_choices_to'] = self._limit_choices_to
+        if self._related_name is not None:
+            kwargs['related_name'] = self._related_name
+        if self._related_query_name is not None:
+            kwargs['related_query_name'] = self._related_query_name
         return name, path, args, kwargs
 
     def get_forward_related_filter(self, obj):
@@ -471,7 +483,13 @@ class ForeignObject(RelatedField):
                 on_delete=on_delete,
             )
 
-        super().__init__(rel=rel, **kwargs)
+        super().__init__(
+            rel=rel,
+            related_name=related_name,
+            related_query_name=related_query_name,
+            limit_choices_to=limit_choices_to,
+            **kwargs,
+        )
 
         self.from_fields = from_fields
         self.to_fields = to_fields
@@ -825,6 +843,9 @@ class ForeignKey(ForeignObject):
         super().__init__(
             to,
             on_delete,
+            related_name=related_name,
+            related_query_name=related_query_name,
+            limit_choices_to=limit_choices_to,
             from_fields=[RECURSIVE_RELATIONSHIP_CONSTANT],
             to_fields=[to_field],
             **kwargs,
@@ -1174,7 +1195,12 @@ class ManyToManyField(RelatedField):
         )
         self.has_null_arg = 'null' in kwargs
 
-        super().__init__(**kwargs)
+        super().__init__(
+            related_name=related_name,
+            related_query_name=related_query_name,
+            limit_choices_to=limit_choices_to,
+            **kwargs,
+        )
 
         self.db_table = db_table
         self.swappable = swappable
diff --git a/docs/releases/4.0.txt b/docs/releases/4.0.txt
index 831bb9b854..eecbc9e4d8 100644
--- a/docs/releases/4.0.txt
+++ b/docs/releases/4.0.txt
@@ -387,6 +387,18 @@ custom middleware::
 
 .. _Content-Security-Policy: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
 
+Migrations autodetector changes
+-------------------------------
+
+The migrations autodetector now uses model states instead of model classes.
+Also, migration operations for ``ForeignKey`` and ``ManyToManyField`` fields no
+longer specify attributes which were not passed to the fields during
+initialization.
+
+As a side-effect, running ``makemigrations`` might generate no-op
+``AlterField`` operations for ``ManyToManyField`` and ``ForeignKey`` fields in
+some cases.
+
 Miscellaneous
 -------------
 
@@ -422,10 +434,6 @@ Miscellaneous
 * Tests that fail to load, for example due to syntax errors, now always match
   when using :option:`test --tag`.
 
-* The migrations autodetector now uses model states instead of model classes.
-  As a side-effect ``makemigrations`` might generate no-op ``AlterField``
-  operations for ``ForeignKey`` fields in some cases.
-
 * The undocumented ``django.contrib.admin.utils.lookup_needs_distinct()``
   function is renamed to ``lookup_spawns_duplicates()``.
 
diff --git a/tests/field_deconstruction/tests.py b/tests/field_deconstruction/tests.py
index b746e46458..846f6d3ed7 100644
--- a/tests/field_deconstruction/tests.py
+++ b/tests/field_deconstruction/tests.py
@@ -432,6 +432,34 @@ class FieldDeconstructionTests(SimpleTestCase):
         self.assertEqual(kwargs, {"to": "auth.Permission"})
         self.assertEqual(kwargs['to'].setting_name, "AUTH_USER_MODEL")
 
+    def test_many_to_many_field_related_name(self):
+        class MyModel(models.Model):
+            flag = models.BooleanField(default=True)
+            m2m = models.ManyToManyField('self')
+            m2m_related_name = models.ManyToManyField(
+                'self',
+                related_name='custom_name',
+                related_query_name='custom_query_name',
+                limit_choices_to={'flag': True},
+            )
+
+        name, path, args, kwargs = MyModel.m2m.field.deconstruct()
+        self.assertEqual(path, 'django.db.models.ManyToManyField')
+        self.assertEqual(args, [])
+        # deconstruct() should not include attributes which were not passed to
+        # the field during initialization.
+        self.assertEqual(kwargs, {'to': 'field_deconstruction.MyModel'})
+        # Passed attributes.
+        name, path, args, kwargs = MyModel.m2m_related_name.field.deconstruct()
+        self.assertEqual(path, 'django.db.models.ManyToManyField')
+        self.assertEqual(args, [])
+        self.assertEqual(kwargs, {
+            'to': 'field_deconstruction.MyModel',
+            'related_name': 'custom_name',
+            'related_query_name': 'custom_query_name',
+            'limit_choices_to': {'flag': True},
+        })
+
     def test_positive_integer_field(self):
         field = models.PositiveIntegerField()
         name, path, args, kwargs = field.deconstruct()
diff --git a/tests/schema/fields.py b/tests/schema/fields.py
index e4b62eab39..aaba202364 100644
--- a/tests/schema/fields.py
+++ b/tests/schema/fields.py
@@ -34,7 +34,12 @@ class CustomManyToManyField(RelatedField):
         self.db_table = db_table
         if kwargs['rel'].through is not None:
             assert self.db_table is None, "Cannot specify a db_table if an intermediary model is used."
-        super().__init__(**kwargs)
+        super().__init__(
+            related_name=related_name,
+            related_query_name=related_query_name,
+            limit_choices_to=limit_choices_to,
+            **kwargs,
+        )
 
     def contribute_to_class(self, cls, name, **kwargs):
         if self.remote_field.symmetrical and (