Migrations crashes when changing ForeignObject properties.

[puc_dong]

Execute migrate to report an error

If the models.ForeignObject attribute is used, changing null or blank to generate a new migration record will result in an error message when executing the migrate again

File "/Users/donghao/test/test_migations/manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/__init__.py", line 442, in execute_from_command_line
    utility.execute()
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/__init__.py", line 436, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/base.py", line 412, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/base.py", line 458, in execute
    output = self.handle(*args, **options)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/base.py", line 106, in wrapper
    res = handle_func(*args, **kwargs)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/commands/migrate.py", line 356, in handle
    post_migrate_state = executor.migrate(
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/migrations/executor.py", line 135, in migrate
    state = self._migrate_all_forwards(
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/migrations/executor.py", line 167, in _migrate_all_forwards
    state = self.apply_migration(
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/migrations/executor.py", line 252, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/migrations/migration.py", line 132, in apply
    operation.database_forwards(
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/migrations/operations/fields.py", line 235, in database_forwards
    schema_editor.alter_field(from_model, from_field, to_field)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/backends/base/schema.py", line 785, in alter_field
    if not self._field_should_be_altered(old_field, new_field):
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/backends/base/schema.py", line 1530, in _field_should_be_altered
    return self.quote_name(old_field.column) != self.quote_name(
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/backends/base/schema.py", line 204, in quote_name
    return self.connection.ops.quote_name(name)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/backends/mysql/operations.py", line 184, in quote_name
    if name.startswith("`") and name.endswith("`"):
AttributeError: 'NoneType' object has no attribute 'startswith'

models:

# app1:
class Model1(models.Model):
    name = models.CharField(max_length=50)

# app2:
class Model2(models.Model):
    name = models.CharField(max_length=100, db_index=True)
    clu_id = models.BigIntegerField()
    scenes = models.ForeignObject(Model1,
                                  from_fields=['clu_id'],
                                  to_fields=['id'],
                                  null=True,
                                  related_name='model2_config',
                                  on_delete=models.DO_NOTHING)

Successfully executed makemigrations&migrate for the first time. When I add blank=True to the scenes field of Model2, and then execute makemigrations and migrate to report an error
All migration files：
app1.0001_initial.py

class Migration(migrations.Migration):

    initial = True

    dependencies = [
    ]

    operations = [
        migrations.CreateModel(
            name='Model1',
            fields=[
                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('name', models.CharField(max_length=50)),
            ],
        ),
    ]

app2.0001_initial.py

class Migration(migrations.Migration):

    initial = True

    dependencies = [
        ('app_1', '0001_initial'),
    ]

    operations = [
        migrations.CreateModel(
            name='Model2',
            fields=[
                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('name', models.CharField(db_index=True, max_length=100)),
                ('clu_id', models.BigIntegerField()),
                ('scenes', models.ForeignObject(from_fields=['clu_id'], null=True, on_delete=django.db.models.deletion.DO_NOTHING, related_name='model2_config', to='app_1.model1', to_fields=['id'])),
            ],
        ),
    ]

app2.0002_alter_model2_scenes.py

class Migration(migrations.Migration):

    dependencies = [
        ('app_1', '0001_initial'),
        ('app_2', '0001_initial'),
    ]

    operations = [
        migrations.AlterField(
            model_name='model2',
            name='scenes',
            field=models.ForeignObject(blank=True, from_fields=('clu_id',), null=True, on_delete=django.db.models.deletion.DO_NOTHING, related_name='model2_config', to='app_1.model1', to_fields=('id',)),
        ),
    ]

FIX: ​https://github.com/django/django/pull/17235

[Mariusz Felisiak]

I'm not sure how to you reach a field without a column in migrations. I don't think you've explained the issue in enough detail to confirm a bug in Django, can you provide a sample project or test case that reproduces the issue?

[puc_dong]

Replying to Mariusz Felisiak:

I'm not sure how to you reach a field without a column in migrations. I don't think you've explained the issue in enough detail to confirm a bug in Django, can you provide a sample project or test case that reproduces the issue?

I submitted my case code and process

[puc_dong]

(simpleui) ☁  test_migations  python manage.py makemigrations 
System check identified some issues:

WARNINGS:
app_1.Model1: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
        HINT: Configure the DEFAULT_AUTO_FIELD setting or the App1Config.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
app_2.Model2: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
        HINT: Configure the DEFAULT_AUTO_FIELD setting or the App2Config.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
Migrations for 'app_1':
  app_1/migrations/0001_initial.py
    - Create model Model1
Migrations for 'app_2':
  app_2/migrations/0001_initial.py
    - Create model Model2
(simpleui) ☁  test_migations  python manage.py migrate        
System check identified some issues:

WARNINGS:
app_1.Model1: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
        HINT: Configure the DEFAULT_AUTO_FIELD setting or the App1Config.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
app_2.Model2: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
        HINT: Configure the DEFAULT_AUTO_FIELD setting or the App2Config.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
Operations to perform:
  Apply all migrations: admin, app_1, app_2, auth, contenttypes, sessions
Running migrations:
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  Applying admin.0002_logentry_remove_auto_add... OK
  Applying admin.0003_logentry_add_action_flag_choices... OK
  Applying app_1.0001_initial... OK
  Applying app_2.0001_initial... OK
  Applying contenttypes.0002_remove_content_type_name... OK
  Applying auth.0002_alter_permission_name_max_length... OK
  Applying auth.0003_alter_user_email_max_length... OK
  Applying auth.0004_alter_user_username_opts... OK
  Applying auth.0005_alter_user_last_login_null... OK
  Applying auth.0006_require_contenttypes_0002... OK
  Applying auth.0007_alter_validators_add_error_messages... OK
  Applying auth.0008_alter_user_username_max_length... OK
  Applying auth.0009_alter_user_last_name_max_length... OK
  Applying auth.0010_alter_group_name_max_length... OK
  Applying auth.0011_update_proxy_permissions... OK
  Applying auth.0012_alter_user_first_name_max_length... OK
  Applying sessions.0001_initial... OK

**Add blank=True to the scenes field of Model2**

(simpleui) ☁  test_migations  python manage.py makemigrations 
System check identified some issues:

WARNINGS:
app_1.Model1: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
        HINT: Configure the DEFAULT_AUTO_FIELD setting or the App1Config.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
app_2.Model2: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
        HINT: Configure the DEFAULT_AUTO_FIELD setting or the App2Config.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
Migrations for 'app_2':
  app_2/migrations/0002_alter_model2_scenes.py
    - Alter field scenes on model2

(simpleui) ☁  test_migations  python manage.py migrate        
System check identified some issues:

WARNINGS:
app_1.Model1: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
        HINT: Configure the DEFAULT_AUTO_FIELD setting or the App1Config.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
app_2.Model2: (models.W042) Auto-created primary key used when not defining a primary key type, by default 'django.db.models.AutoField'.
        HINT: Configure the DEFAULT_AUTO_FIELD setting or the App2Config.default_auto_field attribute to point to a subclass of AutoField, e.g. 'django.db.models.BigAutoField'.
Operations to perform:
  Apply all migrations: admin, app_1, app_2, auth, contenttypes, sessions
Running migrations:
  Applying app_2.0002_alter_model2_scenes...Traceback (most recent call last):
  File "/Users/donghao/test/test_migations/manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/__init__.py", line 442, in execute_from_command_line
    utility.execute()
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/__init__.py", line 436, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/base.py", line 412, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/base.py", line 458, in execute
    output = self.handle(*args, **options)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/base.py", line 106, in wrapper
    res = handle_func(*args, **kwargs)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/core/management/commands/migrate.py", line 356, in handle
    post_migrate_state = executor.migrate(
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/migrations/executor.py", line 135, in migrate
    state = self._migrate_all_forwards(
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/migrations/executor.py", line 167, in _migrate_all_forwards
    state = self.apply_migration(
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/migrations/executor.py", line 252, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/migrations/migration.py", line 132, in apply
    operation.database_forwards(
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/migrations/operations/fields.py", line 235, in database_forwards
    schema_editor.alter_field(from_model, from_field, to_field)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/backends/base/schema.py", line 785, in alter_field
    if not self._field_should_be_altered(old_field, new_field):
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/backends/base/schema.py", line 1520, in _field_should_be_altered
    return self.quote_name(old_field.column) != self.quote_name(
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/backends/base/schema.py", line 204, in quote_name
    return self.connection.ops.quote_name(name)
  File "/Users/donghao/.virtualenvs/simpleui/lib/python3.9/site-packages/django/db/backends/mysql/operations.py", line 184, in quote_name
    if name.startswith("`") and name.endswith("`"):
AttributeError: 'NoneType' object has no attribute 'startswith'

[Mariusz Felisiak]

ForeignObject is an abstraction level, not a proper model field. You should use models.ForeignKey. If you're having trouble understanding how Django works, see TicketClosingReasons/UseSupportChannels for ways to get help.

[puc_dong]

Replying to Mariusz Felisiak:

ForeignObject is an abstraction level, not a proper model field. You should use models.ForeignKey. If you're having trouble understanding how Django works, see TicketClosingReasons/UseSupportChannels for ways to get help.

We do not need to create a foreign key, we have used ForeignObject and currently only need to perform queries. Should this field not be generated in the migration record for the first time?

[Mariusz Felisiak]

Replying to puc_dong:

Replying to Mariusz Felisiak:

ForeignObject is an abstraction level, not a proper model field. You should use models.ForeignKey. If you're having trouble understanding how Django works, see TicketClosingReasons/UseSupportChannels for ways to get help.

We do not need to create a foreign key, we have used ForeignObject and currently only need to perform queries. Should this field not be generated in the migration record for the first time?

It seems that you have a niche use case. Trac is not a support channel, you can try to discuss this with folks on the Django Forum.

[Mariusz Felisiak]

After reconsideration I think we should fix this (check out similar report #25128).

[Mariusz Felisiak]

A regression test:

tests/migrations/test_operations.py

@@ -2306 +2306 @@
                 operation.database_forwards(app_label, editor, new_state, project_state)
         self.assertColumnExists(rider_table, "pony_id")
 
+    def test_alter_field_foreignobject_noop(self):
+        app_label = "test_alflfo_noop"
+        project_state = self.set_up_test_model(app_label)
+        project_state = self.apply_operations(
+            app_label,
+            project_state,
+            [
+                migrations.CreateModel(
+                    "Rider",
+                    fields=[
+                        ("pony_id", models.IntegerField()),
+                        (
+                            "pony",
+                            models.ForeignObject(
+                                f"{app_label}.Pony",
+                                models.CASCADE,
+                                from_fields=("pony_id",),
+                                to_fields=("id",),
+                            ),
+                        ),
+                    ],
+                ),
+            ],
+        )
+        operation = migrations.AlterField(
+            "Rider",
+            "pony",
+            models.ForeignObject(
+                f"{app_label}.Pony",
+                models.CASCADE,
+                from_fields=("pony_id",),
+                to_fields=("id",),
+                null=True,
+            ),
+        )
+        new_state = project_state.clone()
+        operation.state_forwards(app_label, new_state)
+        with self.assertNumQueries(0), connection.schema_editor() as editor:
+            operation.database_forwards(app_label, editor, project_state, new_state)
+
     @skipUnlessDBFeature("supports_comments")
     def test_alter_model_table_comment(self):
         app_label = "test_almotaco"

[puc_dong]

Replying to Mariusz Felisiak:

A regression test:

tests/migrations/test_operations.py

@@ -2306 +2306 @@
                 operation.database_forwards(app_label, editor, new_state, project_state)
         self.assertColumnExists(rider_table, "pony_id")
 
+    def test_alter_field_foreignobject_noop(self):
+        app_label = "test_alflfo_noop"
+        project_state = self.set_up_test_model(app_label)
+        project_state = self.apply_operations(
+            app_label,
+            project_state,
+            [
+                migrations.CreateModel(
+                    "Rider",
+                    fields=[
+                        ("pony_id", models.IntegerField()),
+                        (
+                            "pony",
+                            models.ForeignObject(
+                                f"{app_label}.Pony",
+                                models.CASCADE,
+                                from_fields=("pony_id",),
+                                to_fields=("id",),
+                            ),
+                        ),
+                    ],
+                ),
+            ],
+        )
+        operation = migrations.AlterField(
+            "Rider",
+            "pony",
+            models.ForeignObject(
+                f"{app_label}.Pony",
+                models.CASCADE,
+                from_fields=("pony_id",),
+                to_fields=("id",),
+                null=True,
+            ),
+        )
+        new_state = project_state.clone()
+        operation.state_forwards(app_label, new_state)
+        with self.assertNumQueries(0), connection.schema_editor() as editor:
+            operation.database_forwards(app_label, editor, project_state, new_state)
+
     @skipUnlessDBFeature("supports_comments")
     def test_alter_model_table_comment(self):
         app_label = "test_almotaco"

I realized that there will be a default exclude behavior, and there are 6 queries that will be executed in database setup, so I modified the use case, and the 6 queries were not written directly.
This is my modification：​https://github.com/django/django/pull/17240

[Mariusz Felisiak <felisiak.mariusz@…>]

In 71820c9f:

Fixed #34820 -- Fixed migrations crash when changing a ForeignObject field.