id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
34820	Migrations crashes when changing ForeignObject properties.	puc_dong	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
"	Bug	closed	Database layer (models, ORM)	4.2	Normal	fixed			Ready for checkin	1	0	0	0	0	0