'ManyToManyField' object has no attribute 'm2m_reverse_field_name' - django

Question

I'm trying to run a migration for my Django project, but I'm getting the error:
AttributeError: 'ManyToManyField' object has no attribute 'm2m_reverse_field_name'
I when I ran make migrations on all my apps, I didn't get any errors. It's only when I try to actually migrate. I can't tell from the traceback information which model is creating the problem, or even which app. I've looked at my models, and I don't see anything that pops out at me.
Here is the stack trace:
Operations to perform:
Apply all migrations: admin, sessions, case_manager, file_manager, auth, contenttypes, tasks, people_and_property
Running migrations:
Rendering model states... DONE
Applying file_manager.0006_auto_20160109_1536...Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/core/management/__init__.py", line 350, in execute_from_command_line
utility.execute()
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/core/management/__init__.py", line 342, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/core/management/base.py", line 348, in run_from_argv
self.execute(*args, **cmd_options)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/core/management/base.py", line 399, in execute
output = self.handle(*args, **options)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/core/management/commands/migrate.py", line 200, in handle
executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/db/migrations/executor.py", line 92, in migrate
self._migrate_all_forwards(plan, full_plan, fake=fake, fake_initial=fake_initial)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/db/migrations/executor.py", line 121, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/db/migrations/executor.py", line 198, in apply_migration
state = migration.apply(state, schema_editor)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/db/migrations/migration.py", line 123, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/db/migrations/operations/fields.py", line 201, in database_forwards
schema_editor.alter_field(from_model, from_field, to_field)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/db/backends/base/schema.py", line 467, in alter_field
return self._alter_many_to_many(model, old_field, new_field, strict)
File "/home/mint/Python_Projects/venv/lib/python3.4/site-packages/django/db/backends/sqlite3/schema.py", line 274, in _alter_many_to_many
old_field.remote_field.through._meta.get_field(old_field.m2m_reverse_field_name()),
AttributeError: 'ManyToManyField' object has no attribute 'm2m_reverse_field_name'
How do I figure out which model is the problem? What should I look for?

Answer 1

You have to make sure that the model you are creating the 'ManyToManyField' is already created in the database.
You can do that by adding as a dependency the migration where the model is created to your migration in which you alter the field:
Scenario 1: You alter the field to 'ManyToManyField' with a model from other app
class Migration(migrations.Migration):
dependencies = [
..........
('[app]', '__first__'),
]
operations = [
.........
]
Scenario 2: You create a 'ManyToManyField' and the model you are referring to is in the same file:
class Migration(migrations.Migration):
dependencies = [
..........
]
operations = [
.........
# Make sure the model you are making the reference with is before the ManyToManyField
migrations.CreateModel(...) ,
migrations.AlterField/CreateField(...)
]

Answer 2

I ran into the same problem, but I don’t know if for the same reasons. Luckily I don’t have any important data in the system, so I just changed the migration as follows – but note that this deletes all data in these columns!
Before:
operations = [
migrations.AlterField(
model_name='resource',
name='authors',
field=models.ManyToManyField(related_name='resources_authored', to='api.Person'),
),
migrations.AlterField(
model_name='resource',
name='editors',
field=models.ManyToManyField(blank=True, related_name='resources_edited', to='api.Person'),
),
]
After:
operations = [
migrations.RemoveField(
model_name='resource',
name='authors',
),
migrations.RemoveField(
model_name='resource',
name='editors',
),
migrations.AddField(
model_name='resource',
name='authors',
field=models.ManyToManyField(related_name='resources_authored', to='api.Person'),
),
migrations.AddField(
model_name='resource',
name='editors',
field=models.ManyToManyField(blank=True, related_name='resources_edited', to='api.Person'),
),
]
While the altering failed for mysterious reasons, removing and recreating the fields worked.

Answer 3

One of the reason might be your api.Person model migrations might not have run before the one in which it is referenced(in your example it is file_manager.0006_auto_20160109_1536). So make sure api.Person migrations are run before, by adding them in the dependencies of file_manager.0006_auto_20160109_1536.

Answer 4

I had the same problem when I tried to rename a table which was referenced with a many to many fields.
I resolved it this way:
- dumped the manytomany relationship data into a file
- removed the manytomany field and migrated
- renamed the table and migrated
- added the manytomany field back and migrated and loaded the relationships from the dump

Answer 5

I also had the same problem, but the way that I fixed it, is the following steps:
Nota: You will lose data from that ManyToManyField
python manage.py makemigrations app_name
python manage.py migrate app_name --fake
Don't forget the --fake
After that.
I removed (or just comment the line) the ManyToMany field, and then makemigrations app_name, migrate app_name.
At this step you have this column from your database cleared, what you need to do now is to re add the ManyToManyField, so when you makemigrations app_name & migrate app_name again.
You server can run perfectly
It's not the best, but it worked for me.
hope it will help !

Answer 6

My problem came with changing a field from a choices field to a manytomanyfield.
If you do this and keep the same name, then you'll have issues.
I followed Denis Drescher:
Basically go through your migration files and check what django is doing with these fields.
If django is doing migrations.AlterField for the field which was a choices field and is now a manytomanyfield, change it to
migrations.RemoveField and then Migrations.AddField

Answer 7

I had no meaningful data as yet, so I deleted the database(db.sqlite3) and all migrations(0001,0002 etc)

Answer 8

Simply check if you renamed model-related attributes or anthing related to the model in the admin before you drop the db.
Actually it worked for me.