Adding auto_now field to model causes migrate exception

[James Addison]

I have a feeling this bug has already been filed, but I couldn't (easily) find it.

It looks like the makemigrations command is failing to import (or use) the datetime module properly. My steps:

• On an existing model, add a DateTimeField with auto_now=True set
• Run makemigrations command
• Run migrate command

Result is an exception, detailed below.

Calling makemigrations:

(project1)jaddison@jamess-air-2:~/projects/project1 (master)$ ./manage.py makemigrations
You are trying to add a non-nullable field 'updated' to contentlink without a default;
we can't do that (the database needs something to populate existing rows).
Please select a fix:
 1) Provide a one-off default now (will be set on all existing rows)
 2) Quit, and let me add a default in models.py
Select an option: 1       
Please enter the default value now, as valid Python
The datetime module is available, so you can do e.g. datetime.date.today()
>>> datetime.datetime.now()
Migrations for 'content':
  0003_contentlink_updated.py:
    - Add field updated to contentlink

Calling migrate:

(project1)jaddison@jamess-air-2:~/projects/project1 (master)$ ./manage.py migrate
Traceback (most recent call last):
  File "./manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/jaddison/.virtualenvs/project1/lib/python2.7/site-packages/django/core/management/__init__.py", line 427, in execute_from_command_line
    utility.execute()
  File "/Users/jaddison/.virtualenvs/project1/lib/python2.7/site-packages/django/core/management/__init__.py", line 419, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/jaddison/.virtualenvs/project1/lib/python2.7/site-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/Users/jaddison/.virtualenvs/project1/lib/python2.7/site-packages/django/core/management/base.py", line 337, in execute
    output = self.handle(*args, **options)
  File "/Users/jaddison/.virtualenvs/project1/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 62, in handle
    executor = MigrationExecutor(connection, self.migration_progress_callback)
  File "/Users/jaddison/.virtualenvs/project1/lib/python2.7/site-packages/django/db/migrations/executor.py", line 14, in __init__
    self.loader = MigrationLoader(self.connection)
  File "/Users/jaddison/.virtualenvs/project1/lib/python2.7/site-packages/django/db/migrations/loader.py", line 48, in __init__
    self.build_graph()
  File "/Users/jaddison/.virtualenvs/project1/lib/python2.7/site-packages/django/db/migrations/loader.py", line 145, in build_graph
    self.load_disk()
  File "/Users/jaddison/.virtualenvs/project1/lib/python2.7/site-packages/django/db/migrations/loader.py", line 103, in load_disk
    migration_module = import_module("%s.%s" % (module_name, migration_name))
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/Users/jaddison/projects/project1/content/migrations/0003_contentlink_updated.py", line 6, in <module>
    class Migration(migrations.Migration):
  File "/Users/jaddison/projects/project1/content/migrations/0003_contentlink_updated.py", line 16, in Migration
    field=models.DateTimeField(default=datetime(2014, 4, 25, 4, 32, 56, 89929), auto_now=True),
TypeError: 'module' object is not callable

The contents of the generated migration 0003_contentlink_updated.py:

# encoding: utf8
from django.db import models, migrations
import datetime


class Migration(migrations.Migration):

    dependencies = [
        ('content', '0002_contentlink_body'),
    ]

    operations = [
        migrations.AddField(
            model_name='contentlink',
            name='updated',
            field=models.DateTimeField(default=datetime(2014, 4, 25, 4, 32, 56, 89929), auto_now=True),
            preserve_default=False,
        ),
    ]

Note that it should be default=datetime.datetime(2014, 4, 25, 4, 32, 56, 89929) instead.

[James Addison]

As an additional note, would it not be wise to use timezone.now() if time zone support is active? (see ​https://docs.djangoproject.com/en/1.7/topics/i18n/timezones/#naive-and-aware-datetime-objects)

After fixing the migration to use datetime.datetime(...) in the original bug report, the migration runs fine, however I get this warning:

  ...
  Applying content.0003_contentlink_updated.../Users/jaddison/.virtualenvs/project1/lib/python2.7/site-packages/django/db/backends/sqlite3/base.py:63: RuntimeWarning: SQLite received a naive datetime (2014-04-25 04:32:56.089929) while time zone support is active.
  RuntimeWarning)

[loic84]

I believe this was fixed with 074d3183d92cd5ed5da8f51e7048b12a96f55e0a, could you try the master branch?

[Tim Graham]

I confirmed this has been fixed. I am not sure about the issue of using timezone.now() but it should be a separate ticket.

[Tim Graham]

You can read about the state of time zones in migrations #21954 (tldr; they're not supported right now).