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
29595	Allow using timedelta in migrations questioner	Bas ten Berge	nobody	"I created a model that contains a `models.duration` field:

{{{

class VoiceMessage(models.Model):
....
 duration = models.DurationField(help_text='Contains the sample duration')
...
}}}

It's not a nullable field, so makemigrations correctly asks me for a default value:

{{{
(env) bastb@bastb-vps:/var/www/brownpapersession/dev/brownpapersession$ python manage.py makemigrations
You are trying to add a non-nullable field 'duration' to voicemessage 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 with a null value for this column)
 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 and django.utils.timezone modules are available, so you can do e.g. timezone.now
Type 'exit' to exit this prompt
>>> datetime.timedelta(seconds=1)
Traceback (most recent call last):
  File ""manage.py"", line 10, in <module>
    execute_from_command_line(sys.argv)
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/core/management/__init__.py"", line 371, in execute_from_command_line
    utility.execute()
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/core/management/__init__.py"", line 365, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/core/management/base.py"", line 288, in run_from_argv
    self.execute(*args, **cmd_options)
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/core/management/base.py"", line 335, in execute
    output = self.handle(*args, **options)
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/core/management/commands/makemigrations.py"", line 159, in handle
    migration_name=self.migration_name,
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/db/migrations/autodetector.py"", line 44, in changes
    changes = self._detect_changes(convert_apps, graph)
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/db/migrations/autodetector.py"", line 183, in _detect_changes
    self.generate_added_fields()
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/db/migrations/autodetector.py"", line 824, in generate_added_fields
    self._generate_added_field(app_label, model_name, field_name)
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/db/migrations/autodetector.py"", line 844, in _generate_added_field
    field.default = self.questioner.ask_not_null_addition(field_name, model_name)
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/db/migrations/questioner.py"", line 158, in ask_not_null_addition
    return self._ask_default()
  File ""/var/www/brownpapersession/dev/env/lib/python3.5/site-packages/django/db/migrations/questioner.py"", line 138, in _ask_default
    return eval(code, {}, {""datetime"": datetime_safe, ""timezone"": timezone})
  File ""<string>"", line 1, in <module>
AttributeError: module 'django.utils.datetime_safe' has no attribute 'timedelta'
}}}

To me, the informative message `The datetime and django.utils.timezone modules are available, so you can do e.g. timezone.now` suggests that the python `datetime` module is available, especially because the Django `timezone` was displayed as `django.utils.timezone`.

I'm working around it by accepting a null and blank value for now. I'm happy to create a PR if needed
"	Bug	closed	Migrations	2.0	Normal	fixed			Accepted	1	0	0	0	0	0