Stop Django from creating migrations if the list of choices of a field changes

Question

I have a django core app called \"foocore\".

There are several optional pluging-like apps. For example \"superfoo\".

In my case every plugin adds a new choice in

Answer 1

I had a similar problem with a custom field that I made for a Django 1.6 project that had the same general structure. I came to the following solution which works alright:

class ActivePluginMeta(ModelBase):
    def __new__(cls, name, bases, attrs):
        # Override choices attr
        cls = models.base.ModelBase.__new__(cls, name, bases, attrs)
        setattr(cls._meta.get_field('plugin_name'), 'choices', cls.plugin_name_choices)
        return cls

class ActivePlugin(models.Model, metaclass=ActivePluginMeta):
    plugin_name_choices = get_active_plugins()
    plugin_name = models.CharField(max_length=32, choices=[])

That is for python 3, for python 2 you have to specify the metaclass as follows:

class ActivePlugin(models.Model):
    __metaclass__ = ActivePluginMeta

    plugin_name_choices = get_active_plugins()
    plugin_name = models.CharField(max_length=32, choices=[])

Answer 2

See this bug report and discussion for more info: https://code.djangoproject.com/ticket/22837

The proposed solution was to use a callable as the argument for choices, but it appears this has not been executed for fields but for forms only.

If you really need dynamic choices than a ForeignKey is the best solution.

An alternative solution can be to add the requirement through a custom clean method for the field and/or creating a custom form. Form fields do support callable choices.

See this answer for more info: https://stackoverflow.com/a/33514551/54017