Improve Model flexibility by allowing a custom Options class

[Chris Wilson]

For example, if I want to specify that my model has custom permissions, to be able to use them in the admin, I can't subclass Options to add or change the get_*_permission methods, because ModelBase.__new__ does this:

new_class.add_to_class('_meta', Options(meta, **kwargs))

I think it would be great to allow specifying a different Options class in the model's Meta class:

class MyModelOptions(Options):
    def get_view_permission(self):
        return 'view_%s' % self.object_name.lower()

class MyModel(Model):
    class Meta:
        options_class = MyModelOptions

I think the code change would be quite simple:

options_class = getattr(meta, 'options_class', Options)
new_class.add_to_class('_meta', options_class(meta, **kwargs))

Acceptable?

[Anssi Kääriäinen]

The big problem is that the whole Options (Model._meta) is private API. It is often used, but it is still private API. So, before the API of the Options is public I don't see a point in the meta option of overriding the state class. For this reason wontfix.

I do see that one could do nice things with custom Options class. I am not denying that. But we need some API for Options first. If you absolutely need to override the options class, you can use custom metaclass, and then from the custom metaclass use the custom Options class.

Refactoring the code in a way that you have a nice hook for this is IMHO acceptable. Basically, the getattr(meta, 'options_class', Options) could be turned to self.get_options_class(). Override get_options_class() and you got your custom Options class. This all would be private API, but you could use it if you absolutely need.

[Chris Wilson]

Sorry, but I don't understand why adding this code:

options_class = self.get_options_class()
...
def get_options_class(self):
    return Options

is better than this:

options_class = getattr(meta, 'options_class', Options)

Please can you enlighten me?

[Anssi Kääriäinen]

Maybe you are right. But AFAICS the meta options are public. The hook would be non-public. Maybe this is over pedantic on my part, but there is currently zero non-public meta options.