Summary

Right now create_instance can take any **kwargs.

But, mypy has no way of actually checking that id=1, address__id=2 are valid keywords for this call.

It can be caught when executed, sure. But typechecking is much faster than writing code + writing tests + running them.

In Django we have a similar pattern of passing keywords like this to filters. Like: User.objects.filter(id=1, settings__profile="public"). For this we use a custom mypy plugin: https://github.com/typeddjango/django-stubs/blob/c9c729073417d0936cb944ab8585ad236ab30321/mypy_django_plugin/transformers/orm_lookups.py#L10

What it does?

• It checks that simple keyword arguments are indeed the correct ones
• It checks that nested __ ones also exist on the nested model
• It still allows **custom_data unpacking
• It generates an error that can be silenced with type: ignore[custom-code]
• All checks like this can be turned off when custom-code is disabled in mypy checks
• It does not affect anything else
• It slows down type-checking a bit for users who added this plugin
• For users without a plugin - nothing happens
• Pyright and PyCharm are unaffected
• It is better to bundle this plugin, but it can be a 3rd party (really hard to maintain)

Plus, in the future more goodies can be added, included DI proper checking, URL params, etc.
It will require its own set of tests via typing.assert_type and maintaince time. Mypy sometimes break plugin-facing APIs.

I can write this plugin if others are interested :)

Basic Example

No response

Drawbacks and Impact

No response

Unresolved questions

No response