Implement helper method to find module path of value

[Jake Howard]

Finding the module path for where a given class or function is defined is functionality used in a few places across the Django codebase. Whilst in the majority of cases, f"{val.__module__}.{val.__qualname__}" is enough, there are some cases it's not.

As part of #35859, a few more cases of this pattern are being added to the codebase. I think we're now at the [point ​https://en.wikipedia.org/wiki/Rule_of_three_(computer_programming)] where it makes sense to extract this out to a helper function somewhere in django.utils. The implementation in django.migrations.serializer.TypeSerializer seems to be the most robust, however will want some more thorough testing based on different input types.

[Jake Howard]

Probably worth holding off on this ticket until #35859 is merged, so all uses can be covered.

[Natalia Bidart]

Thank you Jake for creating the ticket. Could please enumerate the locations of where this functionality is found?

[shrutisachan08]

Hi, I’m interested in working on this.
From what I understand, the goal is to extract the existing TypeSerializer logic for determining a module path into a reusable helper in django.utils, and ensure it covers edge cases where f"{val.module}.{val.qualname}" isn’t sufficient.
My plan would be:

Review and adapt the current implementation in django.migrations.serializer.TypeSerializer.

Add unit tests for different input types (functions, classes, nested classes, builtins, etc.).

Place the helper in django.utils and update the current usages in the codebase to use it.

Could you confirm if this approach makes sense, and if there’s a preferred name/location for the helper before I start a patch?

[Jake Howard]

That sounds like the right approach to me - thanks for picking this up!