give more context to custom schemas

[chenguo]

Kind of a corner case, I have a schema with a custom field that holds a recursive instance of that same schema, and I got blocked on not having access to obj in my custom _jsonschema_type_mapping call

[chenguo]

@fuhrysteve
just checking on the status of this repo, I see another PR was opened mid Jan and hasn't had movement. Is this project still actively maintained?

[fuhrysteve]

@chenguo Thanks for the PR! Yes it this project is still very much actively maintained, though I don't always review PRs right away

[fuhrysteve]

Hmm, the problem with this is that it would break backward compatibility with custom type support as currently documented:

https://github.com/fuhrysteve/marshmallow-jsonschema#custom-type-support

Is there a way we can achieve what your trying to do without breaking backward compatibility?

[chenguo]

hmm yeah, i think a part of the difficulty here is actually the kind of ad-hoc nature of jsonschema_type_mapping, where there's no explicit definition of an interface so we can't just update some base definition like

def _jsonschema_type_mapping(self, json_schema = None, obj = None):
  ...

to make this easily work for everyone.

I think similar to how you're using reflection to check if that _jsonschema_type_mapping even exists, I can use inspect to count the number of arguments and only pass the context in if the argument count supports it. This would preserve existing behavior but does make this interface a bit more loosey than it already is.

I think I'm ok with that. You could argue a proper solution requires a revamp of how this functionality is supported anyhow, so the best we can do atm is just to bolt more on to what was bolted on.

I'll make an update, and also be sure to update the README this time.

[chenguo]

Ok, updated to not break existing interfaces, and added a README section to detail when this particular corner case is hit. Thanks for the feedback, lmk what else you need.