KeyError when creating Pydantic models? about piccolo_api

[dantownsend]

@wmshort I know that Pydantic was recently updated, which might be the cause of the issue.

Have you tried using an explicit model_name with create_pydantic_model? I've encountered an issue before with FastAPI and Pydantic which was solved by this.

create_pydantic_model(SomeTable, model_name="my_unique_model_name")

It's a shot in the dark, but might help.

I'll try and replicate the issue.

[wmshort]

I had the same thought, but in fact I was doing that already on the models, so it couldn't have been causing the problems. I did just see somewhere else that having an Enum of the same name on two models might cause the issue! I do have this on my models, so I'm going to try this change.

No effect. :(

[sinisaos]

@wmshort I can replicate your KeyError problem only if I do not use the explicit model_name with create_pydantic_model. If I use model_name everything is fine. FastAPIWrapper works fine. Both Python3.7 and Python3.8 with latest FastAPI (v0.71.0), Pydantic (v1.9.0) and latest Piccolo. Can you show us your schema from tables so we can try it out?

[dantownsend]

@sinisaos Thanks for taking a look.

I tried updating my apps to the latest FastAPI, and it seems OK. So the bug must be quite subtle.

@wmshort The only other things I can think of at the moment are:

• Make sure model_name matches the variable name. So MyModel = create_pydantic_model(SomeTable, model_name="MyModel").
• Make sure create_pydantic_model is called within the global scope, and not within a function or something.

[sinisaos]

@dantownsend William sent me his schema and the only thing I noticed is that in Python 3.7 (which William uses as seen from the error logs) we MUST use model_name because post and put routes are a problem (they use SomeModelIn and SomeModelOut if we write endpoints by ourselves) . In Python 3.8 we don't have to use model_name and everything work fine. I don't know if it will solve the William problem but I don't see anything else.

[dantownsend]

@sinisaos OK, thanks for checking. If it works for Python 3.8 and above, that's definitely helpful to know.

[wmshort]

Thanks, both. All of these conditions are true already, apart from the Python version. I'll give that a try. Otherwise it's probably some corner case and I'll have to experiment some with model_name. Is there any chance it has to do with nested and some naming clash there?

[dantownsend]

@wmshort Yes, nested could be the cause.

[wmshort]

After a little more experimentation I've narrowed the problem down to two tables that both have two ForeignKey fields referencing the same table. (Though in each case, the referenced table is different). It doesn't appear to be nested per se as certain nested tables that do not have the 'two FKs pointing to the same table' issue work perfectly well. So the problem actually seems to be related to the case of a table like:

class BattleOfTheBands(Table):
band1 = ForeignKey(references=Band)
band2 = ForeignKey(references=Band)

which does not appear to play nice with Pydantic, at least under my configuration. Strange, as I am now using Python 3.8 and latest versions of dependencies, which worked for @sinisaos. I'm stumped!