Unable to generate pydantic-core schema for <class 'datetime.datetime'> when using Freezegun

[theadam]

In our unit tests, we sometimes use freezegun to make datetime.now deterministic to test out some specific functionality in some pydantic serializable models. Whenever using freezegun I get this error:

pydantic.errors.PydanticSchemaGenerationError: Unable to generate pydantic-core schema for <class 'datetime.datetime'>. Set `arbitrary_types_allowed=True` in the model_config to ignore this error or implement `__get_pydantic_core_schema__` on your type to fully support it.

I tried patching __get_pydantic_core_schema__ on the FakeDatetime and FakeDate classes in freezegun, but it doesnt seem to help. Has anyone encountered this and found a solution?

[zachaysan]

I've also been hit with this issue. What was the change that caused this error to crop up?

[theadam]

@zachaysan If you are asking about the change we made, we are trying to transition to using pydantic for some model serialization. We are currently using custom serialization. Introducing pydantic is what caused this.

[zachaysan]

Thanks for letting me know @theadam. We were able to work around this issue which you can see here:

Flagsmith/flagsmith#3876

It basically loads the model up before FreezeGun gets involved.

[theadam]

@zachaysan I think this solves it. We are using dataclasses and TypeAdapters, but if I create the TypeAdapter before freezing time things are working! Thank you!

[zachaysan]

Happy to hear that it worked out for you :)

…

On Fri, May 3, 2024 at 10:58 AM Adam Nalisnick ***@***.***> wrote: @zachaysan <https://github.com/zachaysan> I think this solves it. We are using dataclasses and TypeAdapters, but if I create the TypeAdapter before freezing time things are working! Thank you! — Reply to this email directly, view it on GitHub <#9343 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABWL674Z6IFFQZM36ULQQDZAOQYZAVCNFSM6AAAAABG6UKFXOVHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4TGMBWG42DA> . You are receiving this because you were mentioned.Message ID: ***@***.***>