forms.SchemaField.to_python(): check if value already has a target type

[alexey-sveshnikov]

Hi Savva!

Thank you for the great library! I enjoy using it a lot.

This is a small fix to a problem I encountered after upgrading to v2. I think the patch is pretty much self-explanatory, except for the case which is triggered the bug. It was in a django-constance custom fields config:

CONSTANCE_ADDITIONAL_FIELDS = {
    'my_field_type': [
        'django_pydantic_field.v2.forms.SchemaField', {
            'schema': MyModelName,
        }
    ]
}

CONSTANCE_CONFIG = {
    'MY_FIELD': ({}, '...', 'my_field_type'),
}

[surenkov]

Hi @alexey-sveshnikov, thanks for bringing this up!

I could imagine how this can be a problem with the form, but this particular case is a bit elusive for me -- I haven't had any setup with django-constance, so may I kindly ask you a bit of the detail, like stack trace for example, for historical reasons, as it may be useful for django-pydantic-field users.

Another point that I want to put into consideration, is that it's not always the case that validation schema is pydantic.BaseModel. The field can accept arbitrary annotation as long as it is acceptable by pydantic itself, and checking against isinstance(..., BaseModel) may not solve the issue entirely.
Maybe slightly reversing the condition here, and perform the parsing only if the incoming data is a string which is not a JSONString, otherwise trying to adapt the data with adapter.validate_python could cover the issue better, but that needs to be tested against several cases.

[surenkov]

@alexey-sveshnikov based on the assumptions above, I prepared this PR to your base branch.

These changes are published to PyPI under 0.3.2b1 pre-release -- I would be glad if you can try them against your configuration to test if that would work...

[alexey-sveshnikov]

Thank you.

I've added bytes to the condition as well.

stack trace for example, for historical reasons, as it may be useful for django-pydantic-field users.

I actually have no stack traces. The exception I got was ValidationError and it has been handled like normal validation error (Schema didn't match for MyModel)

[alexey-sveshnikov]

0.3.2b1 works fine with django-constance!

[surenkov]

Great, thank you! I'll prepare the next patch for PyPI.