API to customize the list of TYPE_MAPPING

I use sqlalchemy_utils which provide ChoiceType field (and many others).

I’m able to create a new Marshmallow field (Field) to handle this new field with proper _serialize/_deserialize functions but instead to override the attributes one by one in each schema I defined I want to update the list type_mapping in ModelConverter.

I didn’t find how to access it properly, ModelConverter accepts schema_cls attribute at init https://github.com/marshmallow-code/marshmallow-sqlalchemy/blob/dev/marshmallow_sqlalchemy/convert.py#L76 but I’m not able to figure out how to use it properly with all these meta classes 😉

So for now I rely on a monkey patch:

ModelConverter.SQLA_TYPE_MAPPING.update({
    ChoiceType: ChoiceTypeSchema
})

PS: I use flask-marshmallow in my app.

[ThiefMaster]

I don’t think it makes sense to specify a custom converter via Meta if you have a custom SQLAlchemy type that’s used everywhere in your application. There should be a clean/documented way to globally register a new type.

[sloria]

I’m considering making the converter class a class member of the schema rather than class Meta option, i.e.

class SQLAlchemySchema(...):
    Converter = ModelConverter

This could simplify overriding converter methods and attributes, incl. the type mapping.

class MyBaseSchema(SQLAlchemySchema):
    class Converter(SQLAlchemySchema.Converter):
        SQLA_TYPE_MAPPING = {
            **SQLAlchemySchema.Converter.SQLA_TYPE_MAPPING,
            datetime.datetime: UnixTimeStampField,
        }

Thoughts?