Allow adding custom types to _native_to_marshmallow

[lovasoa]

Allow adding custom types to _native_to_marshmallow

[evanfwelch]

I would also find this valuable... a mapping you can can pass to class_schema that gets merged with _native_to_marshmallow.

    if typ in _marshmallow_mapping:
        field_fn = _marshmallow_mapping[typ]
        if inpsect.isfunction(field_fn):
            return field_fn(typ, **metadata)
        else: #assume it's just a marshmallow field
             return field_fn(**metadata)

[alextremblay]

There was an idea introduced in another issue (#23) That I think could work very well here:

from typing import List
from ipaddress import IPv4Address

from marshmallow.fields import Field
from marshmallow_dataclass import dataclass, NewType

class IPField(Field):
    ... # serializes an IPv4Address instance into a str, and deserializes back into an instance

#IP = NewType('IP', str, validate=my_validation_function) 
#This was the suggestion in the other issue

IP = NewType('IP', IPv4Address, marshmallow_field=IPField)

@dataclass
class Company:
    name: str
    ipv4s: List[IP]

The idea is to have a NewType implementation that works the same as typing.NewType, but also stores all the field metadata that we would normally store on a dataclass field, like validation functions and marshmallow_field selections.

Thoughts?

[lovasoa]

The supported way to use custom fields for your type is to add a marshmallow_field key to your field metadata, and make it contain your marshmallow field.

[rakanalh]

I did see it in the documentation. The reason i wanted to not do this is because of what i wrote in a comment in a different issue:
#15 (comment)

[lovasoa]

I just published version 6.1.0rc1 with support for NewType. You can check out the README, the documentation, and try it. If you encounter any issues, or find that something could be improved in the documentation, open an issue. If no one complains, then I'll publish it as 6.1.0 and close this issue.

[lovasoa]

Version 6.1.0 was just released with support for NewType, so I am closing this.
https://pypi.org/project/marshmallow-dataclass/6.1.0/