@validates accepts multiple field names

[dharani7998]

Fix for #1960

[sloria]

apologies for the long delay on this. i hesitated initially because i had the same concern as @deckar01 about this being a breaking change. now that we're closing to releasing the next major, i think this is one that we can get merged. i'll update this when i have some time

[sloria]

should validator methods receive field_name?

from marshmallow import Schema, fields, validates, ValidationError

class UserSchema(Schema):
    name = fields.Str(required=True)
    nickname = fields.Str(required=True)

    @validates("name", "nickname")
    def validate_names(self, value: str, field_name: str) -> str:
        if len(value) < 3:
            raise ValidationError(f"{field_name} too short")
        return value

[sloria]

looks like SQLAlchemy does pass a key argument: https://docs.sqlalchemy.org/en/20/orm/mapped_attributes.html#simple-validators

from sqlalchemy.orm import validates


class EmailAddress(Base):
    __tablename__ = "address"

    id = mapped_column(Integer, primary_key=True)
    email = mapped_column(String)

    @validates("email")
    def validate_email(self, key, address):
        if "@" not in address:
            raise ValueError("failed simple email validation")
        return address

[sloria]

Updated to pass data_key as a keyword argument to decorated methods. Would like one review on this since it's a breaking change