from sqlmodel import Relationship, SQLModel, Field
from pydantic.main import BaseModel


class SpecialFieldValidator(BaseModel):
    id: int = Field(primary_key=True, index=True)

    def __init_subclass__(cls) -> None:
        # Try to figure out what type the special_field relation has
        print("special_field" in cls.__annotations__)  # False
        print("special_field" in cls.__fields__)  # False
        print("special_field" in cls.__sqlmodel_relationships__)  # True, but no type info via this dict, just a plain RelationshipInfo() instance:
        print(dict(cls.__sqlmodel_relationships__["special_field"].__dict__))  # {'back_populates': None, 'link_model': None, 'sa_relationship': None, 'sa_relationship_args': None, 'sa_relationship_kwargs': None}

        return super().__init_subclass__()

class MyModelA(SQLModel, SpecialFieldValidator, table=True):
    id: int = Field(primary_key=True)
    special_field_id: int = Field(foreign_key="mymodelb.id")
    special_field: "MyModelB" = Relationship()

    def __new__(cls, *args: Any, **kwargs: Any) -> Any:
        new_object = super().__new__(cls, *args, **kwargs)
        new_object.model_fields.update({"special_field": Field(..., description="description of your model property coming from the relationship")})
        new_object.model_rebuild(force=True)
        return new_object

class MyModelB(SQLModel, SpecialFieldValidator, table=True):
    id: int = Field(primary_key=True)
    special_field_id: int = Field(foreign_key="mymodela.id")
    special_field: MyModelA = Relationship()
   
    def __new__(cls, *args: Any, **kwargs: Any) -> Any:
        new_object = super().__new__(cls, *args, **kwargs)
        new_object.model_fields.update({"special_field": Field(..., description="description of your model property coming from the relationship")})
        new_object.model_rebuild(force=True)
        return new_object