Generate Field Based On Data From Another Field

[rgajason]

We have a model that is linked to another with a root validator that checks to ensure the one of the child attributes is prefixed by data from the parent attribute:

def widget_root_validation(cls, values: dict) -> dict:
    owned_by_team = values.get("owned_by_team")
    if not isinstance(owned_by_team, Link):
        name = values.get("name")
        team_short_name = owned_by_team.short_name
        if not name.startswith(f"{team_short_name}-"):
            raise ValidationException("Widget name must start with team short name")


class Team(Document):
    short_name: str


class Widget(Document):
    owned_by_team: Link[Team]
    name: str

    _validate_root = root_validator(allow_reuse=True)(widget_root_validation)

Assuming an instance of Widget is owned by a Team with a short_name of "foo", the name of the widget must be "foo-".

Is this a use case for the PostGenerated() helper:

https://starlite-api.github.io/pydantic-factories/usage/4-defining-factory-fields/#postgenerated

I'm wondering if the model will fail validation before I even get to PostGenerated()...

Is it possible to access the instance attributes during generation? Perhaps I could override get_field_value()...

Thanks in advance for any thoughts.

[rgajason]

Looks like PostGenerated() is working. I thought it would happen after everything else was done, but it looks like it is called immediately when the data for the attribute is being generated. One thing I couldn't figure out was how to get access to the instance of the Faker object that the factory is using. For my use case this is fine, but if I were attempting to seed the Faker that might be a problem.

def add_short_name_prefix(name: str, values: dict[str, Any], *args, **kwargs) -> str:
    team_short_name = values["owned_by_team"].short_name
    random_name = Faker().slug()
    return f"{team_short_name}-{random_name}"


class WidgetFactory(BeanieDocumentFactory):
    __model__ = Widget
    id = Ignore()  # noqa: A003
    revision_id = Ignore()

    owned_by_team = Require()
    name = PostGenerated(add_short_name_prefix)

[Goldziher]

there is a method to get_faker() on the factory. What exactly are you trying to achieve?

[rgajason]

I'm starting to wonder if I'm overthinking this...

I'm trying to generate a value for a factory field that combines data from a linked model/fixture with random data from Faker - bonus if the instance of faker that is used is the same from the factory (to preserve any seeding / etc).

I thought maybe I could pass the factory's Faker instance in the PostGenerated(...) definition but I'm not sure how to access the instance.

[Goldziher]

you cant. You can open a PR to add the instance as an optional kwarg injected. Will require some handling to ensure it doesnt become a breaking change- basically you can inspect and determine what kwargs are defined in the PostGenerated, and inject the instance if its required.