Custom directives & field visibility - FastQL

Custom directives

@Directive registers a directive definition; its arguments are derived from the class’s type hints. Apply it to types, fields, or arguments with AppliedDirective, whose locations and argument types are validated at build time and rendered in the SDL.

from fastql import Argument, Directive, Field, Type
from fastql.types import AppliedDirective


@Directive(locations=["FIELD_DEFINITION", "OBJECT"], description="tag things")
class tag:
    name: str


@Type(directives=[AppliedDirective("tag", {"name": "obj"})])
class Widget:
    id: int

    @Field(directives=[AppliedDirective("tag", {"name": "fieldlevel"})])
    def label(self) -> str:
        return "w"

Field visibility

Field(private=True) keeps a Python attribute off the GraphQL schema (still readable by resolvers); Field(external=True) marks a field as federation-@external.

@Type
class User:
    handle: str
    secret: str = Field(private=True)        # excluded from the schema

Enum customization

enum_value sets a member’s GraphQL name, description, or deprecation.

from fastql import Enum, enum_value


@Enum
class Color:
    RED = "red"
    GREEN = enum_value("green", description="leafy", deprecation_reason="use RED")
    BLUE = enum_value("blue", name="AZURE")  # exposed as AZURE