Intro

OpenAPI generators have grom a lot by themselves and despite all comply with base OpenAPI specs, many have implemented extra features that would be good to have when getting the schema from FastAPI.

Example use case:

class Gender(IntEnum):
    male = auto()
    female = auto()
    other = auto()
    not_given = auto()

ta = TypeAdapter(Gender)
ta_schema = ta.json_schema()

# This generates the following
assert ta_schema == {
    "enum": [1, 2, 3, 4],
    "title": "Gender",
    "type": "integer"
}

The inconvenience here comes because OpenAPI specs does not hace naming for IntEnum class attributes and most be created by generators without any naming convention...
TypeScript generated code with openapi-generator-cli would look like this and is completely abstract:

export const Gender= {
    NUMBER_1: 1,
    NUMBER_2: 2,
    NUMBER_3: 3,
    NUMBER_4: 4
} as const;
export type Gender = typeof Gender[keyof typeof Gender];

These generators have implemented extra definitions to provide these attributes naming association. This varies depending on the generator but if we keep on with the one we are using already (openapi-generator-cli) that would be the x-enum-varnames.

With a simple implementation, as intended by pydantic, we could get this done in a blink of an eye.

class CustomJsonSchemaGenerator(GenerateJsonSchema):
    def enum_schema(self, schema: EnumSchema) -> JsonSchemaValue:
        generated_schema = super().enum_schema(schema)
        generated_schema['x-enum-varnames'] = [enum.name for enum in schema['members']]

        return generated_schema

With the output being:

export const Gender= {
    MALE: 1,
    FEMALE: 2,
    OTHER: 3,
    NOT_GIVEN: 4
} as const;
export type Gender = typeof Gender[keyof typeof Gender];

Conclusion

FastAPI already has the interface to make this, it just lacks the parameter of the generator to be used. So, adding that to its implementation would be all what is required to have this feature, as shown in the code changes. The rest of FastAPI-ways for openapi overrideshown in the doc will remain the same and the doc will not require update