FastAPI 0.103 loses custom class name

test_.py

import typing as t

import pytest
from pydantic import BaseModel
from pydantic.json_schema import GenerateJsonSchema

from fastapi import FastAPI
from fastapi._compat import get_definitions
from fastapi.openapi.constants import REF_TEMPLATE
from fastapi.openapi.utils import get_fields_from_routes

T = t.TypeVar("T")

app = FastAPI()


class Response(BaseModel, t.Generic[T]):
    data: T

    @classmethod
    def model_parametrized_name(cls, params: tuple[type[t.Any], ...]) -> str:
        return "IntWrapper"


@app.get("/", response_model=Response[int])
async def get():
    return {"data": 1}


def test_spec():
    spec = app.openapi()
    actual = set(spec["components"]["schemas"].keys())
    assert "IntWrapper" in actual, actual


def test_internals():
    # duplicated from utils.get_openapi()
    all_fields = get_fields_from_routes(list(app.routes))
    schema_generator = GenerateJsonSchema(ref_template=REF_TEMPLATE)
    field_mapping, definitions = get_definitions(
        fields=all_fields,
        schema_generator=schema_generator,
        model_name_map={},
    )

    assert "IntWrapper" in set(definitions), definitions

It works with pydantic v1:

import typing as t

from pydantic.generics import GenericModel

from fastapi import FastAPI
from tests.utils import needs_pydanticv1

T = t.TypeVar("T")

app = FastAPI()


class Response(GenericModel, t.Generic[T]):
    data: T

    @classmethod
    def __concrete_name__(cls, params: tuple[type[t.Any], ...]) -> str:
        return "IntWrapper"


@app.get("/", response_model=Response[int])
async def get():
    return {"data": 1}


@needs_pydanticv1
def test_spec():
    spec = app.openapi()
    actual = set(spec["components"]["schemas"].keys())
    assert "IntWrapper" in actual, actual