invalid code is generated when mixing lists of type and lists of schema using anyOf

[jktr]

Hi! I'm trying to generate a client for an API that returns a list of items, and am seeing invalid code being generated.

The returned items are either all strings or all instances of a specific BaseModel ("Foo"), depending on the value of a query parameter. The API is implemented in FastAPI using response_model = list[str] | list[Foo], which results in an openapi spec that uses anyOf for two arrays, one of type string and the other one referencing the Foo schema.

Trying to run openapi-python-generator on this spec generates the following invalid code, which fails at the black step during compilation.

return [Foo],List[str](**item) for item in body]

I'm using openapi-python-generator v2.1.2, installed via uv into a venv.

To reproduce, run openapi-python-generator openapi.json foo --formatter none using the (minimal) openapi.json below and examine the generated foo/services/default_service.py (also below).

`openapi.json`

{
  "openapi": "3.1.0",
  "info": {
    "title": "FastAPI",
    "version": "0.1.0"
  },
  "paths": {
    "/foo": {
      "get": {
        "tags": [],
        "summary": "Foo",
        "description": "Foo",
        "operationId": "foo",
        "parameters": [],
        "responses": {
          "200": {
            "description": "Successful Response",
            "content": {
              "application/json": {
                "schema": {
                  "anyOf": [
                    {
                      "type": "array",
                      "items": {
                        "$ref": "#/components/schemas/Foo"
                      }
                    },
                    {
                      "type": "array",
                      "items": {
                        "type": "string",
                      }
                    }
                  ],
                  "title": "Foo"
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "Foo": {
        "properties": {
          "foo": {
            "type": "string",
            "title": "Foo"
          }
        },
        "type": "object",
        "required": [
          "foo"
        ],
        "title": "Foo",
        "description": "Foo"
      }
    }
  }
}

malformed `return` statement at `foo/services/default_service.py`

from typing import *
import httpx


from ..models import *
from ..api_config import APIConfig, HTTPException

def foo(api_config_override : Optional[APIConfig] = None) -> Union[List[Foo],List[str]]:
    api_config = api_config_override if api_config_override else APIConfig()

    base_path = api_config.base_path
    path = f'/foo'
    headers = {
        'Content-Type': 'application/json',
        'Accept': 'application/json',
        'Authorization': f'Bearer { api_config.get_access_token() }',
        
    }
    query_params : Dict[str,Any] = {
        }

    query_params = {key:value for (key,value) in query_params.items() if value is not None}

    with httpx.Client(base_url=base_path, verify=api_config.verify) as client:
        response = client.request(
            'get',
        httpx.URL(path),
        headers=headers,
        params=query_params,
            )

    if response.status_code != 200:
        raise HTTPException(response.status_code, f'foo failed with status code: {response.status_code}')
    else:
                body = None if 200 == 204 else response.json()

    return [Foo],List[str](**item) for item in body]