Bug: OpenAPI spec blank response schema when using Response object

[pavdwest]

Description

See example below - using the Scalar docs the schema for the get_items endpoint is blank (just says "No Body"). Ideally the schema would be populated exactly as if the response wasn't wrapped in a "Response" object, i.e. it should just use the type hinting info List[Item].

URL to code causing the issue

http://127.0.0.1:8000/schema

MCVE

from dataclasses import dataclass
from typing import List

from litestar import Litestar, get, Response
from litestar.openapi import OpenAPIConfig
from litestar.openapi.plugins import ScalarRenderPlugin
from litestar.dto import DataclassDTO, DTOConfig


@dataclass
class Item:
    id: int
    name: str
    secret: str


class ItemReadDTO(DataclassDTO[Item]):
    config = DTOConfig(exclude=["secret"])


@get("/get_items", return_dto=ItemReadDTO)
async def get_items() -> Response[List[Item]]:
    return Response(
        headers={"X-SomeParam": "SomeValue"},
        content=[
            Item(id=1, name="Item 1", secret='123'),
            Item(id=2, name="Item 2", secret='456'),
        ]
    )


@get("/get_items_raw", return_dto=ItemReadDTO)
async def get_items_raw() -> List[Item]:
    return [
        Item(id=1, name="Item 1", secret='123'),
        Item(id=2, name="Item 2", secret='456'),
    ]


app = Litestar(
    route_handlers=[get_items, get_items_raw],
    openapi_config=OpenAPIConfig(
        title="Scalar Issue",
        version="0.1.0",
        render_plugins=[ScalarRenderPlugin()],
    ),
    debug=True,
)

Steps to reproduce

run uvicorn main:app

Screenshots

"![SCREENSHOT_DESCRIPTION](SCREENSHOT_LINK.png)"

Logs

No response

Litestar Version

2.13.0

Platform

• Linux
• Mac
• Windows
• Other (Please specify in the description above)

[provinzkraut]

I think this is a bug with DTOs, not the Response itself

[pavdwest]

@provinzkraut indeed that makes sense.

FYI, the following endpoint (that returns a Response but doesn't specify a return_dto in the route decorator) also has the same issue.

@get("/get_items_nodto")
async def get_items_nodto() -> List[ItemReadDTO]:
    return Response(
        headers={"X-SomeParam": "SomeValue"},
        content=[
            Item(id=1, name="Item 1", secret='123'),
            Item(id=2, name="Item 2", secret='456'),
        ]
    )

However, using a response with a non-dto works correctly, e.g.

@get("/get_items_nodto")
async def get_items_nodto() -> List[Item]:
    return Response(
        headers={"X-SomeParam": "SomeValue"},
        content=[
            Item(id=1, name="Item 1", secret='123'),
            Item(id=2, name="Item 2", secret='456'),
        ]
    )

[mmev]

I've checked the issue using MCVE and it looks like the issue is still relevant
If no one is working on it, I'd be happy to take this one and work on it

[provinzkraut]

@provinzkraut indeed that makes sense.

FYI, the following endpoint (that returns a Response but doesn't specify a return_dto in the route decorator) also has the same issue.

@get("/get_items_nodto")
async def get_items_nodto() -> List[ItemReadDTO]:
    return Response(
        headers={"X-SomeParam": "SomeValue"},
        content=[
            Item(id=1, name="Item 1", secret='123'),
            Item(id=2, name="Item 2", secret='456'),
        ]
    )

The second part here isn't really a bug, since that's not how DTOs are supposed to work in general. You shouldn't return a DTO type directly. You always annotate as the actual return type, and then use a DTO to specify the transformation steps.

[provinzkraut]

I've checked the issue using MCVE and it looks like the issue is still relevant If no one is working on it, I'd be happy to take this one and work on it

Sure thing!

[github-actions]

A fix for this issue has been released in v2.17.0