Bug: failure to reflect constraints in autogenerated OpenAPI spec

[umarbutler]

Description

Adding a gt constraint to an int with either msgpec.Meta or litestar.params.Body() fails to have that greater than constraint reflected in the autogenerated OpenAPI spec.

Here is the MRE:

from typing import Annotated

import msgspec

from litestar import get, Request, Litestar
from litestar.params import Body


class Resp(msgspec.Struct):
    foo: Annotated[int, msgspec.Meta(gt=0), Body(gt=0)]

Resp = Annotated[Resp, Body(description="A response object.")]

@get("/")
async def home() -> Resp:
    return Resp(1)

@get(path=["/openapi.json"], include_in_schema=False, sync_to_thread=True)
def get_openapi(request: Request) -> dict:
    schema = request.app.openapi_schema

    return schema.to_schema()

app = Litestar(
    [home, get_openapi],
)

if __name__ == "__main__":
    import uvicorn

    try:
        uvicorn.run(
            app = "_mre:app",
            host = "localhost",
            port = 2020,
            reload = True,
        )
    
    except Exception:
        uvicorn.run(
            app = app,
            host = "localhost",
            port = 2020,
        )

Here is the autogenerated OpenAPI spec:

{
  "info": {
    "title": "Litestar API",
    "version": "1.0.0"
  },
  "openapi": "3.1.0",
  "servers": [
    {
      "url": "/"
    }
  ],
  "paths": {
    "/": {
      "get": {
        "summary": "Home",
        "operationId": "Home",
        "responses": {
          "200": {
            "description": "Request fulfilled, document follows",
            "headers": {

            },
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Resp"
                }
              }
            }
          }
        },
        "deprecated": false
      }
    }
  },
  "components": {
    "schemas": {
      "Resp": {
        "properties": {
          "foo": {
            "type": "integer"
          }
        },
        "type": "object",
        "required": [
          "foo"
        ],
        "title": "Resp",
        "description": "A response object."
      }
    }
  }
}

It only works if you specify float instead of int.

URL to code causing the issue

No response

MCVE

# Your MCVE code here

Steps to reproduce

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Screenshots

"![SCREENSHOT_DESCRIPTION](SCREENSHOT_LINK.png)"

Logs

Litestar Version

2.13.0 final

Platform

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

[umarbutler]

This persists on 2.14.0.

[umarbutler]

Turns out, this only happens if we're dealing with an int AND the constraint is 0. Super weird.

Temporary solution: gt = 0 -> ge = 1.

But having to do ge = 0 -> gt = -1 for my custom NonNegativeInt type is a bit annoying.

[provinzkraut]

Turns out, this only happens if we're dealing with an int AND the constraint is 0. Super weird.

Mmh. Sounds like the bug could be a not gt check where it should be a gt is not None somewhere.

[umarbutler]

Yes there is a check like that but changing that code didn't fix it either. I suspect there's two layers of checks like that which are making it even trickier.

[umarbutler]

@provinzkraut it also looks like even if I get ge=1 in Meta but I don't also duplicate that in Body() then it won't show up in the spec... for only certain structs?? and for some structs it will show up. Again, only for ints.

Workaround: make sure you define your constraints twice in Meta and Body(). And never let a constraint be 0 if its an int.