Enhancement: Support OpenAPI examples defined in Structs, Pydantic models and dataclasses

[bogdanteleaga]

Description

Examples provided on json parameter fields do not get rendered in the Swagger UI.

The /schema/openapi.json does get generated similarly to https://github.com/litestar-org/litestar/pull/2660, but it seems this does not result in the examples being actually rendered in the Swagger UI.

I included examples for defining the classes with any of pydantic, msgspec and dataclass.

URL to code causing the issue

No response

MCVE

from litestar import post, Litestar
from typing import Annotated
from msgspec import Struct, Meta


class Lookup(Struct):
    id: Annotated[str, Meta(examples=["example-1", "example-2"])]

#class Lookup(BaseModel):
#    id: Annotated[str, Field(json_schema_extra={"example": "example-1"})

#@dataclass
#class Lookup:
#    id: Annotated[str, Parameter(examples=[Example(value="example-1"), Example(value="example-2")])


@post(path="/lookup")
async def lookup(lookup: Lookup) -> Lookup:
    return Lookup(id=lookup.id)


app = Litestar(route_handlers=[lookup])

Steps to reproduce

1. Go to `http://127.0.0.1:8000/schema/swagger`
2. Click on `/lookup`
3. Scroll down to examples
4. They are missing

Screenshots

"![SCREENSHOT_DESCRIPTION](SCREENSHOT_LINK.png)"

Logs

No response

Litestar Version

2.4.2

Platform

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

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[provinzkraut]

Hey @bogdanteleaga, I've re-labelled this as an enhancement, since it's not really a bug; Declaring examples this way is simply not supported at the moment, but it's a reasonable feature to add.

[bogdanteleaga]

If I remember correctly this used to work before the rename. Maybe that came with a bigger change than expected, but that's the main reason I considered it to be a bug.

Looking at the other issue I still don't see an answer to the initial question: there is no way currently to set examples for the request body?

[provinzkraut]

If I remember correctly this used to work before the rename. Maybe that came with a bigger change than expected, but that's the main reason I considered it to be a bug.

That was in version 1.x, so it's considered a breaking change. The reason it used to work is that back then, the schema generation was done by Pydantic, which was good for Pydantic models, but tricky when you wanted to use other libraries such as msgspec or attrs. Now we're doing the schema generation ourselves, which has enabled a lot more features, but there's of course also some drawbacks and room for improvement, which this would fall under.

Looking at the other issue I still don't see an answer to the initial question: there is no way currently to set examples for the request body?

Sure, you can. You'll simply have to write it out explicitly:

from litestar import post, Litestar
from typing import Annotated

from litestar.openapi.spec import Example
from litestar.params import BodyKwarg
from dataclasses import dataclass


@dataclass
class Foo:
    bar: str


@post("/")
async def handler(
    data: Annotated[
        Foo,
        BodyKwarg(
            examples=[
                Example(summary="This is how to use the body", value="some string")
            ]
        ),
    ]
) -> None:
    pass

[bogdanteleaga]

Thank you for this example, but if Foo has several different attributes is it possible to set examples for each of them?

[tuukkamustonen]

@bogdanteleaga You can set e.g. value={"attr": 1, "another": 2}, and you can give a list of examples for the different variations.

[bogdanteleaga]

So the example above rewritten like this

@dataclass
class Foo:
    foo: str
    bar: str


@post("/")
async def handler(
    data: Annotated[
        Foo,
        BodyKwarg(
            examples=[
                Example(
                    summary="This is how to use the body",
                    value={"foo": "a", "bar": "b"},
                )
            ]
        ),
    ]
) -> None:
    pass

Results in this within the swagger UI

{
  "foo": "string",
  "bar": "string"
}

[github-actions[bot]]

A fix for this issue has been released in v2.7.1