Summary

https://docs.litestar.dev/2/usage/requests.html#request-body states that:

The type of data an be any supported type, including

• dataclasses
• TypedDicts
• Pydantic models
• Arbitrary stdlib types
• Typed supported via plugins

1. It's not obvious how dataclasses (and TypedDicts and Pydantic models) are supported
2. Link to plugins leads to the page that explain the plugin architecture - where is the list for seeing which plugins exist / are enabled?
3. Pydantic support is actually implemented as a plugin, but it's in the "standard list" above

More on 1:

By "support for dataclasses/TypedDicts" you'd expect to be able to declare OpenAPI constraints and extra validations somehow, e.g.:

import json
from dataclasses import dataclass, field
from typing import Annotated

from litestar import post
from litestar.app import Litestar
from litestar.params import Parameter, KwargDefinition


@dataclass
class DataBody:
    foo1: Annotated[str, Parameter(description="ipsum", gt=1)] = "dummy"
    foo2: Annotated[str, Parameter(description="ipsum", gt=1)] = field(default="dummy")


@dataclass
class DictBody:
    foo1: Annotated[str, KwargDefinition(description="ipsum", gt=1)]
    foo2: Annotated[str, KwargDefinition(default="hello")]  # marked as required


@post("/1")
async def handler1(data: DataBody) -> None: ...


@post("/2")
async def handler2(data: DictBody) -> None: ...


app = Litestar([handler1, handler2])

print(json.dumps(app.openapi_schema.to_schema(), indent=4))

The generated OpenAPI schema output is missing default in many cases (but that's a separate issue, see #3201).

The thing is, how can you:

• Define the OpenAPI constraints for TypedDicts and dataclasses?
• Define custom validations for them?

Pydantic models have Field, Msgspec has Meta. Dataclasses have dataclass.field but you cannot specify OpenAPI constraints through that. TypedDicts don't have that, and cannot even have default values.

It would appear that you can just use Parameter or KwargDefinition in TypedDicts and dataclasses as shown in the above snippet, and maybe it (mostly) works? But this should be instructed in the docs (and decision made if that is intended as supported or not). Also, that would allow to define a default also for TypedDict (via KwargDefinition(default=...) but then that actually doesn't work. Misleading APIs like that should be blocked (although maybe that's a quite special case).