How to print all request headers?

[elliotwaite]

When I run this app to try to print all the request headers:

from litestar import Litestar, get
from litestar.datastructures import Headers


@get("/", sync_to_thread=False)
def index(headers: Headers) -> str:
    print("headers:", headers.to_header_list())
    return "Hello, world!"


app = Litestar([index])

... I get the following error:

{"status_code":400,"detail":"Validation failed for GET http://127.0.0.1:8000/","extra":[{"message":"Unsupported type: <class 'dict'>","key":"headers"}]}

I feel like I'm misunderstanding something. Can anyone point out what I'm doing wrong?

Also, the Default signature namespace section of the docs mentions that I can place the Headers import inside an if TYPE_CHECKING: block. But when I do this:

from typing import TYPE_CHECKING

from litestar import Litestar, get

if TYPE_CHECKING:
    from litestar.datastructures import Headers


@get("/", sync_to_thread=False)
def index(headers: Headers) -> str:
    print("headers:", headers.to_header_list())
    return "Hello, world!"


app = Litestar([index])

... I get the following error when I try to run the app:

  ...
  File "/.../app.py", line 10, in <module>
    def index(headers: Headers) -> str:
                       ^^^^^^^
NameError: name 'Headers' is not defined

Am I doing something wrong here as well?

I'm using Litestar version 2.4.3.

[FHU-yezi]

Try wrapping Headers with quotes?

[elliotwaite]

Thanks. Changing header: Headers to header: "Headers" fixed the second issue related to using the if TYPE_CHECKING: block.

However, I am still running into the first issue, related to the Validation failed ... error.

[Alc-Alc]

Does this do it for you?

from litestar import Litestar, get, Request

@get("/", sync_to_thread=False)
def index(request: Request) -> str:
    print("headers:", request.headers.to_header_list())
    return "Hello, world!"

app = Litestar([index])

[provinzkraut]

Hi @elliotwaite, unfortunately, you've come across a bug that can't be fixed until version 3 because it would constitute a breaking change; The headers injected into the route handler via the headers parameter isn't actually a Headers instance but a dict. For now, if you need access to a Headers instance, you'll have to use the method @Alc-Alc provided. If you're fine with a dict, you can just type headers as a dict.

[elliotwaite]

Okay, got it. Thanks!

Both options worked for me:

• Using request: Request and print("headers:", request.headers.to_header_list())
• Or using headers: dict and print("headers:", headers)

I created a PR here to update the docs to mention that the type of headers is a dict instead of an instance of Headers.