Using local_cache to forward a Guard's error to a catcher

[AaronCarton]

I currently have an Auth guard that checkes whether a valid bearer token is included

#[rocket::async_trait]
impl<'r> FromRequest<'r> for AuthGuard {
    type Error = Json<&'static str>;

    async fn from_request(req: &'r Request<'_>) -> request::Outcome<Self, Self::Error> {
        // get the server state
        let state = req.guard::<&State<ServerState>>().await.unwrap();

        // get the bearer token from the request
        let token = req.guard::<BearerToken>().await;

        // check if token is missing
        if token.is_failure() {
            println!("Authentication failed. Missing token.");
            return Outcome::Failure((
                Status::Forbidden,
                Json("Authentication failed. Missing token."),
            ));
        }

        // verify the token
        match state.auth.verify(&token.unwrap()).await {
            Ok(token) => {
                let uid = &token.uid;
                println!("Authentication succeeded with uid={}", uid);
                Outcome::Success(AuthGuard { uid: uid.clone() })
            }
            Err(_) => {
                println!("Authentication failed.");
                Outcome::Failure((
                    Status::Forbidden,
                    Json("Authentication failed. Invalid token."),
                ))
            }
        }
    }
}

Upon failure it'll return 403 forbidden, along with some JSON explaining what went wrong.

Now while the console displays this error

But the response still gives the default 403 error

{
    "error": {
        "code": 403,
        "reason": "Forbidden",
        "description": "The server refused to authorize the request."
    }
}

I'm not sure how to make the response reflect the AuthGuard's error description. I know that there's error catchers but those seem too general for my case since they seemingly can't access the AuthGuard's result either?

[AaronCarton]

I discovered that some people use local_cache to store their custom error message, to then retrieve it in the catcher fn.
Although I'm having trouble figuring out how to properly store something in local_cache, and more importantly get it back out out the cache?