Can't use Option for Query extractor?

[sidoki]

Summary

I want to make the query params optional, but I have struggle since the route handler thrown trait bound error.

Removing the Option type will resolve the error.

This is the handler code:

pub async fn login_form(
    params: Option<Query<QueryParams>>
) -> impl IntoResponse {
    // display login.html form page
    let error_html = match params {
        Some(query) => {
            format!("<p style=\"color: red;\">{}</p>", html_escape::encode_text(&query.error))
        }
        None => String::new(),
    };

    Response::builder()
        .status(http::StatusCode::OK)
        .header("Content-Type", "text/html; charset=utf-8")
        .body(include_str!("login.html").to_string())
        .expect("Failed to build response")
        
}

Thanks in advance!

axum version

0.8.3

[mladedav]

You can do Query<Option<QueryParams>> (which will accept either no query or well formed query but would reject anything that doesn't deserialize depending on your expected query) or you can do Result<Query<QueryParams>, QueryRejection> which works the same as the old Option, you just need to be more explicit.

[jplatte]

Are you sure about Query<Option<Params>>? I would personally always recommend not using Option there at all, instead only on fields of the params (or using #[serde(default)] on fields).

[sidoki]

Thanks both!

@jplatte In my case, I have multiple query params and all of it either need to be defined or not at all.

Defining Option only on fields will require extra validation whether all the query params is exist or not.

But, thanks for the recommendation.