Modifying HTTP Headers

Most of the time, you shouldn't need to touch the HTTP headers of your Perseus templates, but sometimes you will need to. A particular example of this is if you want your users' browsers to only cache a page for a certain amount of time (the default for Perseus if five minutes), then you'd need to set the Cache-Control header.

Perseus supports inserting arbitrary HTTP headers for any response from the server that successfully returns a page generated from the template those headers are defined for. You can do this like so (taken from here):

use perseus::{
    http::header::{HeaderMap, HeaderName},
    Html, RenderFnResultWithCause, Template,
};
use sycamore::prelude::{view, SsrNode, View};

#[perseus::make_rx(PageStateRx)]
struct PageState {
    greeting: String,
}

#[perseus::template_rx]
pub fn index_page(state: PageStateRx) -> View<G> {
    view! {
        p { (state.greeting.get()) }
    }
}

#[perseus::head]
pub fn head() -> View<SsrNode> {
    view! {
        title { "Index Page" }
    }
}

pub fn get_template<G: Html>() -> Template<G> {
    Template::new("index")
        .template(index_page)
        .head(head)
        .build_state_fn(get_build_state)
        .set_headers_fn(set_headers)
}

#[perseus::autoserde(build_state)]
pub async fn get_build_state(_path: String, _locale: String) -> RenderFnResultWithCause<PageState> {
    Ok(PageState {
        greeting: "Hello World!".to_string(),
    })
}

// For legacy reasons, this takes an `Option<T>`, but, if you're generating state, it will always be here
// In v0.4.0, this will be updated to take just your page's state (if it has any)
#[perseus::autoserde(set_headers)]
pub fn set_headers(state: Option<PageState>) -> HeaderMap {
    let mut map = HeaderMap::new();
    map.insert(
        HeaderName::from_lowercase(b"x-greeting").unwrap(),
        state.unwrap().greeting.parse().unwrap(),
    );
    map
}

Of note here is the set_headers_fn function, which returns a HeaderMap. This is then used on the template with .set_headers_fn(). Note that the function you provide will be given the state as an argument (ignored here, but it will be deserialized for you with #[perseus::autoserde(set_headers)]), and you must return some headers (you can't return an error).