actix-web/src/middleware/default_headers.rs

//! For middleware documentation, see [`DefaultHeaders`].

use std::{
    convert::TryFrom,
    future::Future,
    marker::PhantomData,
    pin::Pin,
    rc::Rc,
    task::{Context, Poll},
};

use actix_utils::future::{ready, Ready};
use futures_core::ready;

use crate::{
    dev::{Service, Transform},
    http::{
        header::{HeaderName, HeaderValue, CONTENT_TYPE},
        Error as HttpError, HeaderMap,
    },
    service::{ServiceRequest, ServiceResponse},
    Error,
};

/// Middleware for setting default response headers.
///
/// Headers with the same key that are already set in a response will *not* be overwritten.
///
/// # Examples
/// ```
/// use actix_web::{web, http, middleware, App, HttpResponse};
///
/// fn main() {
///     let app = App::new()
///         .wrap(middleware::DefaultHeaders::new().header("X-Version", "0.2"))
///         .service(
///             web::resource("/test")
///                 .route(web::get().to(|| HttpResponse::Ok()))
///                 .route(web::method(http::Method::HEAD).to(|| HttpResponse::MethodNotAllowed()))
///         );
/// }
/// ```
#[derive(Clone)]
pub struct DefaultHeaders {
    inner: Rc<Inner>,
}

struct Inner {
    headers: HeaderMap,
}

impl Default for DefaultHeaders {
    fn default() -> Self {
        DefaultHeaders {
            inner: Rc::new(Inner {
                headers: HeaderMap::new(),
            }),
        }
    }
}

impl DefaultHeaders {
    /// Constructs an empty `DefaultHeaders` middleware.
    pub fn new() -> DefaultHeaders {
        DefaultHeaders::default()
    }

    /// Adds a header to the default set.
    #[inline]
    pub fn header<K, V>(mut self, key: K, value: V) -> Self
    where
        HeaderName: TryFrom<K>,
        <HeaderName as TryFrom<K>>::Error: Into<HttpError>,
        HeaderValue: TryFrom<V>,
        <HeaderValue as TryFrom<V>>::Error: Into<HttpError>,
    {
        #[allow(clippy::match_wild_err_arm)]
        match HeaderName::try_from(key) {
            Ok(key) => match HeaderValue::try_from(value) {
                Ok(value) => {
                    Rc::get_mut(&mut self.inner)
                        .expect("Multiple copies exist")
                        .headers
                        .append(key, value);
                }
                Err(_) => panic!("Can not create header value"),
            },
            Err(_) => panic!("Can not create header name"),
        }
        self
    }

    /// Adds a default *Content-Type* header if response does not contain one.
    ///
    /// Default is `application/octet-stream`.
    pub fn add_content_type(mut self) -> Self {
        Rc::get_mut(&mut self.inner)
            .expect("Multiple `Inner` copies exist.")
            .headers
            .insert(
                CONTENT_TYPE,
                HeaderValue::from_static("application/octet-stream"),
            );

        self
    }
}

impl<S, B> Transform<S, ServiceRequest> for DefaultHeaders
where
    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
    S::Future: 'static,
{
    type Response = ServiceResponse<B>;
    type Error = Error;
    type Transform = DefaultHeadersMiddleware<S>;
    type InitError = ();
    type Future = Ready<Result<Self::Transform, Self::InitError>>;

    fn new_transform(&self, service: S) -> Self::Future {
        ready(Ok(DefaultHeadersMiddleware {
            service,
            inner: self.inner.clone(),
        }))
    }
}

pub struct DefaultHeadersMiddleware<S> {
    service: S,
    inner: Rc<Inner>,
}

impl<S, B> Service<ServiceRequest> for DefaultHeadersMiddleware<S>
where
    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
    S::Future: 'static,
{
    type Response = ServiceResponse<B>;
    type Error = Error;
    type Future = DefaultHeaderFuture<S, B>;

    actix_service::forward_ready!(service);

    fn call(&self, req: ServiceRequest) -> Self::Future {
        let inner = self.inner.clone();
        let fut = self.service.call(req);

        DefaultHeaderFuture {
            fut,
            inner,
            _body: PhantomData,
        }
    }
}

#[pin_project::pin_project]
pub struct DefaultHeaderFuture<S: Service<ServiceRequest>, B> {
    #[pin]
    fut: S::Future,
    inner: Rc<Inner>,
    _body: PhantomData<B>,
}

impl<S, B> Future for DefaultHeaderFuture<S, B>
where
    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
{
    type Output = <S::Future as Future>::Output;

    #[allow(clippy::borrow_interior_mutable_const)]
    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let this = self.project();
        let mut res = ready!(this.fut.poll(cx))?;

        // set response headers
        for (key, value) in this.inner.headers.iter() {
            if !res.headers().contains_key(key) {
                res.headers_mut().insert(key.clone(), value.clone());
            }
        }

        Poll::Ready(Ok(res))
    }
}

#[cfg(test)]
mod tests {
    use actix_service::IntoService;
    use actix_utils::future::ok;

    use super::*;
    use crate::{
        dev::ServiceRequest,
        http::header::CONTENT_TYPE,
        test::{ok_service, TestRequest},
        HttpResponse,
    };

    #[actix_rt::test]
    async fn test_default_headers() {
        let mw = DefaultHeaders::new()
            .header(CONTENT_TYPE, "0001")
            .new_transform(ok_service())
            .await
            .unwrap();

        let req = TestRequest::default().to_srv_request();
        let resp = mw.call(req).await.unwrap();
        assert_eq!(resp.headers().get(CONTENT_TYPE).unwrap(), "0001");

        let req = TestRequest::default().to_srv_request();
        let srv = |req: ServiceRequest| {
            ok(req.into_response(
                HttpResponse::Ok()
                    .insert_header((CONTENT_TYPE, "0002"))
                    .finish(),
            ))
        };
        let mw = DefaultHeaders::new()
            .header(CONTENT_TYPE, "0001")
            .new_transform(srv.into_service())
            .await
            .unwrap();
        let resp = mw.call(req).await.unwrap();
        assert_eq!(resp.headers().get(CONTENT_TYPE).unwrap(), "0002");
    }

    #[actix_rt::test]
    async fn test_content_type() {
        let srv = |req: ServiceRequest| ok(req.into_response(HttpResponse::Ok().finish()));
        let mw = DefaultHeaders::new()
            .add_content_type()
            .new_transform(srv.into_service())
            .await
            .unwrap();

        let req = TestRequest::default().to_srv_request();
        let resp = mw.call(req).await.unwrap();
        assert_eq!(
            resp.headers().get(CONTENT_TYPE).unwrap(),
            "application/octet-stream"
        );
    }
}