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//! Set a header on the response.
//!
//! The header value to be set may be provided as a fixed value when the
//! middleware is constructed, or determined dynamically based on the response
//! by a closure. See the [`MakeHeaderValue`] trait for details.
//!
//! # Example
//!
//! Setting a header from a fixed value provided when the middleware is constructed:
//!
//! ```
//! use http::{Request, Response, header::{self, HeaderValue}};
//! use tower::{Service, ServiceExt, ServiceBuilder};
//! use tower_http::set_header::SetResponseHeaderLayer;
//! use hyper::Body;
//!
//! # #[tokio::main]
//! # async fn main() -> Result<(), Box<dyn std::error::Error>> {
//! # let render_html = tower::service_fn(|request: Request<Body>| async move {
//! # Ok::<_, std::convert::Infallible>(Response::new(request.into_body()))
//! # });
//! #
//! let mut svc = ServiceBuilder::new()
//! .layer(
//! // Layer that sets `Content-Type: text/html` on responses.
//! //
//! // `if_not_present` will only insert the header if it does not already
//! // have a value.
//! SetResponseHeaderLayer::if_not_present(
//! header::CONTENT_TYPE,
//! HeaderValue::from_static("text/html"),
//! )
//! )
//! .service(render_html);
//!
//! let request = Request::new(Body::empty());
//!
//! let response = svc.ready().await?.call(request).await?;
//!
//! assert_eq!(response.headers()["content-type"], "text/html");
//! #
//! # Ok(())
//! # }
//! ```
//!
//! Setting a header based on a value determined dynamically from the response:
//!
//! ```
//! use http::{Request, Response, header::{self, HeaderValue}};
//! use tower::{Service, ServiceExt, ServiceBuilder};
//! use tower_http::set_header::SetResponseHeaderLayer;
//! use hyper::Body;
//! use http_body::Body as _; // for `Body::size_hint`
//!
//! # #[tokio::main]
//! # async fn main() -> Result<(), Box<dyn std::error::Error>> {
//! # let render_html = tower::service_fn(|request: Request<Body>| async move {
//! # Ok::<_, std::convert::Infallible>(Response::new(Body::from("1234567890")))
//! # });
//! #
//! let mut svc = ServiceBuilder::new()
//! .layer(
//! // Layer that sets `Content-Length` if the body has a known size.
//! // Bodies with streaming responses wont have a known size.
//! //
//! // `overriding` will insert the header and override any previous values it
//! // may have.
//! SetResponseHeaderLayer::overriding(
//! header::CONTENT_LENGTH,
//! |response: &Response<Body>| {
//! if let Some(size) = response.body().size_hint().exact() {
//! // If the response body has a known size, returning `Some` will
//! // set the `Content-Length` header to that value.
//! Some(HeaderValue::from_str(&size.to_string()).unwrap())
//! } else {
//! // If the response body doesn't have a known size, return `None`
//! // to skip setting the header on this response.
//! None
//! }
//! }
//! )
//! )
//! .service(render_html);
//!
//! let request = Request::new(Body::empty());
//!
//! let response = svc.ready().await?.call(request).await?;
//!
//! assert_eq!(response.headers()["content-length"], "10");
//! #
//! # Ok(())
//! # }
//! ```
use super::{InsertHeaderMode, MakeHeaderValue};
use futures_util::ready;
use http::{header::HeaderName, Request, Response};
use pin_project_lite::pin_project;
use std::{
fmt,
future::Future,
pin::Pin,
task::{Context, Poll},
};
use tower_layer::Layer;
use tower_service::Service;
/// Layer that applies [`SetResponseHeader`] which adds a response header.
///
/// See [`SetResponseHeader`] for more details.
pub struct SetResponseHeaderLayer<M> {
header_name: HeaderName,
make: M,
mode: InsertHeaderMode,
}
impl<M> fmt::Debug for SetResponseHeaderLayer<M> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("SetResponseHeaderLayer")
.field("header_name", &self.header_name)
.field("mode", &self.mode)
.field("make", &std::any::type_name::<M>())
.finish()
}
}
impl<M> SetResponseHeaderLayer<M> {
/// Create a new [`SetResponseHeaderLayer`].
///
/// If a previous value exists for the same header, it is removed and replaced with the new
/// header value.
pub fn overriding(header_name: HeaderName, make: M) -> Self {
Self::new(header_name, make, InsertHeaderMode::Override)
}
/// Create a new [`SetResponseHeaderLayer`].
///
/// The new header is always added, preserving any existing values. If previous values exist,
/// the header will have multiple values.
pub fn appending(header_name: HeaderName, make: M) -> Self {
Self::new(header_name, make, InsertHeaderMode::Append)
}
/// Create a new [`SetResponseHeaderLayer`].
///
/// If a previous value exists for the header, the new value is not inserted.
pub fn if_not_present(header_name: HeaderName, make: M) -> Self {
Self::new(header_name, make, InsertHeaderMode::IfNotPresent)
}
fn new(header_name: HeaderName, make: M, mode: InsertHeaderMode) -> Self {
Self {
make,
header_name,
mode,
}
}
}
impl<S, M> Layer<S> for SetResponseHeaderLayer<M>
where
M: Clone,
{
type Service = SetResponseHeader<S, M>;
fn layer(&self, inner: S) -> Self::Service {
SetResponseHeader {
inner,
header_name: self.header_name.clone(),
make: self.make.clone(),
mode: self.mode,
}
}
}
impl<M> Clone for SetResponseHeaderLayer<M>
where
M: Clone,
{
fn clone(&self) -> Self {
Self {
make: self.make.clone(),
header_name: self.header_name.clone(),
mode: self.mode,
}
}
}
/// Middleware that sets a header on the response.
#[derive(Clone)]
pub struct SetResponseHeader<S, M> {
inner: S,
header_name: HeaderName,
make: M,
mode: InsertHeaderMode,
}
impl<S, M> SetResponseHeader<S, M> {
/// Create a new [`SetResponseHeader`].
///
/// If a previous value exists for the same header, it is removed and replaced with the new
/// header value.
pub fn overriding(inner: S, header_name: HeaderName, make: M) -> Self {
Self::new(inner, header_name, make, InsertHeaderMode::Override)
}
/// Create a new [`SetResponseHeader`].
///
/// The new header is always added, preserving any existing values. If previous values exist,
/// the header will have multiple values.
pub fn appending(inner: S, header_name: HeaderName, make: M) -> Self {
Self::new(inner, header_name, make, InsertHeaderMode::Append)
}
/// Create a new [`SetResponseHeader`].
///
/// If a previous value exists for the header, the new value is not inserted.
pub fn if_not_present(inner: S, header_name: HeaderName, make: M) -> Self {
Self::new(inner, header_name, make, InsertHeaderMode::IfNotPresent)
}
fn new(inner: S, header_name: HeaderName, make: M, mode: InsertHeaderMode) -> Self {
Self {
inner,
header_name,
make,
mode,
}
}
define_inner_service_accessors!();
}
impl<S, M> fmt::Debug for SetResponseHeader<S, M>
where
S: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("SetResponseHeader")
.field("inner", &self.inner)
.field("header_name", &self.header_name)
.field("mode", &self.mode)
.field("make", &std::any::type_name::<M>())
.finish()
}
}
impl<ReqBody, ResBody, S, M> Service<Request<ReqBody>> for SetResponseHeader<S, M>
where
S: Service<Request<ReqBody>, Response = Response<ResBody>>,
M: MakeHeaderValue<Response<ResBody>> + Clone,
{
type Response = S::Response;
type Error = S::Error;
type Future = ResponseFuture<S::Future, M>;
#[inline]
fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
self.inner.poll_ready(cx)
}
fn call(&mut self, req: Request<ReqBody>) -> Self::Future {
ResponseFuture {
future: self.inner.call(req),
header_name: self.header_name.clone(),
make: self.make.clone(),
mode: self.mode,
}
}
}
pin_project! {
/// Response future for [`SetResponseHeader`].
#[derive(Debug)]
pub struct ResponseFuture<F, M> {
#[pin]
future: F,
header_name: HeaderName,
make: M,
mode: InsertHeaderMode,
}
}
impl<F, ResBody, E, M> Future for ResponseFuture<F, M>
where
F: Future<Output = Result<Response<ResBody>, E>>,
M: MakeHeaderValue<Response<ResBody>>,
{
type Output = F::Output;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let this = self.project();
let mut res = ready!(this.future.poll(cx)?);
this.mode.apply(this.header_name, &mut res, &mut *this.make);
Poll::Ready(Ok(res))
}
}
#[cfg(test)]
mod tests {
use super::*;
use http::{header, HeaderValue};
use hyper::Body;
use std::convert::Infallible;
use tower::{service_fn, ServiceExt};
#[tokio::test]
async fn test_override_mode() {
let svc = SetResponseHeader::overriding(
service_fn(|_req: Request<Body>| async {
let res = Response::builder()
.header(header::CONTENT_TYPE, "good-content")
.body(Body::empty())
.unwrap();
Ok::<_, Infallible>(res)
}),
header::CONTENT_TYPE,
HeaderValue::from_static("text/html"),
);
let res = svc.oneshot(Request::new(Body::empty())).await.unwrap();
let mut values = res.headers().get_all(header::CONTENT_TYPE).iter();
assert_eq!(values.next().unwrap(), "text/html");
assert_eq!(values.next(), None);
}
#[tokio::test]
async fn test_append_mode() {
let svc = SetResponseHeader::appending(
service_fn(|_req: Request<Body>| async {
let res = Response::builder()
.header(header::CONTENT_TYPE, "good-content")
.body(Body::empty())
.unwrap();
Ok::<_, Infallible>(res)
}),
header::CONTENT_TYPE,
HeaderValue::from_static("text/html"),
);
let res = svc.oneshot(Request::new(Body::empty())).await.unwrap();
let mut values = res.headers().get_all(header::CONTENT_TYPE).iter();
assert_eq!(values.next().unwrap(), "good-content");
assert_eq!(values.next().unwrap(), "text/html");
assert_eq!(values.next(), None);
}
#[tokio::test]
async fn test_skip_if_present_mode() {
let svc = SetResponseHeader::if_not_present(
service_fn(|_req: Request<Body>| async {
let res = Response::builder()
.header(header::CONTENT_TYPE, "good-content")
.body(Body::empty())
.unwrap();
Ok::<_, Infallible>(res)
}),
header::CONTENT_TYPE,
HeaderValue::from_static("text/html"),
);
let res = svc.oneshot(Request::new(Body::empty())).await.unwrap();
let mut values = res.headers().get_all(header::CONTENT_TYPE).iter();
assert_eq!(values.next().unwrap(), "good-content");
assert_eq!(values.next(), None);
}
#[tokio::test]
async fn test_skip_if_present_mode_when_not_present() {
let svc = SetResponseHeader::if_not_present(
service_fn(|_req: Request<Body>| async {
let res = Response::builder().body(Body::empty()).unwrap();
Ok::<_, Infallible>(res)
}),
header::CONTENT_TYPE,
HeaderValue::from_static("text/html"),
);
let res = svc.oneshot(Request::new(Body::empty())).await.unwrap();
let mut values = res.headers().get_all(header::CONTENT_TYPE).iter();
assert_eq!(values.next().unwrap(), "text/html");
assert_eq!(values.next(), None);
}
}