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use super::{IntoResponse, Response};
use http::{
header::{HeaderMap, HeaderName, HeaderValue},
Extensions, StatusCode,
};
use std::{convert::Infallible, fmt};
/// Trait for adding headers and extensions to a response.
///
/// # Example
///
/// ```rust
/// use axum::{
/// response::{ResponseParts, IntoResponse, IntoResponseParts, Response},
/// http::{StatusCode, header::{HeaderName, HeaderValue}},
/// };
///
/// // Hypothetical helper type for setting a single header
/// struct SetHeader<'a>(&'a str, &'a str);
///
/// impl<'a> IntoResponseParts for SetHeader<'a> {
/// type Error = (StatusCode, String);
///
/// fn into_response_parts(self, mut res: ResponseParts) -> Result<ResponseParts, Self::Error> {
/// match (self.0.parse::<HeaderName>(), self.1.parse::<HeaderValue>()) {
/// (Ok(name), Ok(value)) => {
/// res.headers_mut().insert(name, value);
/// },
/// (Err(_), _) => {
/// return Err((
/// StatusCode::INTERNAL_SERVER_ERROR,
/// format!("Invalid header name {}", self.0),
/// ));
/// },
/// (_, Err(_)) => {
/// return Err((
/// StatusCode::INTERNAL_SERVER_ERROR,
/// format!("Invalid header value {}", self.1),
/// ));
/// },
/// }
///
/// Ok(res)
/// }
/// }
///
/// // It's also recommended to implement `IntoResponse` so `SetHeader` can be used on its own as
/// // the response
/// impl<'a> IntoResponse for SetHeader<'a> {
/// fn into_response(self) -> Response {
/// // This gives an empty response with the header
/// (self, ()).into_response()
/// }
/// }
///
/// // We can now return `SetHeader` in responses
/// //
/// // Note that returning `impl IntoResponse` might be easier if the response has many parts to
/// // it. The return type is written out here for clarity.
/// async fn handler() -> (SetHeader<'static>, SetHeader<'static>, &'static str) {
/// (
/// SetHeader("server", "axum"),
/// SetHeader("x-foo", "custom"),
/// "body",
/// )
/// }
///
/// // Or on its own as the whole response
/// async fn other_handler() -> SetHeader<'static> {
/// SetHeader("x-foo", "custom")
/// }
/// ```
pub trait IntoResponseParts {
/// The type returned in the event of an error.
///
/// This can be used to fallibly convert types into headers or extensions.
type Error: IntoResponse;
/// Set parts of the response
fn into_response_parts(self, res: ResponseParts) -> Result<ResponseParts, Self::Error>;
}
impl<T> IntoResponseParts for Option<T>
where
T: IntoResponseParts,
{
type Error = T::Error;
fn into_response_parts(self, res: ResponseParts) -> Result<ResponseParts, Self::Error> {
if let Some(inner) = self {
inner.into_response_parts(res)
} else {
Ok(res)
}
}
}
/// Parts of a response.
///
/// Used with [`IntoResponseParts`].
#[derive(Debug)]
pub struct ResponseParts {
pub(crate) res: Response,
}
impl ResponseParts {
/// Gets a reference to the response headers.
#[must_use]
pub fn headers(&self) -> &HeaderMap {
self.res.headers()
}
/// Gets a mutable reference to the response headers.
#[must_use]
pub fn headers_mut(&mut self) -> &mut HeaderMap {
self.res.headers_mut()
}
/// Gets a reference to the response extensions.
#[must_use]
pub fn extensions(&self) -> &Extensions {
self.res.extensions()
}
/// Gets a mutable reference to the response extensions.
#[must_use]
pub fn extensions_mut(&mut self) -> &mut Extensions {
self.res.extensions_mut()
}
}
impl IntoResponseParts for HeaderMap {
type Error = Infallible;
fn into_response_parts(self, mut res: ResponseParts) -> Result<ResponseParts, Self::Error> {
res.headers_mut().extend(self);
Ok(res)
}
}
impl<K, V, const N: usize> IntoResponseParts for [(K, V); N]
where
K: TryInto<HeaderName>,
K::Error: fmt::Display,
V: TryInto<HeaderValue>,
V::Error: fmt::Display,
{
type Error = TryIntoHeaderError<K::Error, V::Error>;
fn into_response_parts(self, mut res: ResponseParts) -> Result<ResponseParts, Self::Error> {
for (key, value) in self {
let key = key.try_into().map_err(TryIntoHeaderError::key)?;
let value = value.try_into().map_err(TryIntoHeaderError::value)?;
res.headers_mut().insert(key, value);
}
Ok(res)
}
}
/// Error returned if converting a value to a header fails.
#[derive(Debug)]
pub struct TryIntoHeaderError<K, V> {
kind: TryIntoHeaderErrorKind<K, V>,
}
impl<K, V> TryIntoHeaderError<K, V> {
pub(super) fn key(err: K) -> Self {
Self {
kind: TryIntoHeaderErrorKind::Key(err),
}
}
pub(super) fn value(err: V) -> Self {
Self {
kind: TryIntoHeaderErrorKind::Value(err),
}
}
}
#[derive(Debug)]
enum TryIntoHeaderErrorKind<K, V> {
Key(K),
Value(V),
}
impl<K, V> IntoResponse for TryIntoHeaderError<K, V>
where
K: fmt::Display,
V: fmt::Display,
{
fn into_response(self) -> Response {
match self.kind {
TryIntoHeaderErrorKind::Key(inner) => {
(StatusCode::INTERNAL_SERVER_ERROR, inner.to_string()).into_response()
}
TryIntoHeaderErrorKind::Value(inner) => {
(StatusCode::INTERNAL_SERVER_ERROR, inner.to_string()).into_response()
}
}
}
}
impl<K, V> fmt::Display for TryIntoHeaderError<K, V> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self.kind {
TryIntoHeaderErrorKind::Key(_) => write!(f, "failed to convert key to a header name"),
TryIntoHeaderErrorKind::Value(_) => {
write!(f, "failed to convert value to a header value")
}
}
}
}
impl<K, V> std::error::Error for TryIntoHeaderError<K, V>
where
K: std::error::Error + 'static,
V: std::error::Error + 'static,
{
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
match &self.kind {
TryIntoHeaderErrorKind::Key(inner) => Some(inner),
TryIntoHeaderErrorKind::Value(inner) => Some(inner),
}
}
}
macro_rules! impl_into_response_parts {
( $($ty:ident),* $(,)? ) => {
#[allow(non_snake_case)]
impl<$($ty,)*> IntoResponseParts for ($($ty,)*)
where
$( $ty: IntoResponseParts, )*
{
type Error = Response;
fn into_response_parts(self, res: ResponseParts) -> Result<ResponseParts, Self::Error> {
let ($($ty,)*) = self;
$(
let res = match $ty.into_response_parts(res) {
Ok(res) => res,
Err(err) => {
return Err(err.into_response());
}
};
)*
Ok(res)
}
}
}
}
all_the_tuples_no_last_special_case!(impl_into_response_parts);
impl IntoResponseParts for Extensions {
type Error = Infallible;
fn into_response_parts(self, mut res: ResponseParts) -> Result<ResponseParts, Self::Error> {
res.extensions_mut().extend(self);
Ok(res)
}
}
impl IntoResponseParts for () {
type Error = Infallible;
fn into_response_parts(self, res: ResponseParts) -> Result<ResponseParts, Self::Error> {
Ok(res)
}
}