Remove boxing from StreamBody (#241)

I just had a thought: Why should `response::Headers` be generic, but
`body::StreamBody` should not? `StreamBody` previously boxed the stream
to erase the generics. So we had `response::Headers<T>` but
`body::StreamBody`, without generics.

After thinking about it I think it actually makes sense for responses to
remain generic because you're able to use `impl IntoResponse` so you
don't have to name the generics.

Whereas in the case of `BodyStream` (an extractor) you cannot use `impl Trait`
so it makes sense to box the inner body to make the type easier to name. Besides,
`BodyStream` is mostly useful when the request body isn't `hyper::Body`, as
that already implements `Stream`.

CHANGELOG.md

@@ -32,6 +32,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - **added:** Add `OriginalUri` for extracting original request URI in nested services ([#197](https://github.com/tokio-rs/axum/pull/197))
   - **added:** Implement `FromRequest` for `http::Extensions` ([#169](https://github.com/tokio-rs/axum/pull/169))
   - **added:** Make `RequestParts::{new, try_into_request}` public so extractors can be used outside axum ([#194](https://github.com/tokio-rs/axum/pull/194))
+  - **added:** Implement `FromRequest` for `axum::body::Body` ([#241](https://github.com/tokio-rs/axum/pull/241))
   - **changed:** Removed `extract::UrlParams` and `extract::UrlParamsMap`. Use `extract::Path` instead ([#154](https://github.com/tokio-rs/axum/pull/154))
   - **changed:** `extractor_middleware` now requires `RequestBody: Default` ([#167](https://github.com/tokio-rs/axum/pull/167))
   - **changed:** Convert `RequestAlreadyExtracted` to an enum with each possible error variant ([#167](https://github.com/tokio-rs/axum/pull/167))

src/body/stream_body.rs

@@ -1,9 +1,12 @@
-use crate::{BoxError, Error};
+use crate::{response::IntoResponse, BoxError, Error};
 use bytes::Bytes;
-use futures_util::stream::{self, Stream, TryStreamExt};
-use http::HeaderMap;
+use futures_util::{
+    ready,
+    stream::{self, TryStream},
+};
+use http::{HeaderMap, Response};
 use http_body::Body;
-use std::convert::Infallible;
+use pin_project_lite::pin_project;
 use std::{
     fmt,
     pin::Pin,
@@ -11,80 +14,108 @@ use std::{
 };
 use sync_wrapper::SyncWrapper;
 
-/// An [`http_body::Body`] created from a [`Stream`].
-///
-/// # Example
-///
-/// ```
-/// use axum::{
-///     Router,
-///     handler::get,
-///     body::StreamBody,
-/// };
-/// use futures::stream;
-///
-/// async fn handler() -> StreamBody {
-///     let chunks: Vec<Result<_, std::io::Error>> = vec![
-///         Ok("Hello,"),
-///         Ok(" "),
-///         Ok("world!"),
-///     ];
-///     let stream = stream::iter(chunks);
-///     StreamBody::new(stream)
-/// }
-///
-/// let app = Router::new().route("/", get(handler));
-/// # async {
-/// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
-/// # };
-/// ```
-///
-/// [`Stream`]: futures_util::stream::Stream
-// this should probably be extracted to `http_body`, eventually...
-pub struct StreamBody {
-    stream: SyncWrapper<Pin<Box<dyn Stream<Item = Result<Bytes, Error>> + Send>>>,
+pin_project! {
+    /// An [`http_body::Body`] created from a [`Stream`].
+    ///
+    /// If purpose of this type is to be used in responses. If you want to
+    /// extract the request body as a stream consider using
+    /// [`extract::BodyStream`].
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use axum::{
+    ///     Router,
+    ///     handler::get,
+    ///     body::StreamBody,
+    ///     response::IntoResponse,
+    /// };
+    /// use futures::stream;
+    ///
+    /// async fn handler() -> impl IntoResponse {
+    ///     let chunks: Vec<Result<_, std::io::Error>> = vec![
+    ///         Ok("Hello,"),
+    ///         Ok(" "),
+    ///         Ok("world!"),
+    ///     ];
+    ///     let stream = stream::iter(chunks);
+    ///     StreamBody::new(stream)
+    /// }
+    ///
+    /// let app = Router::new().route("/", get(handler));
+    /// # async {
+    /// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
+    /// # };
+    /// ```
+    ///
+    /// [`Stream`]: futures_util::stream::Stream
+    pub struct StreamBody<S> {
+        #[pin]
+        stream: SyncWrapper<S>,
+    }
 }
 
-impl StreamBody {
+impl<S> StreamBody<S> {
     /// Create a new `StreamBody` from a [`Stream`].
     ///
     /// [`Stream`]: futures_util::stream::Stream
-    pub fn new<S, T, E>(stream: S) -> Self
+    pub fn new(stream: S) -> Self
     where
-        S: Stream<Item = Result<T, E>> + Send + 'static,
-        T: Into<Bytes> + 'static,
-        E: Into<BoxError> + 'static,
+        S: TryStream + Send + 'static,
+        S::Ok: Into<Bytes>,
+        S::Error: Into<BoxError>,
     {
-        let stream = stream
-            .map_ok(Into::into)
-            .map_err(|err| Error::new(err.into()));
         Self {
-            stream: SyncWrapper::new(Box::pin(stream)),
+            stream: SyncWrapper::new(stream),
         }
     }
 }
 
-impl Default for StreamBody {
-    fn default() -> Self {
-        Self::new(stream::empty::<Result<Bytes, Infallible>>())
+impl<S> IntoResponse for StreamBody<S>
+where
+    S: TryStream + Send + 'static,
+    S::Ok: Into<Bytes>,
+    S::Error: Into<BoxError>,
+{
+    type Body = Self;
+    type BodyError = Error;
+
+    fn into_response(self) -> Response<Self> {
+        Response::new(self)
     }
 }
 
-impl fmt::Debug for StreamBody {
+impl Default for StreamBody<futures_util::stream::Empty<Result<Bytes, Error>>> {
+    fn default() -> Self {
+        Self::new(stream::empty())
+    }
+}
+
+impl<S> fmt::Debug for StreamBody<S> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_tuple("StreamBody").finish()
     }
 }
 
-impl Body for StreamBody {
+impl<S> Body for StreamBody<S>
+where
+    S: TryStream,
+    S::Ok: Into<Bytes>,
+    S::Error: Into<BoxError>,
+{
     type Data = Bytes;
     type Error = Error;
 
     fn poll_data(
-        mut self: Pin<&mut Self>,
+        self: Pin<&mut Self>,
         cx: &mut Context<'_>,
     ) -> Poll<Option<Result<Self::Data, Self::Error>>> {
-        Pin::new(self.stream.get_mut()).poll_next(cx)
+        let stream = self.project().stream.get_pin_mut();
+        match ready!(stream.try_poll_next(cx)) {
+            Some(Ok(chunk)) => Poll::Ready(Some(Ok(chunk.into()))),
+            Some(Err(err)) => Poll::Ready(Some(Err(Error::new(err)))),
+            None => Poll::Ready(None),
+        }
     }
 
     fn poll_trailers(
@@ -97,7 +128,11 @@ impl Body for StreamBody {
 
 #[test]
 fn stream_body_traits() {
-    crate::tests::assert_send::<StreamBody>();
-    crate::tests::assert_sync::<StreamBody>();
-    crate::tests::assert_unpin::<StreamBody>();
+    use futures_util::stream::Empty;
+
+    type EmptyStream = StreamBody<Empty<Result<Bytes, BoxError>>>;
+
+    crate::tests::assert_send::<EmptyStream>();
+    crate::tests::assert_sync::<EmptyStream>();
+    crate::tests::assert_unpin::<EmptyStream>();
 }

src/extract/request_parts.rs

@@ -1,5 +1,5 @@
 use super::{rejection::*, take_body, Extension, FromRequest, RequestParts};
-use crate::{BoxError, Error};
+use crate::{body::Body, BoxError, Error};
 use async_trait::async_trait;
 use bytes::Bytes;
 use futures_util::stream::Stream;
@@ -171,6 +171,11 @@ where
 
 /// Extractor that extracts the request body as a [`Stream`].
 ///
+/// Note if your request body is [`body::Body`] you can extract that directly
+/// and since it already implements [`Stream`] you don't need this type. The
+/// purpose of this type is to extract other types of request bodies as a
+/// [`Stream`].
+///
 /// # Example
 ///
 /// ```rust,no_run
@@ -194,6 +199,7 @@ where
 /// ```
 ///
 /// [`Stream`]: https://docs.rs/futures/latest/futures/stream/trait.Stream.html
+/// [`body::Body`]: crate::body::Body
 pub struct BodyStream(
     SyncWrapper<Pin<Box<dyn http_body::Body<Data = Bytes, Error = Error> + Send + 'static>>>,
 );
@@ -238,6 +244,9 @@ fn body_stream_traits() {
 
 /// Extractor that extracts the raw request body.
 ///
+/// Note that [`body::Body`] can be extracted directly. This purpose of this
+/// type is to extract other types of request bodies.
+///
 /// # Example
 ///
 /// ```rust,no_run
@@ -257,8 +266,10 @@ fn body_stream_traits() {
 /// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
 /// # };
 /// ```
+///
+/// [`body::Body`]: crate::body::Body
 #[derive(Debug, Default, Clone)]
-pub struct RawBody<B = crate::body::Body>(pub B);
+pub struct RawBody<B = Body>(pub B);
 
 #[async_trait]
 impl<B> FromRequest<B> for Bytes
@@ -280,6 +291,15 @@ where
     }
 }
 
+#[async_trait]
+impl FromRequest<Body> for Body {
+    type Rejection = BodyAlreadyExtracted;
+
+    async fn from_request(req: &mut RequestParts<Body>) -> Result<Self, Self::Rejection> {
+        req.take_body().ok_or(BodyAlreadyExtracted)
+    }
+}
+
 #[async_trait]
 impl<B> FromRequest<B> for String
 where

src/response/mod.rs

@@ -198,7 +198,6 @@ macro_rules! impl_into_response_for_body {
 impl_into_response_for_body!(hyper::Body);
 impl_into_response_for_body!(Full<Bytes>);
 impl_into_response_for_body!(Empty<Bytes>);
-impl_into_response_for_body!(crate::body::StreamBody);
 
 impl<E> IntoResponse for http_body::combinators::BoxBody<Bytes, E>
 where