Add tokio feature & make tokio optional for WASM support (#1382)

* add server feature and make tokio and hyper/server and tcp optional

* address review comments

* don't mention any specific runtimes in the example

* sort deps

* add `tokio` feature when adding `ws`

* don't always pull in tower feature that pulls in tokio io stuff

* remove usage of `tokio_cr`

* changelog

* depend on tokio version that supports wasm

* don't make it sound like tokio doesn't support wasm

* call out new default feature

Co-authored-by: Fisher Darling <fdarlingco@gmail.com>
Co-authored-by: David Pedersen <david.pdrsn@gmail.com>

.github/workflows/CI.yml

@@ -209,6 +209,26 @@ jobs:
           -p axum-macros
           --target armv5te-unknown-linux-musleabi
 
+  wasm32-unknown-unknown:
+    needs: check
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        target: wasm32-unknown-unknown
+        override: true
+        profile: minimal
+    - uses: Swatinem/rust-cache@v1
+    - name: Check
+      uses: actions-rs/cargo@v1
+      with:
+        command: check
+        args: >
+          --manifest-path ./examples/simple-router-wasm/Cargo.toml
+          --target wasm32-unknown-unknown
+
   dependencies-are-sorted:
     runs-on: ubuntu-latest
     strategy:

axum/CHANGELOG.md

@@ -33,9 +33,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   can be nested or merged into a `Router` with the same state type ([#1368])
 - **changed:** `Router::nest` now only accepts `Router`s, the general-purpose
   `Service` nesting method has been renamed to `nest_service` ([#1368])
+- **added:** Support compiling to WASM. See the `simple-router-wasm` example
+  for more details ([#1382])
+- **breaking:** New `tokio` default feature needed for WASM support. If you
+  don't need WASM support but have `default_features = false` for other reasons
+  you likely need to re-enable the `tokio` feature ([#1382])
 
 [#1368]: https://github.com/tokio-rs/axum/pull/1368
 [#1371]: https://github.com/tokio-rs/axum/pull/1371
+[#1382]: https://github.com/tokio-rs/axum/pull/1382
 [#1387]: https://github.com/tokio-rs/axum/pull/1387
 [#1389]: https://github.com/tokio-rs/axum/pull/1389
 [#1396]: https://github.com/tokio-rs/axum/pull/1396

axum/Cargo.toml

@@ -12,7 +12,7 @@ readme = "README.md"
 repository = "https://github.com/tokio-rs/axum"
 
 [features]
-default = ["form", "http1", "json", "matched-path", "original-uri", "query", "tower-log"]
+default = ["form", "http1", "json", "matched-path", "original-uri", "query", "tokio", "tower-log"]
 form = ["dep:serde_urlencoded"]
 http1 = ["hyper/http1"]
 http2 = ["hyper/http2"]
@@ -22,8 +22,9 @@ matched-path = []
 multipart = ["dep:multer"]
 original-uri = []
 query = ["dep:serde_urlencoded"]
+tokio = ["dep:tokio", "hyper/server", "hyper/tcp", "tower/make"]
 tower-log = ["tower/log"]
-ws = ["dep:tokio-tungstenite", "dep:sha-1", "dep:base64"]
+ws = ["tokio", "dep:tokio-tungstenite", "dep:sha-1", "dep:base64"]
 
 # Required for intra-doc links to resolve correctly
 __private_docs = ["tower/full", "tower-http/full"]
@@ -36,7 +37,7 @@ bytes = "1.0"
 futures-util = { version = "0.3", default-features = false, features = ["alloc"] }
 http = "0.2.5"
 http-body = "0.4.4"
-hyper = { version = "0.14.14", features = ["server", "tcp", "stream"] }
+hyper = { version = "0.14.14", features = ["stream"] }
 itoa = "1.0.1"
 matchit = "0.6"
 memchr = "2.4.1"
@@ -45,8 +46,7 @@ percent-encoding = "2.1"
 pin-project-lite = "0.2.7"
 serde = "1.0"
 sync_wrapper = "0.1.1"
-tokio = { version = "1", features = ["time"] }
-tower = { version = "0.4.13", default-features = false, features = ["util", "make"] }
+tower = { version = "0.4.13", default-features = false, features = ["util"] }
 tower-http = { version = "0.3.0", features = ["util", "map-response-body"] }
 tower-layer = "0.3"
 tower-service = "0.3"
@@ -60,6 +60,7 @@ serde_json = { version = "1.0", features = ["raw_value"], optional = true }
 serde_path_to_error = { version = "0.1.8", optional = true }
 serde_urlencoded = { version = "0.7", optional = true }
 sha-1 = { version = "0.10", optional = true }
+tokio = { package = "tokio", version = "1.21", features = ["time"], optional = true }
 tokio-tungstenite = { version = "0.17.2", optional = true }
 
 [dev-dependencies]
@@ -70,7 +71,7 @@ quickcheck_macros = "1.0"
 reqwest = { version = "0.11.11", default-features = false, features = ["json", "stream", "multipart"] }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-tokio = { version = "1.6.1", features = ["macros", "rt", "rt-multi-thread", "net", "test-util"] }
+tokio = { package = "tokio", version = "1.21", features = ["macros", "rt", "rt-multi-thread", "net", "test-util"] }
 tokio-stream = "0.1"
 tracing = "0.1"
 uuid = { version = "1.0", features = ["serde", "v4"] }

axum/src/ext_traits/service.rs

@@ -1,4 +1,6 @@
-use crate::{extract::connect_info::IntoMakeServiceWithConnectInfo, routing::IntoMakeService};
+#[cfg(feature = "tokio")]
+use crate::extract::connect_info::IntoMakeServiceWithConnectInfo;
+use crate::routing::IntoMakeService;
 use tower_service::Service;
 
 /// Extension trait that adds additional methods to any [`Service`].
@@ -26,6 +28,7 @@ pub trait ServiceExt<R>: Service<R> + Sized {
     /// ["Rewriting request URI in middleware"]: crate::middleware#rewriting-request-uri-in-middleware
     /// [`Router`]: crate::Router
     /// [`ConnectInfo`]: crate::extract::connect_info::ConnectInfo
+    #[cfg(feature = "tokio")]
     fn into_make_service_with_connect_info<C>(self) -> IntoMakeServiceWithConnectInfo<Self, C>;
 }
 
@@ -37,6 +40,7 @@ where
         IntoMakeService::new(self)
     }
 
+    #[cfg(feature = "tokio")]
     fn into_make_service_with_connect_info<C>(self) -> IntoMakeServiceWithConnectInfo<Self, C> {
         IntoMakeServiceWithConnectInfo::new(self)
     }

axum/src/extract/mod.rs

@@ -2,6 +2,7 @@
 
 use http::header::{self, HeaderMap};
 
+#[cfg(feature = "tokio")]
 pub mod connect_info;
 pub mod path;
 pub mod rejection;
@@ -23,7 +24,6 @@ pub use axum_macros::{FromRequest, FromRequestParts};
 #[doc(inline)]
 #[allow(deprecated)]
 pub use self::{
-    connect_info::ConnectInfo,
     host::Host,
     path::Path,
     raw_query::RawQuery,
@@ -31,6 +31,10 @@ pub use self::{
     state::State,
 };
 
+#[doc(inline)]
+#[cfg(feature = "tokio")]
+pub use self::connect_info::ConnectInfo;
+
 #[doc(no_inline)]
 #[cfg(feature = "json")]
 pub use crate::Json;

axum/src/extract/ws.rs

@@ -72,7 +72,7 @@
 //! If you need to read and write concurrently from a [`WebSocket`] you can use
 //! [`StreamExt::split`]:
 //!
-//! ```
+//! ```rust,no_run
 //! use axum::{Error, extract::ws::{WebSocket, Message}};
 //! use futures::{sink::SinkExt, stream::{StreamExt, SplitSink, SplitStream}};
 //!

axum/src/handler/mod.rs

@@ -35,9 +35,11 @@
 //!
 #![doc = include_str!("../docs/debugging_handler_type_errors.md")]
 
+#[cfg(feature = "tokio")]
+use crate::extract::connect_info::IntoMakeServiceWithConnectInfo;
 use crate::{
     body::Body,
-    extract::{connect_info::IntoMakeServiceWithConnectInfo, FromRequest, FromRequestParts},
+    extract::{FromRequest, FromRequestParts},
     response::{IntoResponse, Response},
     routing::IntoMakeService,
 };
@@ -318,6 +320,7 @@ pub trait HandlerWithoutStateExt<T, B>: Handler<T, (), B> {
     /// See [`WithState::into_make_service_with_connect_info`] for more details.
     ///
     /// [`MakeService`]: tower::make::MakeService
+    #[cfg(feature = "tokio")]
     fn into_make_service_with_connect_info<C>(
         self,
     ) -> IntoMakeServiceWithConnectInfo<IntoService<Self, T, (), B>, C>;
@@ -335,6 +338,7 @@ where
         self.with_state(()).into_make_service()
     }
 
+    #[cfg(feature = "tokio")]
     fn into_make_service_with_connect_info<C>(
         self,
     ) -> IntoMakeServiceWithConnectInfo<IntoService<Self, T, (), B>, C> {

axum/src/handler/with_state.rs

@@ -1,5 +1,7 @@
 use super::{Handler, IntoService};
-use crate::{extract::connect_info::IntoMakeServiceWithConnectInfo, routing::IntoMakeService};
+#[cfg(feature = "tokio")]
+use crate::extract::connect_info::IntoMakeServiceWithConnectInfo;
+use crate::routing::IntoMakeService;
 use http::Request;
 use std::task::{Context, Poll};
 use tower_service::Service;
@@ -95,6 +97,7 @@ impl<H, T, S, B> WithState<H, T, S, B> {
     ///
     /// [`MakeService`]: tower::make::MakeService
     /// [`Router::into_make_service_with_connect_info`]: crate::routing::Router::into_make_service_with_connect_info
+    #[cfg(feature = "tokio")]
     pub fn into_make_service_with_connect_info<C>(
         self,
     ) -> IntoMakeServiceWithConnectInfo<IntoService<H, T, S, B>, C> {

axum/src/lib.rs

@@ -350,6 +350,7 @@
 //! `matched-path` | Enables capturing of every request's router path and the [`MatchedPath`] extractor | Yes
 //! `multipart` | Enables parsing `multipart/form-data` requests with [`Multipart`] | No
 //! `original-uri` | Enables capturing of every request's original URI and the [`OriginalUri`] extractor | Yes
+//! `tokio` | Enables `tokio` as a dependency and `axum::Server`, `SSE` and `extract::connect_info` types. | Yes
 //! `tower-log` | Enables `tower`'s `log` feature | Yes
 //! `ws` | Enables WebSockets support via [`extract::ws`] | No
 //! `form` | Enables the `Form` extractor | Yes
@@ -461,6 +462,7 @@ pub use async_trait::async_trait;
 pub use headers;
 #[doc(no_inline)]
 pub use http;
+#[cfg(feature = "tokio")]
 #[doc(no_inline)]
 pub use hyper::Server;
 

axum/src/response/mod.rs

@@ -5,6 +5,7 @@ use http::{header, HeaderValue};
 
 mod redirect;
 
+#[cfg(feature = "tokio")]
 pub mod sse;
 
 #[doc(no_inline)]
@@ -28,7 +29,11 @@ pub use axum_core::response::{
 };
 
 #[doc(inline)]
-pub use self::{redirect::Redirect, sse::Sse};
+pub use self::redirect::Redirect;
+
+#[doc(inline)]
+#[cfg(feature = "tokio")]
+pub use sse::Sse;
 
 /// An HTML response.
 ///

axum/src/routing/method_routing.rs

@@ -1,10 +1,11 @@
 //! Route to services and handlers based on HTTP methods.
 
 use super::IntoMakeService;
+#[cfg(feature = "tokio")]
+use crate::extract::connect_info::IntoMakeServiceWithConnectInfo;
 use crate::{
     body::{Body, Bytes, HttpBody},
     error_handling::{HandleError, HandleErrorLayer},
-    extract::connect_info::IntoMakeServiceWithConnectInfo,
     handler::{Handler, IntoServiceStateInExtension},
     http::{Method, Request, StatusCode},
     response::Response,
@@ -689,6 +690,7 @@ where
     ///
     /// [`MakeService`]: tower::make::MakeService
     /// [`Router::into_make_service_with_connect_info`]: crate::routing::Router::into_make_service_with_connect_info
+    #[cfg(feature = "tokio")]
     pub fn into_make_service_with_connect_info<C>(self) -> IntoMakeServiceWithConnectInfo<Self, C> {
         IntoMakeServiceWithConnectInfo::new(self)
     }
@@ -1186,6 +1188,7 @@ impl<S, B, E> WithState<S, B, E> {
     /// See [`MethodRouter::into_make_service_with_connect_info`] for more details.
     ///
     /// [`MakeService`]: tower::make::MakeService
+    #[cfg(feature = "tokio")]
     pub fn into_make_service_with_connect_info<C>(self) -> IntoMakeServiceWithConnectInfo<Self, C> {
         IntoMakeServiceWithConnectInfo::new(self)
     }

axum/src/routing/mod.rs

@@ -1,9 +1,10 @@
 //! Routing between [`Service`]s and handlers.
 
 use self::not_found::NotFound;
+#[cfg(feature = "tokio")]
+use crate::extract::connect_info::IntoMakeServiceWithConnectInfo;
 use crate::{
     body::{Body, HttpBody},
-    extract::connect_info::IntoMakeServiceWithConnectInfo,
     handler::{BoxedHandler, Handler},
     util::try_downcast,
     Extension,
@@ -547,6 +548,7 @@ where
     }
 
     #[doc = include_str!("../docs/routing/into_make_service_with_connect_info.md")]
+    #[cfg(feature = "tokio")]
     pub fn into_make_service_with_connect_info<C>(
         self,
     ) -> IntoMakeServiceWithConnectInfo<RouterService<B>, C> {

examples/simple-router-wasm/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "example-simple-router-wasm"
+version = "0.1.0"
+edition = "2018"
+publish = false
+
+[dependencies]
+# `default-features = false` to not depend on tokio features which don't support wasm
+# you can still pull in tokio manually and only add features that tokio supports for wasm
+axum = { path = "../../axum", default-features = false }
+futures-executor = "0.3.21"
+http = "0.2.7"
+tower-service = "0.3.1"

examples/simple-router-wasm/src/main.rs

@@ -0,0 +1,51 @@
+//! Run with
+//!
+//! ```not_rust
+//! cd examples && cargo run -p example-simple-router-wasm
+//! ```
+//!
+//! This example shows what using axum in a wasm context might look like. This example should
+//! always compile with `--target wasm32-unknown-unknown`.
+//!
+//! [`mio`](https://docs.rs/mio/latest/mio/index.html), tokio's IO layer, does not support the
+//! `wasm32-unknown-unknown` target which is why this crate requires `default-features = false`
+//! for axum.
+//!
+//! Most serverless runtimes expect an exported function that takes in a single request and returns
+//! a single response, much like axum's `Handler` trait. In this example, the handler function is
+//! `app` with `main` acting as the serverless runtime which originally receives the request and
+//! calls the app function.
+//!
+//! We can use axum's routing, extractors, tower services, and everything else to implement
+//! our serverless function, even though we are running axum in a wasm context.
+
+use axum::{
+    response::{Html, Response},
+    routing::get,
+    Router,
+};
+use futures_executor::block_on;
+use http::Request;
+use tower_service::Service;
+
+fn main() {
+    let request: Request<String> = Request::builder()
+        .uri("https://serverless.example/api/")
+        .body("Some Body Data".into())
+        .unwrap();
+
+    let response: Response = block_on(app(request));
+    assert_eq!(200, response.status());
+}
+
+#[allow(clippy::let_and_return)]
+async fn app(request: Request<String>) -> Response {
+    let mut router = Router::new().route("/api/", get(index)).into_service();
+
+    let response = router.call(request).await.unwrap();
+    response
+}
+
+async fn index() -> Html<&'static str> {
+    Html("<h1>Hello, World!</h1>")
+}