Quick and dirty patch to compile client-only transport on wasm32.

Author: boxdot

tonic/Cargo.toml

@@ -27,12 +27,20 @@ default = ["transport", "codegen", "prost"]
 codegen = ["async-trait"]
 transport = [
     "h2",
-    "hyper",
-    "tokio",
+    "hyper/full",
+    "tokio/net",
     "tower",
+    "tower/balance",
     "tracing-futures",
     "tokio/macros"
 ]
+client = [
+    "h2",
+    "hyper/client",
+    "hyper/http2",
+    "tokio",
+    "tower",
+]
 tls = ["transport", "tokio-rustls"]
 tls-roots = ["tls", "rustls-native-certs"]
 prost = ["prost1", "prost-derive"]
@@ -65,16 +73,19 @@ async-trait = { version = "0.1.13", optional = true }
 
 # transport
 h2    = { version = "0.3", optional = true }
-hyper = { version = "0.14.2", features = ["full"], optional = true }
-tokio = { version = "1.0.1", features = ["net"], optional = true }
+hyper = { version = "0.14.2", default-features = false, optional = true }
+tokio = { version = "1.0.1", default-features = false, optional = true }
 tokio-stream = "0.1"
-tower = { version = "0.4", features = ["balance", "buffer", "discover", "limit", "load", "make", "timeout", "util"], optional = true}
+tower = { version = "0.4", features = ["buffer", "discover", "limit", "load", "make", "timeout", "util"], optional = true}
 tracing-futures = { version = "0.2", optional = true }
 
 # rustls
 tokio-rustls = { version = "0.22", optional = true }
 rustls-native-certs = { version = "0.5", optional = true }
 
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+wasm-bindgen-futures = "0.4.18"
+
 [dev-dependencies]
 tokio = { version = "1.0", features = ["rt", "macros"] }
 static_assertions = "1.0"

tonic/src/lib.rs

@@ -82,7 +82,7 @@ pub mod codec;
 pub mod metadata;
 pub mod server;
 
-#[cfg(feature = "transport")]
+#[cfg(any(feature = "transport", feature = "client"))]
 #[cfg_attr(docsrs, doc(cfg(feature = "transport")))]
 pub mod transport;
 

tonic/src/request.rs

@@ -1,10 +1,10 @@
 use crate::metadata::MetadataMap;
-#[cfg(feature = "transport")]
+#[cfg(any(feature = "transport", feature = "client"))]
 use crate::transport::Certificate;
 use futures_core::Stream;
 use http::Extensions;
 use std::net::SocketAddr;
-#[cfg(feature = "transport")]
+#[cfg(any(feature = "transport", feature = "client"))]
 use std::sync::Arc;
 
 /// A gRPC request and metadata from an RPC call.
@@ -18,7 +18,7 @@ pub struct Request<T> {
 #[derive(Clone)]
 pub(crate) struct ConnectionInfo {
     pub(crate) remote_addr: Option<SocketAddr>,
-    #[cfg(feature = "transport")]
+    #[cfg(any(feature = "transport", feature = "client"))]
     pub(crate) peer_certs: Option<Arc<Vec<Certificate>>>,
 }
 

tonic/src/transport/channel/endpoint.rs

@@ -43,6 +43,7 @@ impl Endpoint {
     // FIXME: determine if we want to expose this or not. This is really
     // just used in codegen for a shortcut.
     #[doc(hidden)]
+    #[cfg(feature = "transport")]
     pub fn new<D>(dst: D) -> Result<Self, Error>
     where
         D: TryInto<Self>,
@@ -231,6 +232,7 @@ impl Endpoint {
     }
 
     /// Create a channel from this config.
+    #[cfg(feature = "transport")]
     pub async fn connect(&self) -> Result<Channel, Error> {
         let mut http = hyper::client::connect::HttpConnector::new();
         http.enforce_http(false);
@@ -250,6 +252,7 @@ impl Endpoint {
     ///
     /// The channel returned by this method does not attempt to connect to the endpoint until first
     /// use.
+    #[cfg(feature = "transport")]
     pub fn connect_lazy(&self) -> Result<Channel, Error> {
         let mut http = hyper::client::connect::HttpConnector::new();
         http.enforce_http(false);

tonic/src/transport/channel/mod.rs

@@ -9,30 +9,35 @@ pub use endpoint::Endpoint;
 #[cfg(feature = "tls")]
 pub use tls::ClientTlsConfig;
 
-use super::service::{Connection, DynamicServiceStream};
+use super::service::Connection;
+#[cfg(feature = "transport")]
+use super::service::DynamicServiceStream;
 use crate::body::BoxBody;
 use bytes::Bytes;
 use http::{
     uri::{InvalidUri, Uri},
     Request, Response,
 };
 use hyper::client::connect::Connection as HyperConnection;
+#[cfg(feature = "transport")]
+use std::hash::Hash;
 use std::{
     fmt,
     future::Future,
-    hash::Hash,
     pin::Pin,
     task::{Context, Poll},
 };
-use tokio::{
-    io::{AsyncRead, AsyncWrite},
-    sync::mpsc::{channel, Sender},
-};
 
+use tokio::io::{AsyncRead, AsyncWrite};
+#[cfg(feature = "transport")]
+use tokio::sync::mpsc::{channel, Sender};
+
+#[cfg(feature = "transport")]
 use tower::balance::p2c::Balance;
+#[cfg(feature = "transport")]
+use tower::discover::{Change, Discover};
 use tower::{
     buffer::{self, Buffer},
-    discover::{Change, Discover},
     util::{BoxService, Either},
     Service,
 };
@@ -108,6 +113,7 @@ impl Channel {
     ///
     /// This creates a [`Channel`] that will load balance accross all the
     /// provided endpoints.
+    #[cfg(feature = "transport")]
     pub fn balance_list(list: impl Iterator<Item = Endpoint>) -> Self {
         let (channel, tx) = Self::balance_channel(DEFAULT_BUFFER_SIZE);
         list.for_each(|endpoint| {
@@ -121,6 +127,7 @@ impl Channel {
     /// Balance a list of [`Endpoint`]'s.
     ///
     /// This creates a [`Channel`] that will listen to a stream of change events and will add or remove provided endpoints.
+    #[cfg(feature = "transport")]
     pub fn balance_channel<K>(capacity: usize) -> (Self, Sender<Change<K, Endpoint>>)
     where
         K: Hash + Eq + Send + Clone + 'static,
@@ -130,6 +137,7 @@ impl Channel {
         (Self::balance(list, DEFAULT_BUFFER_SIZE), tx)
     }
 
+    #[cfg(feature = "transport")]
     pub(crate) fn new<C>(connector: C, endpoint: Endpoint) -> Self
     where
         C: Service<Uri> + Send + 'static,
@@ -162,6 +170,7 @@ impl Channel {
         Ok(Channel { svc })
     }
 
+    #[cfg(feature = "transport")]
     pub(crate) fn balance<D>(discover: D, buffer_size: usize) -> Self
     where
         D: Discover<Service = Connection> + Unpin + Send + 'static,

tonic/src/transport/mod.rs

@@ -87,15 +87,34 @@
 //! [rustls]: https://docs.rs/rustls/0.16.0/rustls/
 
 pub mod channel;
+#[cfg(feature = "transport")]
 pub mod server;
 
+/// Trait that connected IO resources implement.
+///
+/// The goal for this trait is to allow users to implement
+/// custom IO types that can still provide the same connection
+/// metadata.
+pub trait Connected {
+    /// Return the remote address this IO resource is connected too.
+    fn remote_addr(&self) -> Option<std::net::SocketAddr> {
+        None
+    }
+
+    /// Return the set of connected peer TLS certificates.
+    fn peer_certs(&self) -> Option<Vec<Certificate>> {
+        None
+    }
+}
+
 mod error;
 mod service;
 mod tls;
 
 #[doc(inline)]
 pub use self::channel::{Channel, Endpoint};
 pub use self::error::Error;
+#[cfg(feature = "transport")]
 #[doc(inline)]
 pub use self::server::{NamedService, Server};
 pub use self::tls::{Certificate, Identity};
@@ -105,6 +124,7 @@ pub use hyper::{Body, Uri};
 #[cfg_attr(docsrs, doc(cfg(feature = "tls")))]
 pub use self::channel::ClientTlsConfig;
 #[cfg(feature = "tls")]
+#[cfg(feature = "transport")]
 #[cfg_attr(docsrs, doc(cfg(feature = "tls")))]
 pub use self::server::ServerTlsConfig;
 

tonic/src/transport/server/conn.rs

@@ -1,27 +1,12 @@
+#[cfg(feature = "tls")]
 use crate::transport::Certificate;
+use crate::transport::Connected;
 use hyper::server::conn::AddrStream;
 use std::net::SocketAddr;
 use tokio::net::TcpStream;
 #[cfg(feature = "tls")]
 use tokio_rustls::{rustls::Session, server::TlsStream};
 
-/// Trait that connected IO resources implement.
-///
-/// The goal for this trait is to allow users to implement
-/// custom IO types that can still provide the same connection
-/// metadata.
-pub trait Connected {
-    /// Return the remote address this IO resource is connected too.
-    fn remote_addr(&self) -> Option<SocketAddr> {
-        None
-    }
-
-    /// Return the set of connected peer TLS certificates.
-    fn peer_certs(&self) -> Option<Vec<Certificate>> {
-        None
-    }
-}
-
 impl Connected for AddrStream {
     fn remote_addr(&self) -> Option<SocketAddr> {
         Some(self.remote_addr())

tonic/src/transport/server/mod.rs

@@ -6,7 +6,7 @@ mod incoming;
 #[cfg_attr(docsrs, doc(cfg(feature = "tls")))]
 mod tls;
 
-pub use conn::Connected;
+pub use super::Connected;
 #[cfg(feature = "tls")]
 pub use tls::ServerTlsConfig;
 

tonic/src/transport/service/connection.rs

@@ -27,6 +27,22 @@ pub(crate) struct Connection {
     inner: BoxService<Request, Response, crate::Error>,
 }
 
+#[cfg(target_arch = "wasm32")]
+mod wasm {
+    use std::future::Future;
+    use std::pin::Pin;
+
+    type BoxSendFuture = Pin<Box<dyn Future<Output = ()> + Send>>;
+
+    pub(crate) struct Executor;
+
+    impl hyper::rt::Executor<BoxSendFuture> for Executor {
+        fn execute(&self, fut: BoxSendFuture) {
+            wasm_bindgen_futures::spawn_local(fut)
+        }
+    }
+}
+
 impl Connection {
     fn new<C>(connector: C, endpoint: Endpoint, is_lazy: bool) -> Self
     where
@@ -35,21 +51,29 @@ impl Connection {
         C::Future: Unpin + Send,
         C::Response: AsyncRead + AsyncWrite + HyperConnection + Unpin + Send + 'static,
     {
-        let mut settings = Builder::new()
-            .http2_initial_stream_window_size(endpoint.init_stream_window_size)
-            .http2_initial_connection_window_size(endpoint.init_connection_window_size)
-            .http2_only(true)
-            .http2_keep_alive_interval(endpoint.http2_keep_alive_interval)
-            .clone();
+        let mut settings = Builder::new();
 
-        if let Some(val) = endpoint.http2_keep_alive_timeout {
-            settings.http2_keep_alive_timeout(val);
+        #[cfg(target_arch = "wasm32")]
+        {
+            settings.executor(wasm::Executor);
         }
-
-        if let Some(val) = endpoint.http2_keep_alive_while_idle {
-            settings.http2_keep_alive_while_idle(val);
+        #[cfg(feature = "transport")]
+        {
+            settings.http2_keep_alive_interval(endpoint.http2_keep_alive_interval);
+            if let Some(val) = endpoint.http2_keep_alive_timeout {
+                settings.http2_keep_alive_timeout(val);
+            }
+
+            if let Some(val) = endpoint.http2_keep_alive_while_idle {
+                settings.http2_keep_alive_while_idle(val);
+            }
         }
 
+        settings
+            .http2_initial_stream_window_size(endpoint.init_stream_window_size)
+            .http2_initial_connection_window_size(endpoint.init_connection_window_size)
+            .http2_only(true);
+
         let stack = ServiceBuilder::new()
             .layer_fn(|s| AddOrigin::new(s, endpoint.uri.clone()))
             .layer_fn(|s| UserAgent::new(s, endpoint.user_agent.clone()))
@@ -78,6 +102,7 @@ impl Connection {
         Self::new(connector, endpoint, false).ready_oneshot().await
     }
 
+    #[cfg(feature = "transport")]
     pub(crate) fn lazy<C>(connector: C, endpoint: Endpoint) -> Self
     where
         C: Service<Uri> + Send + 'static,

tonic/src/transport/service/io.rs

@@ -1,6 +1,9 @@
-use crate::transport::{server::Connected, Certificate};
+#[cfg(feature = "transport")]
+use crate::transport::Certificate;
+use crate::transport::Connected;
 use hyper::client::connect::{Connected as HyperConnected, Connection};
 use std::io;
+#[cfg(feature = "transport")]
 use std::net::SocketAddr;
 use std::pin::Pin;
 use std::task::{Context, Poll};
@@ -61,14 +64,17 @@ pub(in crate::transport) trait ConnectedIo: Io + Connected {}
 
 impl<T> ConnectedIo for T where T: Io + Connected {}
 
+#[cfg(feature = "transport")]
 pub(crate) struct ServerIo(Pin<Box<dyn ConnectedIo>>);
 
+#[cfg(feature = "transport")]
 impl ServerIo {
     pub(in crate::transport) fn new<I: ConnectedIo>(io: I) -> Self {
         ServerIo(Box::pin(io))
     }
 }
 
+#[cfg(feature = "transport")]
 impl Connected for ServerIo {
     fn remote_addr(&self) -> Option<SocketAddr> {
         (&*self.0).remote_addr()
@@ -79,6 +85,7 @@ impl Connected for ServerIo {
     }
 }
 
+#[cfg(feature = "transport")]
 impl AsyncRead for ServerIo {
     fn poll_read(
         mut self: Pin<&mut Self>,
@@ -89,6 +96,7 @@ impl AsyncRead for ServerIo {
     }
 }
 
+#[cfg(feature = "transport")]
 impl AsyncWrite for ServerIo {
     fn poll_write(
         mut self: Pin<&mut Self>,