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

tonic/Cargo.toml

@@ -26,6 +26,15 @@ keywords = ["rpc", "grpc", "async", "futures", "protobuf"]
 default = ["transport", "codegen", "prost"]
 codegen = ["async-trait"]
 transport = [
+    "hyper/default",
+    "hyper/stream",
+    "tokio",
+    "tower",
+    "tower-balance",
+    "tower-load",
+    "tracing-futures",
+]
+client = [
     "hyper",
     "tokio",
     "tower",
@@ -64,8 +73,8 @@ prost-derive = { version = "0.6", optional = true }
 async-trait = { version = "0.1.13", optional = true }
 
 # transport
-hyper = { version = "0.13.4", features = ["stream"], optional = true }
-tokio = { version = "0.2.13", features = ["tcp"], optional = true }
+hyper = { version = "0.13.4", default-features = false, optional = true }
+tokio = { version = "0.2.13", optional = true }
 tower = { version = "0.3", optional = true}
 tower-make = { version = "0.3", features = ["connect"] }
 tower-balance =  { version = "0.3", optional = true }
@@ -76,6 +85,9 @@ tracing-futures = { version = "0.2", optional = true }
 tokio-rustls = { version = "0.14", optional = true }
 rustls-native-certs = { version = "0.4", optional = true }
 
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+wasm-bindgen-futures = "0.4.18"
+
 [dev-dependencies]
 tokio = { version = "0.2", features = ["rt-core", "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

@@ -39,6 +39,7 @@ 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>,
@@ -203,6 +204,7 @@ 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);
@@ -223,6 +225,7 @@ 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

@@ -108,6 +108,7 @@ 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, mut tx) = Self::balance_channel(DEFAULT_BUFFER_SIZE);
         list.for_each(|endpoint| {
@@ -121,6 +122,7 @@ 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,

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};
@@ -105,5 +124,6 @@ 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

@@ -1,29 +1,12 @@
+use super::super::Connected;
 #[cfg(feature = "tls")]
 use super::TlsStream;
-use crate::transport::Certificate;
 use hyper::server::conn::AddrStream;
 use std::net::SocketAddr;
 use tokio::net::TcpStream;
 #[cfg(feature = "tls")]
 use tokio_rustls::rustls::Session;
 
-/// 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

@@ -28,6 +28,22 @@ 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 struct Executor;
+
+    impl hyper::rt::Executor<BoxSendFuture> for Executor {
+        fn execute(&self, fut: BoxSendFuture) {
+            wasm_bindgen_futures::spawn_local(fut)
+        }
+    }
+}
+
 impl Connection {
     pub(crate) fn new<C>(
         connector: C,
@@ -44,16 +60,21 @@ impl Connection {
             .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)
+            // .http2_keep_alive_interval(endpoint.http2_keep_alive_interval)
             .clone();
 
-        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);
-        }
+        // 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);
+        // }
 
         let settings = settings.clone();
 

tonic/src/transport/service/discover.rs

@@ -29,6 +29,7 @@ impl<K: Hash + Eq + Clone> DynamicServiceStream<K> {
     }
 }
 
+#[cfg(feature = "transport")]
 impl<K: Hash + Eq + Clone> Discover for DynamicServiceStream<K> {
     type Key = K;
     type Service = Connection;

tonic/src/transport/service/io.rs

@@ -1,4 +1,4 @@
-use crate::transport::{server::Connected, Certificate};
+use crate::transport::{Certificate, Connected};
 use hyper::client::connect::{Connected as HyperConnected, Connection};
 use std::io;
 use std::net::SocketAddr;