feat(transport): Add channel feature flag (#960)

tonic/Cargo.toml

@@ -33,6 +33,9 @@ tls-roots-common = ["tls"]
 tls-webpki-roots = ["tls-roots-common", "webpki-roots"]
 transport = [
   "axum",
+  "channel"
+]
+channel = [
   "h2",
   "hyper",
   "tokio",

tonic/src/lib.rs

@@ -17,7 +17,9 @@
 //! # Feature Flags
 //!
 //! - `transport`: Enables the fully featured, batteries included client and server
-//! implementation based on [`hyper`], [`tower`] and [`tokio`]. Enabled by default.
+//!     implementation based on [`hyper`], [`tower`] and [`tokio`]. Enabled by default.
+//! - `channel`: Enables just the full featured channel/client portion of the `transport`
+//!     feature.
 //! - `codegen`: Enables all the required exports and optional dependencies required
 //! for [`tonic-build`]. Enabled by default.
 //! - `tls`: Enables the `rustls` based TLS options for the `transport` feature. Not

tonic/src/transport/mod.rs

@@ -94,6 +94,8 @@ mod service;
 mod tls;
 
 #[doc(inline)]
+#[cfg(feature = "channel")]
+#[cfg_attr(docsrs, doc(cfg(feature = "channel")))]
 pub use self::channel::{Channel, Endpoint};
 pub use self::error::Error;
 #[doc(inline)]