feat: Add IntoRequest and IntoStreamingRequest traits (#66)

Author: alce

tonic-build/src/client.rs

@@ -99,12 +99,14 @@ fn generate_unary(method: &Method, proto: &str, path: String) -> TokenStream {
     let (request, response) = crate::replace_wellknown(proto, &method);
 
     quote! {
-        pub async fn #ident(&mut self, request: tonic::Request<#request>)
-            -> Result<tonic::Response<#response>, tonic::Status> {
+        pub async fn #ident(
+            &mut self,
+            request: impl tonic::IntoRequest<#request>,
+        ) -> Result<tonic::Response<#response>, tonic::Status> {
            self.ready().await?;
            let codec = tonic::codec::ProstCodec::new();
            let path = http::uri::PathAndQuery::from_static(#path);
-           self.inner.unary(request, path, codec).await
+           self.inner.unary(request.into_request(), path, codec).await
         }
     }
 }
@@ -115,12 +117,14 @@ fn generate_server_streaming(method: &Method, proto: &str, path: String) -> Toke
     let (request, response) = crate::replace_wellknown(proto, &method);
 
     quote! {
-        pub async fn #ident(&mut self, request: tonic::Request<#request>)
-            -> Result<tonic::Response<tonic::codec::Streaming<#response>>, tonic::Status> {
+        pub async fn #ident(
+            &mut self,
+            request: impl tonic::IntoRequest<#request>,
+        ) -> Result<tonic::Response<tonic::codec::Streaming<#response>>, tonic::Status> {
            self.ready().await?;
            let codec = tonic::codec::ProstCodec::new();
            let path = http::uri::PathAndQuery::from_static(#path);
-           self.inner.server_streaming(request, path, codec).await
+           self.inner.server_streaming(request.into_request(), path, codec).await
         }
     }
 }
@@ -131,14 +135,14 @@ fn generate_client_streaming(method: &Method, proto: &str, path: String) -> Toke
     let (request, response) = crate::replace_wellknown(proto, &method);
 
     quote! {
-        pub async fn #ident<S>(&mut self, request: tonic::Request<S>)
-            -> Result<tonic::Response<#response>, tonic::Status>
-            where S: Stream<Item = #request> + Send + 'static,
-        {
+        pub async fn #ident(
+            &mut self,
+            request: impl tonic::IntoStreamingRequest<Message = #request>
+        ) -> Result<tonic::Response<#response>, tonic::Status> {
            self.ready().await?;
            let codec = tonic::codec::ProstCodec::new();
            let path = http::uri::PathAndQuery::from_static(#path);
-           self.inner.client_streaming(request, path, codec).await
+           self.inner.client_streaming(request.into_streaming_request(), path, codec).await
         }
     }
 }
@@ -149,14 +153,14 @@ fn generate_streaming(method: &Method, proto: &str, path: String) -> TokenStream
     let (request, response) = crate::replace_wellknown(proto, &method);
 
     quote! {
-        pub async fn #ident<S>(&mut self, request: tonic::Request<S>)
-            -> Result<tonic::Response<tonic::codec::Streaming<#response>>, tonic::Status>
-            where S: Stream<Item = #request> + Send + 'static,
-        {
+        pub async fn #ident(
+            &mut self,
+            request: impl tonic::IntoStreamingRequest<Message = #request>
+        ) -> Result<tonic::Response<tonic::codec::Streaming<#response>>, tonic::Status> {
            self.ready().await?;
            let codec = tonic::codec::ProstCodec::new();
            let path = http::uri::PathAndQuery::from_static(#path);
-           self.inner.streaming(request, path, codec).await
+           self.inner.streaming(request.into_streaming_request(), path, codec).await
         }
     }
 }

tonic/src/lib.rs

@@ -98,7 +98,7 @@ pub use async_trait::async_trait;
 
 #[doc(inline)]
 pub use codec::Streaming;
-pub use request::Request;
+pub use request::{IntoRequest, IntoStreamingRequest, Request};
 pub use response::Response;
 pub use status::{Code, Status};
 

tonic/src/request.rs

@@ -1,4 +1,5 @@
 use crate::metadata::MetadataMap;
+use futures_core::Stream;
 
 /// A gRPC request and metadata from an RPC call.
 #[derive(Debug)]
@@ -7,6 +8,84 @@ pub struct Request<T> {
     message: T,
 }
 
+/// Trait implemented by RPC request types.
+///
+/// Types implementing this trait can be used as arguments to client RPC
+/// methods without explicitly wrapping them into `tonic::Request`s. The purpose
+/// is to make client calls slightly more convenient to write.
+///
+/// Tonic's code generation and blanket implementations handle this for you,
+/// so it is not necessary to implement this trait directly.
+///
+/// # Example
+///
+/// Given the following gRPC method definition:
+/// ```proto
+/// rpc GetFeature(Point) returns (Feature) {}
+/// ```
+///
+/// we can call `get_feature` in two equivalent ways:
+/// ```rust
+/// # pub struct Point {}
+/// # pub struct Client {}
+/// # impl Client {
+/// #   fn get_feature(&self, r: impl tonic::IntoRequest<Point>) {}
+/// # }
+/// # let client = Client {};
+/// use tonic::Request;
+///
+/// client.get_feature(Point {});
+/// client.get_feature(Request::new(Point {}));
+/// ```
+pub trait IntoRequest<T>: sealed::Sealed {
+    /// Wrap the input message `T` in a `tonic::Request`
+    fn into_request(self) -> Request<T>;
+}
+
+/// Trait implemented by RPC streaming request types.
+///
+/// Types implementing this trait can be used as arguments to client streaming
+/// RPC methods without explicitly wrapping them into `tonic::Request`s. The
+/// purpose is to make client calls slightly more convenient to write.
+///
+/// Tonic's code generation and blanket implementations handle this for you,
+/// so it is not necessary to implement this trait directly.
+///
+/// # Example
+///
+/// Given the following gRPC service method definition:
+/// ```proto
+/// rpc RecordRoute(stream Point) returns (RouteSummary) {}
+/// ```
+/// we can call `record_route` in two equivalent ways:
+///
+/// ```rust
+/// # #[derive(Clone)]
+/// # pub struct Point {};
+/// # pub struct Client {};
+/// # impl Client {
+/// #   fn record_route(&self, r: impl tonic::IntoStreamingRequest<Message = Point>) {}
+/// # }
+/// # let client = Client {};
+/// use tonic::Request;
+/// use futures_util::stream;
+///
+/// let messages = vec![Point {}, Point {}];
+///
+/// client.record_route(Request::new(stream::iter(messages.clone())));
+/// client.record_route(stream::iter(messages));
+/// ```
+pub trait IntoStreamingRequest: sealed::Sealed {
+    /// The RPC request stream type
+    type Stream: Stream<Item = Self::Message> + Send + 'static;
+
+    /// The RPC request type
+    type Message;
+
+    /// Wrap the stream of messages in a `tonic::Request`
+    fn into_streaming_request(self) -> Request<Self::Stream>;
+}
+
 impl<T> Request<T> {
     /// Create a new gRPC request.
     ///
@@ -88,3 +167,45 @@ impl<T> Request<T> {
         }
     }
 }
+
+impl<T> IntoRequest<T> for T {
+    fn into_request(self) -> Request<Self> {
+        Request::new(self)
+    }
+}
+
+impl<T> IntoRequest<T> for Request<T> {
+    fn into_request(self) -> Request<T> {
+        self
+    }
+}
+
+impl<T> IntoStreamingRequest for T
+where
+    T: Stream + Send + 'static,
+{
+    type Stream = T;
+    type Message = T::Item;
+
+    fn into_streaming_request(self) -> Request<Self> {
+        Request::new(self)
+    }
+}
+
+impl<T> IntoStreamingRequest for Request<T>
+where
+    T: Stream + Send + 'static,
+{
+    type Stream = T;
+    type Message = T::Item;
+
+    fn into_streaming_request(self) -> Self {
+        self
+    }
+}
+
+impl<T> sealed::Sealed for T {}
+
+mod sealed {
+    pub trait Sealed {}
+}