fix(codec): Remove custom content-type (#104)

This removes custom content-types in favor of
just using `application/grpc`. There is some
confusion around the specification but most
grpc implementations ignore the `+` and
anything after.

tonic/benches/benchmarks/compiled_protos/helloworld.rs

@@ -55,7 +55,7 @@ pub mod client {
             request: tonic::Request<super::HelloRequest>,
         ) -> Result<tonic::Response<super::HelloReply>, tonic::Status> {
             self.ready().await?;
-            let codec = tonic::codec::ProstCodec::new();
+            let codec = tonic::codec::ProstCodec::default();
             let path = http::uri::PathAndQuery::from_static("/helloworld.Greeter/SayHello");
             self.inner.unary(request, path, codec).await
         }
@@ -146,7 +146,7 @@ pub mod server {
                     let inner = self.inner.clone();
                     let fut = async move {
                         let method = SayHello(inner);
-                        let codec = tonic::codec::ProstCodec::new();
+                        let codec = tonic::codec::ProstCodec::default();
                         let mut grpc = tonic::server::Grpc::new(codec);
                         let res = grpc.unary(method, req).await;
                         Ok(res)

tonic/src/client/grpc.rs

@@ -156,10 +156,9 @@ impl<T> Grpc<T> {
             .insert(TE, HeaderValue::from_static("trailers"));
 
         // Set the content type
-        let content_type = <C as Codec>::CONTENT_TYPE;
         request
             .headers_mut()
-            .insert(CONTENT_TYPE, HeaderValue::from_static(content_type));
+            .insert(CONTENT_TYPE, HeaderValue::from_static("application/grpc"));
 
         let response = self
             .inner

tonic/src/codec/mod.rs

@@ -21,7 +21,7 @@ pub use tokio_codec::{Decoder, Encoder};
 use crate::Status;
 
 /// Trait that knows how to encode and decode gRPC messages.
-pub trait Codec {
+pub trait Codec: Default {
     /// The encodable message.
     type Encode: Send + 'static;
     /// The decodable message.
@@ -32,13 +32,6 @@ pub trait Codec {
     /// The encoder that can decode a message.
     type Decoder: Decoder<Item = Self::Decode, Error = Status> + Send + 'static;
 
-    /// The content type of this codec.
-    ///
-    /// This should follow the `Content-Type` definition [here].
-    ///
-    /// [here]: https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests
-    const CONTENT_TYPE: &'static str;
-
     /// Fetch the encoder.
     fn encoder(&mut self) -> Self::Encoder;
     /// Fetch the decoder.

tonic/src/codec/prost.rs

@@ -10,9 +10,8 @@ pub struct ProstCodec<T, U> {
     _pd: PhantomData<(T, U)>,
 }
 
-impl<T, U> ProstCodec<T, U> {
-    /// Create a new codec that knows how to encode `T` and decode `U`.
-    pub fn new() -> Self {
+impl<T, U> Default for ProstCodec<T, U> {
+    fn default() -> Self {
         Self { _pd: PhantomData }
     }
 }
@@ -28,8 +27,6 @@ where
     type Encoder = ProstEncoder<T>;
     type Decoder = ProstDecoder<U>;
 
-    const CONTENT_TYPE: &'static str = "application/grpc+proto";
-
     fn encoder(&mut self) -> Self::Encoder {
         ProstEncoder(PhantomData)
     }

tonic/src/server/grpc.rs

@@ -179,7 +179,7 @@ where
                 // Set the content type
                 parts.headers.insert(
                     http::header::CONTENT_TYPE,
-                    http::header::HeaderValue::from_static(T::CONTENT_TYPE),
+                    http::header::HeaderValue::from_static("application/grpc"),
                 );
 
                 let body = encode_server(self.codec.encoder(), body.into_stream());
@@ -191,7 +191,7 @@ where
 
                 parts.headers.insert(
                     http::header::CONTENT_TYPE,
-                    http::header::HeaderValue::from_static(T::CONTENT_TYPE),
+                    http::header::HeaderValue::from_static("application/grpc"),
                 );
 
                 status.add_header(&mut parts.headers).unwrap();