fix(codec): Fix streaming reponses w/ many status (#689)

Closes #681

tonic/src/codec/decode.rs

@@ -258,7 +258,11 @@ impl<T> Stream for Streaming<T> {
             match ready!(Pin::new(&mut self.body).poll_trailers(cx)) {
                 Ok(trailer) => {
                     if let Err(e) = crate::status::infer_grpc_status(trailer.as_ref(), status) {
-                        return Some(Err(e)).into();
+                        if let Some(e) = e {
+                            return Some(Err(e)).into();
+                        } else {
+                            return Poll::Ready(None);
+                        }
                     } else {
                         self.trailers = trailer.map(MetadataMap::from_headers);
                     }

tonic/src/codec/encode.rs

@@ -88,6 +88,7 @@ pub(crate) struct EncodeBody<S> {
     inner: S,
     error: Option<Status>,
     role: Role,
+    is_end_stream: bool,
 }
 
 impl<S> EncodeBody<S>
@@ -99,6 +100,7 @@ where
             inner,
             error: None,
             role: Role::Client,
+            is_end_stream: false,
         }
     }
 
@@ -107,6 +109,7 @@ where
             inner,
             error: None,
             role: Role::Server,
+            is_end_stream: false,
         }
     }
 }
@@ -119,7 +122,7 @@ where
     type Error = Status;
 
     fn is_end_stream(&self) -> bool {
-        false
+        self.is_end_stream
     }
 
     fn poll_data(
@@ -148,7 +151,13 @@ where
             Role::Client => Poll::Ready(Ok(None)),
             Role::Server => {
                 let self_proj = self.project();
+
+                if *self_proj.is_end_stream {
+                    return Poll::Ready(Ok(None));
+                }
+
                 let status = if let Some(status) = self_proj.error.take() {
+                    *self_proj.is_end_stream = true;
                     status
                 } else {
                     Status::new(Code::Ok, "")

tonic/src/status.rs

@@ -657,13 +657,13 @@ impl Error for Status {
 pub(crate) fn infer_grpc_status(
     trailers: Option<&HeaderMap>,
     status_code: http::StatusCode,
-) -> Result<(), Status> {
+) -> Result<(), Option<Status>> {
     if let Some(trailers) = trailers {
         if let Some(status) = Status::from_header_map(&trailers) {
             if status.code() == Code::Ok {
                 return Ok(());
             } else {
-                return Err(status);
+                return Err(status.into());
             }
         }
     }
@@ -678,6 +678,13 @@ pub(crate) fn infer_grpc_status(
         | http::StatusCode::BAD_GATEWAY
         | http::StatusCode::SERVICE_UNAVAILABLE
         | http::StatusCode::GATEWAY_TIMEOUT => Code::Unavailable,
+        // We got a 200 but no trailers, we can infer that this request is finished.
+        //
+        // This can happen when a streaming response sends two Status but
+        // gRPC requires that we end the stream after the first status.
+        //
+        // https://github.com/hyperium/tonic/issues/681
+        http::StatusCode::OK => return Err(None),
         _ => Code::Unknown,
     };
 
@@ -686,7 +693,7 @@ pub(crate) fn infer_grpc_status(
         status_code.as_u16(),
     );
     let status = Status::new(code, msg);
-    Err(status)
+    Err(status.into())
 }
 
 // ===== impl Code =====