Add debug assertions check to streaming (#635)

This is used by Cargo Lambda's local server to control req/response.

Signed-off-by: David Calavera <[email protected]>

Author: calavera

lambda-runtime/src/streaming.rs

@@ -108,6 +108,14 @@ where
             let event = next_event_response?;
             let (parts, body) = event.into_parts();
 
+            #[cfg(debug_assertions)]
+            if parts.status == http::StatusCode::NO_CONTENT {
+                // Ignore the event if the status code is 204.
+                // This is a way to keep the runtime alive when
+                // there are no events pending to be processed.
+                continue;
+            }
+
             let ctx: Context = Context::try_from(parts.headers)?;
             let ctx: Context = ctx.with_config(config);
             let request_id = &ctx.request_id.clone();
@@ -128,6 +136,12 @@ where
                 let body = hyper::body::to_bytes(body).await?;
                 trace!("incoming request payload - {}", std::str::from_utf8(&body)?);
 
+                #[cfg(debug_assertions)]
+                if parts.status.is_server_error() {
+                    error!("Lambda Runtime server returned an unexpected error");
+                    return Err(parts.status.to_string().into());
+                }
+
                 let body = match serde_json::from_slice(&body) {
                     Ok(body) => body,
                     Err(err) => {