http3: minor simplification of panic handling logic (#4942)

http3/server.go

@@ -684,7 +684,7 @@ func (s *Server) handleRequest(conn *connection, str quic.Stream, datagrams *dat
 				if logger == nil {
 					logger = slog.Default()
 				}
-				logger.Error("http: panic serving", "arg", p, "trace", string(buf))
+				logger.Error("http3: panic serving", "arg", p, "trace", string(buf))
 			}
 		}()
 		handler.ServeHTTP(r, req)
@@ -694,8 +694,13 @@ func (s *Server) handleRequest(conn *connection, str quic.Stream, datagrams *dat
 		return
 	}
 
-	// only write response when there is no panic
+	// abort the stream when there is a panic
-	if !panicked {
+	if panicked {
+		str.CancelRead(quic.StreamErrorCode(ErrCodeInternalError))
+		str.CancelWrite(quic.StreamErrorCode(ErrCodeInternalError))
+		return
+	}
+
 	// response not written to the client yet, set Content-Length
 	if !r.headerWritten {
 		if _, haveCL := r.header["Content-Length"]; !haveCL {
@@ -704,18 +709,9 @@ func (s *Server) handleRequest(conn *connection, str quic.Stream, datagrams *dat
 	}
 	r.Flush()
 	r.flushTrailers()
-	}
-
-	// abort the stream when there is a panic
-	if panicked {
-		str.CancelRead(quic.StreamErrorCode(ErrCodeInternalError))
-		str.CancelWrite(quic.StreamErrorCode(ErrCodeInternalError))
-		return
-	}
 
 	// If the EOF was read by the handler, CancelRead() is a no-op.
 	str.CancelRead(quic.StreamErrorCode(ErrCodeNoError))
-
 	str.Close()
 }
 

http3/server_test.go

@@ -314,7 +314,7 @@ var _ = Describe("Server", func() {
 
 			s.handleRequest(conn, str, nil, qpackDecoder)
 			Expect(responseBuf.Bytes()).To(HaveLen(0))
-			Expect(logBuf.String()).To(ContainSubstring("http: panic serving"))
+			Expect(logBuf.String()).To(ContainSubstring("http3: panic serving"))
 			Expect(logBuf.String()).To(ContainSubstring("foobar"))
 		})