serve: fix handle not isClosingError err to use event.Error

Author: zchee

serve.go

@@ -1,5 +1,5 @@
-// SPDX-License-Identifier: BSD-3-Clause
 // SPDX-FileCopyrightText: Copyright 2021 The Go Language Server Authors
+// SPDX-License-Identifier: BSD-3-Clause
 
 package jsonrpc2
 
@@ -11,23 +11,27 @@ import (
 	"net"
 	"os"
 	"time"
+
+	"go.lsp.dev/pkg/event"
 )
 
 // NOTE: This file provides an experimental API for serving multiple remote
 // jsonrpc2 clients over the network. For now, it is intentionally similar to
 // net/http, but that may change in the future as we figure out the correct
 // semantics.
 
-// A StreamServer is used to serve incoming jsonrpc2 clients communicating over
+// StreamServer is used to serve incoming jsonrpc2 clients communicating over
 // a newly created connection.
 type StreamServer interface {
 	ServeStream(context.Context, Conn) error
 }
 
-// The ServerFunc type is an adapter that implements the StreamServer interface
+// ServerFunc is an adapter that implements the StreamServer interface
 // using an ordinary function.
 type ServerFunc func(context.Context, Conn) error
 
+// ServeStream implements StreamServer.
+//
 // ServeStream calls f(ctx, s).
 func (f ServerFunc) ServeStream(ctx context.Context, c Conn) error {
 	return f(ctx, c)
@@ -43,18 +47,21 @@ func HandlerServer(h Handler) StreamServer {
 	})
 }
 
-// ListenAndServe starts an jsonrpc2 server on the given address.  If
-// idleTimeout is non-zero, ListenAndServe exits after there are no clients for
+// ListenAndServe starts an jsonrpc2 server on the given address.
+//
+// If idleTimeout is non-zero, ListenAndServe exits after there are no clients for
 // this duration, otherwise it exits only on error.
 func ListenAndServe(ctx context.Context, network, addr string, server StreamServer, idleTimeout time.Duration) error {
 	ln, err := net.Listen(network, addr)
 	if err != nil {
 		return fmt.Errorf("failed to listen %s:%s: %w", network, addr, err)
 	}
 	defer ln.Close()
+
 	if network == "unix" {
 		defer os.Remove(addr)
 	}
+
 	return Serve(ctx, ln, server, idleTimeout)
 }
 
@@ -64,6 +71,7 @@ func ListenAndServe(ctx context.Context, network, addr string, server StreamServ
 func Serve(ctx context.Context, ln net.Listener, server StreamServer, idleTimeout time.Duration) error {
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()
+
 	// Max duration: ~290 years; surely that's long enough.
 	const forever = 1<<63 - 1
 	if idleTimeout <= 0 {
@@ -85,6 +93,7 @@ func Serve(ctx context.Context, ln net.Listener, server StreamServer, idleTimeou
 				}
 				return
 			}
+
 			newConns <- nc
 		}
 	}()
@@ -101,36 +110,45 @@ func Serve(ctx context.Context, ln net.Listener, server StreamServer, idleTimeou
 				closedConns <- server.ServeStream(ctx, conn)
 				stream.Close()
 			}()
+
 		case err := <-doneListening:
 			return err
+
 		case err := <-closedConns:
 			if !isClosingError(err) {
-				return err
+				event.Error(ctx, "closed a connection", err)
 			}
+
 			activeConns--
 			if activeConns == 0 {
 				connTimer.Reset(idleTimeout)
 			}
+
 		case <-connTimer.C:
 			return ErrIdleTimeout
+
 		case <-ctx.Done():
 			return ctx.Err()
 		}
 	}
 }
 
-// isClosingError reports if the error occurs normally during the process of
-// closing a network connection. It uses imperfect heuristics that err on the
-// side of false negatives, and should not be used for anything critical.
+// isClosingError reports whether the error occurs normally during the process of
+// closing a network connection.
+//
+// It uses imperfect heuristics that err on the side of false negatives,
+// and should not be used for anything critical.
 func isClosingError(err error) bool {
 	if errors.Is(err, io.EOF) {
 		return true
 	}
+
 	// Per https://github.com/golang/go/issues/4373, this error string should not
 	// change. This is not ideal, but since the worst that could happen here is
 	// some superfluous logging, it is acceptable.
 	if err.Error() == "use of closed network connection" {
 		return true
 	}
+
 	return false
 }