From 6f31b3ae404a7cd47885af0a1cc77fa7ae34e4c0 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Wed, 17 Apr 2024 12:54:49 +0200
Subject: [PATCH] server: fix failingListener data race in tests

    WARNING: DATA RACE
    Read at 0x00c00002b788 by goroutine 44:
      github.com/emersion/go-smtp_test.(*failingListener).Close()
          /home/simon/src/go-smtp/server_test.go:193 +0x34
      github.com/emersion/go-smtp.(*Server).Close()
          /home/simon/src/go-smtp/server.go:251 +0x181
      github.com/emersion/go-smtp_test.TestServerAcceptErrorHandling()
          /home/simon/src/go-smtp/server_test.go:323 +0x771
      testing.tRunner()
          /usr/lib/go/src/testing/testing.go:1689 +0x21e
      testing.(*T).Run.gowrap1()
          /usr/lib/go/src/testing/testing.go:1742 +0x44

    Previous write at 0x00c00002b788 by goroutine 45:
      github.com/emersion/go-smtp_test.(*failingListener).Close()
          /home/simon/src/go-smtp/server_test.go:195 +0xdb
      github.com/emersion/go-smtp_test.TestServerAcceptErrorHandling.func1()
          /home/simon/src/go-smtp/server_test.go:316 +0xab

    Goroutine 44 (running) created at:
      testing.(*T).Run()
          /usr/lib/go/src/testing/testing.go:1742 +0x825
      testing.runTests.func1()
          /usr/lib/go/src/testing/testing.go:2161 +0x85
      testing.tRunner()
          /usr/lib/go/src/testing/testing.go:1689 +0x21e
      testing.runTests()
          /usr/lib/go/src/testing/testing.go:2159 +0x8be
      testing.(*M).Run()
          /usr/lib/go/src/testing/testing.go:2027 +0xf17
      main.main()
          _testmain.go:163 +0x2bd

    Goroutine 45 (finished) created at:
      github.com/emersion/go-smtp_test.TestServerAcceptErrorHandling()
          /home/simon/src/go-smtp/server_test.go:314 +0x5d5
      testing.tRunner()
          /usr/lib/go/src/testing/testing.go:1689 +0x21e
      testing.(*T).Run.gowrap1()
          /usr/lib/go/src/testing/testing.go:1742 +0x44
---
 server_test.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/server_test.go b/server_test.go
index b0bf4c0..add9390 100644
--- a/server_test.go
+++ b/server_test.go
@@ -10,6 +10,7 @@ import (
 	"log"
 	"net"
 	"strings"
+	"sync"
 	"testing"
 
 	"github.com/emersion/go-sasl"
@@ -173,6 +174,7 @@ func (s *session) LMTPData(r io.Reader, collector smtp.StatusCollector) error {
 type failingListener struct {
 	c      chan error
 	closed bool
+	mu     sync.Mutex
 }
 
 func newFailingListener() *failingListener {
@@ -180,6 +182,9 @@ func newFailingListener() *failingListener {
 }
 
 func (l *failingListener) Send(err error) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
 	if !l.closed {
 		l.c <- err
 	}
@@ -190,6 +195,9 @@ func (l *failingListener) Accept() (net.Conn, error) {
 }
 
 func (l *failingListener) Close() error {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
 	if !l.closed {
 		close(l.c)
 		l.closed = true