Follow upstream for HELO during Quit bug

I reported the bug I fixed in 74fa3f6f62 to Go upstream. They fixed simpler by just ignoring the error (See: https://go.dev/cl/622476). We follow this patch accordingly. The upstream test has been adopted as well.

smtp/smtp.go

@@ -554,20 +554,9 @@ func (c *Client) Noop() error {
 
 // Quit sends the QUIT command and closes the connection to the server.
 func (c *Client) Quit() error {
-	// If we already tried to send a EHLO/HELO but it failed, we still need to be able to send
+	// See https://github.com/golang/go/issues/70011
-	// a QUIT to close the connection.
+	_ = c.hello() // ignore error; we're quitting anyhow
-	// c.hello() will return the global helloErr of the Client, which will always be set if the HELO
+
-	// failed before. Therefore if we already sent a HELO and the error is not nil, we skip another
-	// EHLO/HELO try
-	c.mutex.RLock()
-	didHello := c.didHello
-	helloErr := c.helloError
-	c.mutex.RUnlock()
-	if !didHello || helloErr == nil {
-		if err := c.hello(); err != nil {
-			return err
-		}
-	}
 	_, _, err := c.cmd(221, "QUIT")
 	if err != nil {
 		return err

smtp/smtp_test.go

@@ -900,6 +900,35 @@ Goodbye.
 QUIT
 `
 
+func TestHELOFailed(t *testing.T) {
+	serverLines := `502 EH?
+502 EH?
+221 OK
+`
+	clientLines := `EHLO localhost
+HELO localhost
+QUIT
+`
+	server := strings.Join(strings.Split(serverLines, "\n"), "\r\n")
+	client := strings.Join(strings.Split(clientLines, "\n"), "\r\n")
+	var cmdbuf strings.Builder
+	bcmdbuf := bufio.NewWriter(&cmdbuf)
+	var fake faker
+	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
+	c := &Client{Text: textproto.NewConn(fake), localName: "localhost"}
+	if err := c.Hello("localhost"); err == nil {
+		t.Fatal("expected EHLO to fail")
+	}
+	if err := c.Quit(); err != nil {
+		t.Errorf("QUIT failed: %s", err)
+	}
+	_ = bcmdbuf.Flush()
+	actual := cmdbuf.String()
+	if client != actual {
+		t.Errorf("Got:\n%s\nWant:\n%s", actual, client)
+	}
+}
+
 func TestExtensions(t *testing.T) {
 	fake := func(server string) (c *Client, bcmdbuf *bufio.Writer, cmdbuf *strings.Builder) {
 		server = strings.Join(strings.Split(server, "\n"), "\r\n")