more specific submission errors

Author: pascaldekloe

client.go

@@ -168,8 +168,8 @@ func (c *Config) valid() error {
 	return nil
 }
 
-// NewCONNREQ returns a new packet.
-func (c *Config) newCONNREQ(clientID []byte) []byte {
+// NewConnectReq returns a new CONNECT packet conform the configuration.
+func (c *Config) newConnectReq(clientID []byte) []byte {
 	size := 12 + len(clientID)
 	var flags uint
 
@@ -1044,9 +1044,9 @@ func (c *Client) resend(conn net.Conn, seqNoOffset uint, seq *seq, space uint) e
 
 func (c *Client) handshake(conn net.Conn, config *Config, clientID []byte) (*bufio.Reader, error) {
 	// send request
-	err := writeTo(conn, config.newCONNREQ(clientID), c.PauseTimeout)
+	err := writeTo(conn, config.newConnectReq(clientID), c.PauseTimeout)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("mqtt: connection fatal during CONNECT submission; %w", err)
 	}
 
 	r := bufio.NewReaderSize(conn, readBufSize)

mqtt_test.go

@@ -55,7 +55,7 @@ func TestErrorClasses(t *testing.T) {
 	}
 }
 
-func TestNewCONNREQ(t *testing.T) {
+func TestNewConnectReq(t *testing.T) {
 	c := &Config{
 		Dialer: func(context.Context) (net.Conn, error) {
 			return nil, errors.New("dialer call not allowed for test")
@@ -71,7 +71,7 @@ func TestNewCONNREQ(t *testing.T) {
 	c.Will.AtLeastOnce = true
 	c.Will.ExactlyOnce = true
 
-	got := c.newCONNREQ([]byte("#🤖"))
+	got := c.newConnectReq([]byte("#🤖"))
 	want := []byte{0x10, 37, 0, 4, 'M', 'Q', 'T', 'T', 4, 0b1111_0110, 0x0e, 0x10,
 		0, 5, '#', 0xF0, 0x9F, 0xA4, 0x96,
 		0, 6, 0xe2, 0x98, 0xaf, 0xef, 0xb8, 0x8f,

request.go

@@ -28,12 +28,12 @@ var ErrAbandoned = errors.New("mqtt: request abandoned after submission")
 // status of the execution remains unknown, because there is no telling how much
 // of the payload actually reached the broker. Connection loss after submision
 // causes ErrBreak instead.
-var ErrSubmit = errors.New("mqtt: connection lost during submission")
+var ErrSubmit = errors.New("mqtt: connection fatal during submission")
 
 // ErrBreak signals that the connection was lost after a request was send, and
 // before a response was received. The status of the execution remains unknown,
 // similar to ErrSubmit.
-var ErrBreak = errors.New("mqtt: connection lost while awaiting response")
+var ErrBreak = errors.New("mqtt: connection fatal while awaiting response")
 
 // BufSize should fit topic names with a bit of overhead.
 const bufSize = 128