time column type string formatting and test coverage (#891)

* time format test coverage and formatting

* remove whitespace

* drop comments, use require.NoError

mysql/util.go

@@ -324,35 +324,40 @@ func FormatBinaryDateTime(n int, data []byte) ([]byte, error) {
 
 func FormatBinaryTime(n int, data []byte) ([]byte, error) {
 	if n == 0 {
-		return []byte("0000-00-00"), nil
+		return []byte("00:00:00"), nil
 	}
 
 	var sign byte
 	if data[0] == 1 {
 		sign = byte('-')
 	}
 
+	var bytes []byte
 	switch n {
 	case 8:
-		return []byte(fmt.Sprintf(
+		bytes = []byte(fmt.Sprintf(
 			"%c%02d:%02d:%02d",
 			sign,
 			uint16(data[1])*24+uint16(data[5]),
 			data[6],
 			data[7],
-		)), nil
+		))
 	case 12:
-		return []byte(fmt.Sprintf(
+		bytes = []byte(fmt.Sprintf(
 			"%c%02d:%02d:%02d.%06d",
 			sign,
 			uint16(data[1])*24+uint16(data[5]),
 			data[6],
 			data[7],
 			binary.LittleEndian.Uint32(data[8:12]),
-		)), nil
+		))
 	default:
 		return nil, errors.Errorf("invalid time packet length %d", n)
 	}
+	if bytes[0] == 0 {
+		return bytes[1:], nil
+	}
+	return bytes, nil
 }
 
 var (

mysql/util_test.go

@@ -23,3 +23,31 @@ func TestCompareServerVersions(t *testing.T) {
 		require.Equal(t, test.Expect, got)
 	}
 }
+
+func TestFormatBinaryTime(t *testing.T) {
+	tests := []struct {
+		Data   []byte
+		Expect string
+		Error  bool
+	}{
+		{Data: []byte{}, Expect: "00:00:00"},
+		{Data: []byte{0, 0, 0, 0, 0, 0, 0, 10}, Expect: "00:00:10"},
+		{Data: []byte{0, 0, 0, 0, 0, 0, 1, 40}, Expect: "00:01:40"},
+		{Data: []byte{1, 0, 0, 0, 0, 0, 1, 40}, Expect: "-00:01:40"},
+		{Data: []byte{1, 1, 0, 0, 0, 1, 1, 40}, Expect: "-25:01:40"},
+		{Data: []byte{1, 1, 0, 0, 0, 1, 1, 40, 1, 2, 3, 0}, Expect: "-25:01:40.197121"},
+		{Data: []byte{0}, Error: true},
+	}
+
+	for _, test := range tests {
+		n := len(test.Data)
+
+		got, err := FormatBinaryTime(n, test.Data)
+		if test.Error {
+			require.Error(t, err)
+		} else {
+			require.NoError(t, err)
+		}
+		require.Equal(t, test.Expect, string(got), "test case %v", test.Data)
+	}
+}