add err message for dumpling

v4/export/dump.go

@@ -71,7 +71,7 @@ func NewDumper(ctx context.Context, conf *Config) (*Dumper, error) {
 		openSQLDB,
 		detectServerInfo,
 		resolveAutoConsistency,
-
+		validateResolveAutoConsistency,
 		tidbSetPDClientForGC,
 		tidbGetSnapshot,
 		tidbStartGCSavepointUpdateService,
@@ -1074,6 +1074,14 @@ func resolveAutoConsistency(d *Dumper) error {
 	return nil
 }
 
+func validateResolveAutoConsistency(d *Dumper) error {
+	conf := d.conf
+	if conf.Consistency != consistencyTypeSnapshot && conf.Snapshot != "" {
+		return errors.Errorf("can't specify --snapshot when --consistency isn't snapshot, resolved consistency: %s", conf.Consistency)
+	}
+	return nil
+}
+
 // tidbSetPDClientForGC is an initialization step of Dumper.
 func tidbSetPDClientForGC(d *Dumper) error {
 	tctx, si, pool := d.tctx, d.conf.ServerInfo, d.dbHandle

v4/export/prepare_test.go

@@ -9,6 +9,7 @@ import (
 	"testing"
 
 	tcontext "github.com/pingcap/dumpling/v4/context"
+	"github.com/pingcap/errors"
 	"github.com/stretchr/testify/require"
 
 	"github.com/DATA-DOG/go-sqlmock"
@@ -307,3 +308,37 @@ func TestConfigValidation(t *testing.T) {
 	conf.FileType = "rand_str"
 	require.EqualError(t, adjustFileFormat(conf), "unknown config.FileType 'rand_str'")
 }
+
+func TestValidateResolveAutoConsistency(t *testing.T) {
+	t.Parallel()
+
+	conf1 := defaultConfigForTest(t)
+	d := &Dumper{conf: conf1}
+	conf := d.conf
+
+	testCases := []struct {
+		confConsistency string
+		confSnapshot    string
+		err             error
+	}{
+		{consistencyTypeAuto, "", nil},
+		{consistencyTypeAuto, "123", errors.New("can't specify --snapshot when --consistency isn't snapshot, resolved consistency: auto")},
+		{consistencyTypeFlush, "", nil},
+		{consistencyTypeFlush, "456", errors.New("can't specify --snapshot when --consistency isn't snapshot, resolved consistency: flush")},
+		{consistencyTypeLock, "", nil},
+		{consistencyTypeLock, "789", errors.New("can't specify --snapshot when --consistency isn't snapshot, resolved consistency: lock")},
+		{consistencyTypeSnapshot, "", nil},
+		{consistencyTypeSnapshot, "456", nil},
+		{consistencyTypeNone, "", nil},
+		{consistencyTypeNone, "123", errors.New("can't specify --snapshot when --consistency isn't snapshot, resolved consistency: none")},
+	}
+	for _, testCase := range testCases {
+		conf.Consistency = testCase.confConsistency
+		conf.Snapshot = testCase.confSnapshot
+		if testCase.err == nil {
+			require.NoError(t, validateResolveAutoConsistency(d))
+		} else {
+			require.EqualError(t, validateResolveAutoConsistency(d), testCase.err.Error())
+		}
+	}
+}