txn: check TxnError in response (#4664)

The response TxnMeta needs to be checked only if TxnError is not empty, otherwise the error message returned will be incorrect

Approved by: @reusee, @lni

pkg/txn/client/operator.go

@@ -479,22 +479,22 @@ func (tc *txnOperator) handleError(result *rpc.SendResult, err error) (*rpc.Send
 func (tc *txnOperator) handleErrorResponse(resp txn.TxnResponse) error {
 	switch resp.Method {
 	case txn.TxnMethod_Read:
-		if err := tc.checkResponseTxnStatusForReadWrite(resp.Txn); err != nil {
+		if err := tc.checkResponseTxnStatusForReadWrite(resp); err != nil {
 			return err
 		}
 		return tc.checkTxnError(resp.TxnError, readTxnErrors)
 	case txn.TxnMethod_Write:
-		if err := tc.checkResponseTxnStatusForReadWrite(resp.Txn); err != nil {
+		if err := tc.checkResponseTxnStatusForReadWrite(resp); err != nil {
 			return err
 		}
 		return tc.checkTxnError(resp.TxnError, writeTxnErrors)
 	case txn.TxnMethod_Commit:
-		if err := tc.checkResponseTxnStatusForCommit(resp.Txn); err != nil {
+		if err := tc.checkResponseTxnStatusForCommit(resp); err != nil {
 			return err
 		}
 		return tc.checkTxnError(resp.TxnError, commitTxnErrors)
 	case txn.TxnMethod_Rollback:
-		if err := tc.checkResponseTxnStatusForRollback(resp.Txn); err != nil {
+		if err := tc.checkResponseTxnStatusForRollback(resp); err != nil {
 			return err
 		}
 		return tc.checkTxnError(resp.TxnError, rollbackTxnErrors)
@@ -505,7 +505,12 @@ func (tc *txnOperator) handleErrorResponse(resp txn.TxnResponse) error {
 	return nil
 }
 
-func (tc *txnOperator) checkResponseTxnStatusForReadWrite(txnMeta *txn.TxnMeta) error {
+func (tc *txnOperator) checkResponseTxnStatusForReadWrite(resp txn.TxnResponse) error {
+	if resp.TxnError != nil {
+		return nil
+	}
+
+	txnMeta := resp.Txn
 	if txnMeta == nil {
 		return moerr.New(moerr.ErrTxnClosed)
 	}
@@ -541,7 +546,12 @@ func (tc *txnOperator) checkTxnError(txnError *txn.TxnError, possibleErrorMap ma
 	return nil
 }
 
-func (tc *txnOperator) checkResponseTxnStatusForCommit(txnMeta *txn.TxnMeta) error {
+func (tc *txnOperator) checkResponseTxnStatusForCommit(resp txn.TxnResponse) error {
+	if resp.TxnError != nil {
+		return nil
+	}
+
+	txnMeta := resp.Txn
 	if txnMeta == nil {
 		return moerr.New(moerr.ErrTxnClosed)
 	}
@@ -556,7 +566,12 @@ func (tc *txnOperator) checkResponseTxnStatusForCommit(txnMeta *txn.TxnMeta) err
 	return nil
 }
 
-func (tc *txnOperator) checkResponseTxnStatusForRollback(txnMeta *txn.TxnMeta) error {
+func (tc *txnOperator) checkResponseTxnStatusForRollback(resp txn.TxnResponse) error {
+	if resp.TxnError != nil {
+		return nil
+	}
+
+	txnMeta := resp.Txn
 	if txnMeta == nil {
 		return moerr.New(moerr.ErrTxnClosed)
 	}