eth/tracers/native: fix flatCallTracer Stop() bug

eth/tracers/native/call_flat.go

@@ -224,6 +224,7 @@ func (t *flatCallTracer) GetResult() (json.RawMessage, error) {
 
 // Stop terminates execution of the tracer at the first opportune moment.
 func (t *flatCallTracer) Stop(err error) {
+	t.reason = err
 	t.tracer.Stop(err)
 }
 

eth/tracers/native/call_flat_test.go

@@ -0,0 +1,45 @@
+package native_test
+
+import (
+	"encoding/json"
+	"errors"
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/tracing"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/eth/tracers"
+	"github.com/ethereum/go-ethereum/params"
+	"github.com/stretchr/testify/require"
+)
+
+func TestCallFlatStop(t *testing.T) {
+
+	ctx := &tracers.Context{}
+
+	tracer, err := tracers.DefaultDirectory.New("flatCallTracer", ctx, json.RawMessage(`{}`))
+	require.NoError(t, err)
+
+	// this error should be returned by GetResult
+	stopError := errors.New("stop error")
+
+	// simulate a transaction
+	tx := types.NewTransaction(0, common.Address{}, big.NewInt(0), 0, big.NewInt(0), nil)
+
+	tracer.OnTxStart(&tracing.VMContext{
+		ChainConfig: params.MainnetChainConfig,
+	}, tx, common.Address{})
+
+	tracer.OnEnter(0, byte(vm.CALL), common.Address{}, common.Address{}, nil, 0, big.NewInt(0))
+
+	// stop before the transaction is finished
+	tracer.Stop(stopError)
+
+	tracer.OnTxEnd(&types.Receipt{GasUsed: 0}, nil)
+
+	// check that the error is returned by GetResult
+	_, tracerError := tracer.GetResult()
+	require.Equal(t, stopError, tracerError)
+}