better catch multilevel errors

Author: im-kulikov

helium.go

@@ -128,22 +128,25 @@ func CatchTrace(err error) {
 	// digging into the root of the problem
 	for {
 		var (
+			ok bool
 			v  = reflect.ValueOf(err)
 			fn reflect.Value
 		)
 
 		if v.Type().Kind() != reflect.Struct {
 			break
-		}
-
-		if !v.FieldByName("Reason").IsValid() || !v.FieldByName("Func").IsValid() {
+		} else if !v.FieldByName("Reason").IsValid() {
 			break
+		} else if v.FieldByName("Func").IsValid() {
+			fn = v.FieldByName("Func")
 		}
 
-		fn = v.FieldByName("Func")
-		err = v.FieldByName("Reason").Interface().(error)
-
 		fmt.Printf("Place: %#v\nReason: %s\n\n", fn, err)
+
+		if err, ok = v.FieldByName("Reason").Interface().(error); !ok {
+			err = v.Interface().(error)
+			break
+		}
 	}
 
 	panic(err)

helium_test.go

@@ -8,6 +8,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"strconv"
 	"testing"
 
 	"bou.ke/monkey"
@@ -25,6 +26,12 @@ type (
 	heliumErrApp struct{}
 
 	Error string
+
+	TestError struct {
+		Index  int
+		Func   interface{}
+		Reason error
+	}
 )
 
 const ErrTest = Error("test")
@@ -33,6 +40,10 @@ func (e Error) Error() string {
 	return string(e)
 }
 
+func (e TestError) Error() string {
+	return "error level: " + strconv.Itoa(e.Index)
+}
+
 func (h heliumApp) Run(ctx context.Context) error    { return nil }
 func (h heliumErrApp) Run(ctx context.Context) error { return ErrTest }
 
@@ -253,5 +264,26 @@ func TestHelium(t *testing.T) {
 
 			require.Empty(t, exitCode)
 		})
+
+		t.Run("should catch multi level errors", func(t *testing.T) {
+			var exitCode int
+
+			monkey.Patch(os.Exit, func(code int) { exitCode = code; panic(code) })
+			monkey.Patch(log.Fatal, func(...interface{}) { exitCode = 2; panic(exitCode) })
+
+			require.Panics(t, func() {
+				CatchTrace(TestError{
+					Index: 1,
+					Reason: TestError{
+						Index: 2,
+						Reason: TestError{
+							Index: 3,
+						},
+					},
+				})
+			})
+
+			require.Empty(t, exitCode)
+		})
 	})
 }