feat(unierr): allow nil errors (close #125)

unierr/error.go

@@ -44,6 +44,12 @@ func Newf(code codes.Code, format string, args ...interface{}) *Error {
 
 // Wrap annotates an error with a codes.Code
 func Wrap(err error, code codes.Code) *Error {
+	if err == nil {
+		return &Error{
+			msg:  code.String(),
+			code: code,
+		}
+	}
 	err = errors.WithStack(err)
 	return &Error{
 		err:  err,
@@ -181,6 +187,9 @@ type stackTracer interface {
 
 // StackTrace implements the interface of errors.Wrap()
 func (e *Error) StackTrace() errors.StackTrace {
+	if e.err == nil {
+		return nil
+	}
 	if err, ok := e.err.(stackTracer); ok {
 		return err.StackTrace()
 	}

unierr/error_test.go

@@ -2,11 +2,12 @@ package unierr
 
 import (
 	"encoding/json"
-	"errors"
-	"github.com/stretchr/testify/assert"
-	"google.golang.org/grpc/codes"
 	"strings"
 	"testing"
+
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/assert"
+	"google.golang.org/grpc/codes"
 )
 
 func TestServerError_UnmarshalJSON(t *testing.T) {
@@ -61,3 +62,62 @@ func TestServerError_CustomPrinter(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, []byte(`{"code":10,"message":"FOO"}`), bytes)
 }
+
+func TestWrap(t *testing.T) {
+	type args struct {
+		err  error
+		code codes.Code
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{"err_nil", args{nil, codes.Aborted}, codes.Aborted.String()},
+		{"err_foo", args{errors.New("foo"), codes.Aborted}, "foo"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			testError := Wrap(tt.args.err, tt.args.code)
+			assert.Equal(t, tt.want, testError.Error())
+			byts, err := json.Marshal(testError)
+			assert.NoError(t, err)
+			var result *Error
+			err = json.Unmarshal(byts, &result)
+			assert.NoError(t, err)
+			assert.Equal(t, testError.code, result.code)
+			assert.Equal(t, testError.msg, result.msg)
+			assert.True(t, IsAbortedErr(result))
+
+			status := testError.GRPCStatus()
+			assert.Equal(t, codes.Aborted, status.Code())
+			assert.Equal(t, testError.Error(), status.Message())
+
+		})
+	}
+}
+
+func TestError_StackTrace(t *testing.T) {
+	type args struct {
+		err  error
+		code codes.Code
+	}
+	tests := []struct {
+		name string
+		args args
+		want int
+	}{
+		{"err_nil", args{nil, codes.Aborted}, 0},
+		{"err_foo", args{errors.New("foo"), codes.Aborted}, 3},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			e := &Error{
+				err:  tt.args.err,
+				code: tt.args.code,
+			}
+			s := e.StackTrace()
+			assert.Equal(t, tt.want, len(s))
+		})
+	}
+}