Merge pull request #10 from upfluence/am/multi-wrap

multi: Improve multi error recursive wrapping

multi/multi_error.go

@@ -9,9 +9,8 @@ import (
 
 type multiError []error
 
-func (errs multiError) Errors() []error {
-	return errs
-}
+func (errs multiError) Unwrap() []error { return errs }
+func (errs multiError) Errors() []error { return errs }
 
 func (errs multiError) Error() string {
 	var b strings.Builder
@@ -66,11 +65,7 @@ func Wrap(errs []error) error {
 			continue
 		}
 
-		if e, ok := err.(MultiError); ok {
-			merrs = append(merrs, e.Errors()...)
-		} else {
-			merrs = append(merrs, err)
-		}
+		merrs = append(merrs, ExtractErrors(err)...)
 	}
 
 	switch len(merrs) {
@@ -106,5 +101,11 @@ func ExtractErrors(err error) []error {
 		return []error{err}
 	}
 
-	return ExtractErrors(nerr)
+	errs := ExtractErrors(nerr)
+
+	if len(errs) == 1 && errs[0] == nerr {
+		return []error{err}
+	}
+
+	return errs
 }

multi/multi_error_test.go

@@ -6,6 +6,7 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	"github.com/upfluence/errors"
+	"github.com/upfluence/errors/multi"
 	"github.com/upfluence/errors/tags"
 )
 
@@ -27,6 +28,12 @@ func TestCombining(t *testing.T) {
 		{errs: []error{}},
 		{errs: []error{nil, nil, errors.Combine(nil, foo)}, want: foo},
 		{errs: []error{foo}, want: foo},
+		{
+			errs: []error{
+				foo, errors.Combine(foo, foo),
+			},
+			want: multi.Combine(foo, foo, foo),
+		},
 	} {
 		assert.Equal(t, tt.want, errors.Cause(errors.WrapErrors(tt.errs)))
 	}