Add Errors.Unwrap method (#24)

* Add Errors.Unwrap method

This allows us to use errors.Is with errors returned from a failed validation.

* Remove errors.Is test

This only works from go1.20 onwards. And this project targets 1.13

Author: goodevilgenius

error.go

@@ -141,6 +141,17 @@ func (es Errors) Error() string {
 	return s.String()
 }
 
+// Unwrap returns a slice of the non-nil errors in the Errors.
+func (es Errors) Unwrap() []error {
+	errs := make([]error, 0, len(es))
+	for _, err := range es {
+		if err != nil {
+			errs = append(errs, err)
+		}
+	}
+	return errs
+}
+
 // MarshalJSON converts the Errors into a valid JSON.
 func (es Errors) MarshalJSON() ([]byte, error) {
 	errs := map[string]interface{}{}

error_test.go

@@ -70,6 +70,19 @@ func TestErrors_Filter(t *testing.T) {
 	assert.Nil(t, errs.Filter())
 }
 
+func TestErrors_Unwrap(t *testing.T) {
+	errs := Errors{
+		"B": errors.New("B1"),
+		"C": nil,
+		"A": errors.New("A1"),
+	}
+
+	unwrapped := errs.Unwrap()
+	assert.Contains(t, unwrapped, errs["B"])
+	assert.Contains(t, unwrapped, errs["A"])
+	assert.Len(t, unwrapped, 2)
+}
+
 func TestErrorObject_SetCode(t *testing.T) {
 	err := NewError("A", "msg").(ErrorObject)