Allow ConfigParseError to unwrap (#1433)

* Allow ConfigParseError to unwrap

* wip

* Avoid pointer type

util.go

@@ -31,6 +31,11 @@ func (pe ConfigParseError) Error() string {
 	return fmt.Sprintf("While parsing config: %s", pe.err.Error())
 }
 
+// Unwrap returns the wrapped error.
+func (pe ConfigParseError) Unwrap() error {
+	return pe.err
+}
+
 // toCaseInsensitiveValue checks if the value is a  map;
 // if so, create a copy and lower-case the keys recursively.
 func toCaseInsensitiveValue(value interface{}) interface{} {

viper_test.go

@@ -8,6 +8,7 @@ package viper
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"io"
 	"io/ioutil"
 	"os"
@@ -1573,6 +1574,18 @@ func TestWrongDirsSearchNotFoundForMerge(t *testing.T) {
 	assert.Equal(t, `default`, v.GetString(`key`))
 }
 
+var yamlInvalid = []byte(`hash: map
+- foo
+- bar
+`)
+
+func TestUnwrapParseErrors(t *testing.T) {
+	SetConfigType("yaml")
+	if !errors.As(ReadConfig(bytes.NewBuffer(yamlInvalid)), &ConfigParseError{}) {
+		t.Fatalf("not a ConfigParseError")
+	}
+}
+
 func TestSub(t *testing.T) {
 	v := New()
 	v.SetConfigType("yaml")