Handle parsing errors for mv.Exists argument

exists.go

@@ -1,7 +1,9 @@
 package mxj
 
-// Checks whether the path exists
-func (mv Map) Exists(path string, subkeys ...string) bool {
+// Checks whether the path exists. If err != nil then 'false' is returned
+// along with the error encountered parsing either the "path" or "subkeys"
+// argument.
+func (mv Map) Exists(path string, subkeys ...string) (bool, error) {
 	v, err := mv.ValuesForPath(path, subkeys...)
-	return err == nil && len(v) > 0
+	return (err == nil && len(v) > 0), err
 }

exists_test.go

@@ -14,11 +14,11 @@ func TestExists(t *testing.T) {
 	}
 	mv := Map(m)
 
-	if !mv.Exists("Div.Colour") {
+	if v, _ := mv.Exists("Div.Colour"); !v {
 		t.Fatal("Haven't found an existing element")
 	}
 
-	if mv.Exists("Div.Color") {
+	if v, _ := mv.Exists("Div.Color"); v {
 		t.Fatal("Have found a non existing element")
 	}
 }

remove_test.go

@@ -15,7 +15,7 @@ func TestRemove(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if mv.Exists("Div.Colour") {
+	if v, _ := mv.Exists("Div.Colour"); v {
 		t.Fatal("removed key still remain")
 	}
 }

rename.go

@@ -6,13 +6,20 @@ import (
 )
 
 // RenameKey renames a key in a Map.
-// It works only for nested maps. It doesn't work for cases when it buried in a list.
+// It works only for nested maps. 
+// It doesn't work for cases when the key is in a list.
 func (mv Map) RenameKey(path string, newName string) error {
-	if !mv.Exists(path) {
+	var v bool
+	var err error
+	if v, err = mv.Exists(path); err == nil && !v {
 		return errors.New("RenameKey: path not found: " + path)
+	} else if err != nil {
+		return err
 	}
-	if mv.Exists(parentPath(path) + "." + newName) {
+	if v, err = mv.Exists(parentPath(path) + "." + newName); err == nil && v {
 		return errors.New("RenameKey: key already exists: " + newName)
+	} else if err != nil {
+		return err
 	}
 
 	m := map[string]interface{}(mv)

rename_test.go

@@ -1,10 +1,12 @@
 package mxj
 
 import (
+	"fmt"
 	"testing"
 )
 
 func TestRenameKey(t *testing.T) {
+	fmt.Println("------------ rename_test.go")
 	m := map[string]interface{}{
 		"Div": map[string]interface{}{
 			"Colour": "blue",