Handle null inputs in get_range

jsonpath.go

@@ -23,7 +23,6 @@ import (
 var ErrGetFromNullObj = errors.New("get attribute from null object")
 var ErrKeyError = errKind.NewKind("key error: %s not found in object")
 
-
 func JsonPathLookup(obj interface{}, jpath string) (interface{}, error) {
 	c, err := Compile(jpath)
 	if err != nil {
@@ -264,7 +263,7 @@ func tokenize(query string) ([]string, error) {
 }
 
 /*
- op: "root", "key", "idx", "range", "filter", "scan"
+op: "root", "key", "idx", "range", "filter", "scan"
 */
 func parse_token(token string) (op string, key string, args interface{}, err error) {
 	if token == "$" {
@@ -441,7 +440,11 @@ func get_idx(obj interface{}, idx int) (interface{}, error) {
 }
 
 func get_range(obj, frm, to interface{}) (interface{}, error) {
-	switch reflect.TypeOf(obj).Kind() {
+	typeOfObj := reflect.TypeOf(obj)
+	if typeOfObj == nil {
+		return nil, ErrGetFromNullObj
+	}
+	switch typeOfObj.Kind() {
 	case reflect.Slice:
 		length := reflect.ValueOf(obj).Len()
 		_frm := 0

jsonpath_test.go

@@ -116,7 +116,7 @@ func Test_jsonpath_JsonPathLookup_1(t *testing.T) {
 	if res_v, ok := res.([]interface{}); ok != true || res_v[0].(float64) != 8.95 || res_v[1].(float64) != 12.99 || res_v[2].(float64) != 8.99 || res_v[3].(float64) != 22.99 {
 		t.Errorf("exp: [8.95, 12.99, 8.99, 22.99], got: %v", res)
 	}
-	
+
 	// range
 	res, err = JsonPathLookup(json_data, "$.store.book[0:1].price")
 	t.Log(err, res)
@@ -132,6 +132,25 @@ func Test_jsonpath_JsonPathLookup_1(t *testing.T) {
 			t.Errorf("title are wrong: %v", res)
 		}
 	}
+
+	// null input
+	res, err = JsonPathLookup(nil, "$.store")
+	if err == nil {
+		t.Errorf("expected error from nil json data")
+	}
+
+	res, err = JsonPathLookup(nil, "$[*]")
+	if err == nil {
+		t.Errorf("expected error from nil json data")
+	}
+
+	res, err = JsonPathLookup(nil, "$")
+	if err != nil {
+		t.Errorf("unexpected error for JsonPathLookup(nil, \"$\"): %s", err.Error())
+	}
+	if res != nil {
+		t.Errorf("exp: nil, got: %v", res)
+	}
 }
 
 func Test_jsonpath_JsonPathLookup_filter(t *testing.T) {
@@ -588,15 +607,15 @@ func Test_jsonpath_get_scan(t *testing.T) {
 	}
 
 	obj4 := map[string]interface{}{
-		"key1" : "abc",
-		"key2" : 123,
-		"key3" : map[string]interface{}{
+		"key1": "abc",
+		"key2": 123,
+		"key3": map[string]interface{}{
 			"a": 1,
 			"b": 2,
 			"c": 3,
 		},
-		"key4" : []interface{}{1,2,3},
-		"key5" : nil,
+		"key4": []interface{}{1, 2, 3},
+		"key5": nil,
 	}
 	res, err = get_scan(obj4)
 	res_v, ok = res.([]interface{})