lua: json: add optional argument in the json parse() method to limit the number of recursions

This allows partially parsing a json object, allowing some parts to be
passed on as strings to another component that does its own parsing
(ex. a pipewire module)

modules/module-lua-scripting/api/json.c

@@ -95,7 +95,7 @@ spa_json_is_object (lua_State *L)
 }
 
 static void
-push_luajson (lua_State *L, WpSpaJson *json)
+push_luajson (lua_State *L, WpSpaJson *json, gint n_recursions)
 {
   /* Null */
   if (wp_spa_json_is_null (json)) {
@@ -124,20 +124,20 @@ push_luajson (lua_State *L, WpSpaJson *json)
   }
 
   /* Array */
-  else if (wp_spa_json_is_array (json)) {
+  else if (wp_spa_json_is_array (json) && n_recursions > 0) {
     g_auto (GValue) item = G_VALUE_INIT;
     g_autoptr (WpIterator) it = wp_spa_json_new_iterator (json);
     guint i = 1;
     lua_newtable (L);
     for (; wp_iterator_next (it, &item); g_value_unset (&item)) {
       WpSpaJson *j = g_value_get_boxed (&item);
-      push_luajson (L, j);
+      push_luajson (L, j, n_recursions - 1);
       lua_rawseti (L, -2, i++);
     }
   }
 
   /* Object */
-  else if (wp_spa_json_is_object (json)) {
+  else if (wp_spa_json_is_object (json) && n_recursions > 0) {
     g_auto (GValue) item = G_VALUE_INIT;
     g_autoptr (WpIterator) it = wp_spa_json_new_iterator (json);
     lua_newtable (L);
@@ -151,7 +151,7 @@ push_luajson (lua_State *L, WpSpaJson *json)
       if (!wp_iterator_next (it, &item))
         break;
       value = g_value_get_boxed (&item);
-      push_luajson (L, value);
+      push_luajson (L, value, n_recursions - 1);
       lua_setfield (L, -2, key_str);
     }
   }
@@ -168,7 +168,8 @@ static int
 spa_json_parse (lua_State *L)
 {
   WpSpaJson *json = wplua_checkboxed (L, 1, WP_TYPE_SPA_JSON);
-  push_luajson (L, json);
+  gint n_recursions = luaL_opt (L, luaL_checkinteger, 2, INT_MAX);
+  push_luajson (L, json, n_recursions);
   return 1;
 }
 

tests/wplua/scripts/json.lua

@@ -186,3 +186,40 @@ assert (val.name == "wireplumber")
 assert (val.version[1] == 0)
 assert (val.version[2] == 4)
 assert (val.version[3] == 7)
+
+-- recursion limit
+json = Json.Raw ("{ name = wireplumber, version = [0, 4, 15], args = { test = [0, 1] } }")
+
+val = json:parse (0)
+assert (type (val) == "string")
+assert (val == "{ name = wireplumber, version = [0, 4, 15], args = { test = [0, 1] } }")
+
+val = json:parse (1)
+assert (type (val) == "table")
+assert (val.name == "wireplumber")
+assert (type (val.version) == "string")
+assert (val.version == "[0, 4, 15]")
+assert (type (val.args) == "string")
+assert (val.args == "{ test = [0, 1] }")
+
+val = json:parse(2)
+assert (type (val) == "table")
+assert (val.name == "wireplumber")
+assert (type (val.version) == "table")
+assert (val.version[1] == 0)
+assert (val.version[2] == 4)
+assert (val.version[3] == 15)
+assert (type (val.args) == "table")
+assert (val.args.test == "[0, 1]")
+
+val = json:parse(3)
+assert (type (val) == "table")
+assert (val.name == "wireplumber")
+assert (type (val.version) == "table")
+assert (val.version[1] == 0)
+assert (val.version[2] == 4)
+assert (val.version[3] == 15)
+assert (type (val.args) == "table")
+assert (type (val.args.test) == "table")
+assert (val.args.test[1] == 0)
+assert (val.args.test[2] == 1)