degesch: Lua: allow arbitrary userdata properties

1 files changed, 35 insertions, 2 deletions

diff --git a/degesch.c b/degesch.c
index b66114b..5d1186c 100644
--- a/degesch.c
+++ b/degesch.c
@@ -8173,8 +8173,38 @@ lua_plugin_property_get (lua_State *L)
 		return 1;
 	}
 
-	return luaL_error (L, "%s: %s",
-		"no such method or property", property_name);
+	// Or we look for a property set by the user (__gc cannot be overriden)
+	if (lua_getuservalue (L, 1) != LUA_TTABLE)
+		lua_pushnil (L);
+	else
+		lua_getfield (L, -1, property_name);
+	return 1;
+}
+
+static int
+lua_plugin_property_set (lua_State *L)
+{
+	luaL_checktype (L, 1, LUA_TUSERDATA);
+	const char *property_name = luaL_checkstring (L, 2);
+	luaL_checkany (L, 3);
+
+	// We use the associated value to store user-defined properties
+	int type = lua_getuservalue (L, 1);
+	if (type == LUA_TNIL)
+	{
+		lua_pop (L, 1);
+		lua_newtable (L);
+		lua_pushvalue (L, -1);
+		lua_setuservalue (L, 1);
+	}
+	else if (type != LUA_TTABLE)
+		return luaL_error (L, "associated value is not a table");
+
+	// Beware that we do not check for conflicts here;
+	// if Lua code writes a conflicting field, it is effectively ignored
+	lua_pushvalue (L, 3);
+	lua_setfield (L, -2, property_name);
+	return 0;
 }
 
 static void
@@ -8186,6 +8216,9 @@ lua_plugin_create_meta (lua_State *L, const char *name, luaL_Reg *fns)
 	// Emulate properties for convenience
 	lua_pushcfunction (L, lua_plugin_property_get);
 	lua_setfield (L, -2, "__index");
+	lua_pushcfunction (L, lua_plugin_property_set);
+	lua_setfield (L, -2, "__newindex");
+
 	lua_pop (L, 1);
 }