MetaDataRef: Add contains() and get() (#7214)

doc/lua_api.txt

@@ -3909,12 +3909,15 @@ An interface to use mod channels on client and server
 See `StorageRef`, `NodeMetaRef`, `ItemStackMetaRef`, and `PlayerMetaRef`.
 
 #### Methods
-* `set_string(name, value)`
-* `get_string(name)`
-* `set_int(name, value)`
-* `get_int(name)`
-* `set_float(name, value)`
-* `get_float(name)`
+* `contains(key)`: Returns true if key present, otherwise false.
+    * Returns `nil` when the MetaData is inexistent.
+* `get(key)`: Returns `nil` if key not present, else the stored string.
+* `set_string(key, value)`: Value of `""` will delete the key.
+* `get_string(key)`: Returns `""` if key not present.
+* `set_int(key, value)`
+* `get_int(key)`: Returns `0` if key not present.
+* `set_float(key, value)`
+* `get_float(key)`: Returns `0` if key not present.
 * `to_table()`: returns `nil` or a table with keys:
     * `fields`: key-value storage
     * `inventory`: `{list1 = {}, ...}}` (NodeMetaRef only)

games/minimal/mods/test/init.lua

@@ -43,21 +43,32 @@ end)
 local function run_player_meta_tests(player)
 	local meta = player:get_meta()
 	meta:set_string("foo", "bar")
+	assert(meta:contains("foo"))
 	assert(meta:get_string("foo") == "bar")
+	assert(meta:get("foo") == "bar")
 
 	local meta2 = player:get_meta()
 	assert(meta2:get_string("foo") == "bar")
+	assert(meta2:get("foo") == "bar")
 	assert(meta:equals(meta2))
 	assert(player:get_attribute("foo") == "bar")
 
 	meta:set_string("bob", "dillan")
 	assert(meta:get_string("foo") == "bar")
 	assert(meta:get_string("bob") == "dillan")
+	assert(meta:get("bob") == "dillan")
 	assert(meta2:get_string("foo") == "bar")
 	assert(meta2:get_string("bob") == "dillan")
+	assert(meta2:get("bob") == "dillan")
 	assert(meta:equals(meta2))
 	assert(player:get_attribute("foo") == "bar")
 	assert(player:get_attribute("bob") == "dillan")
+
+	meta:set_string("foo", "")
+	assert(not meta:contains("foo"))
+	assert(meta:get("foo") == nil)
+	assert(meta:get_string("foo") == "")
+	assert(meta:equals(meta2))
 end
 
 local function run_player_tests(player)

src/script/lua_api/l_itemstackmeta.cpp

@@ -123,6 +123,8 @@ void ItemStackMetaRef::Register(lua_State *L)
 
 const char ItemStackMetaRef::className[] = "ItemStackMetaRef";
 const luaL_Reg ItemStackMetaRef::methods[] = {
+	luamethod(MetaDataRef, contains),
+	luamethod(MetaDataRef, get),
 	luamethod(MetaDataRef, get_string),
 	luamethod(MetaDataRef, set_string),
 	luamethod(MetaDataRef, get_int),

src/script/lua_api/l_metadata.cpp

@@ -51,6 +51,42 @@ MetaDataRef* MetaDataRef::checkobject(lua_State *L, int narg)
 
 // Exported functions
 
+// contains(self, name)
+int MetaDataRef::l_contains(lua_State *L)
+{
+	MAP_LOCK_REQUIRED;
+
+	MetaDataRef *ref = checkobject(L, 1);
+	std::string name = luaL_checkstring(L, 2);
+
+	Metadata *meta = ref->getmeta(false);
+	if (meta == NULL)
+		return 0;
+
+	lua_pushboolean(L, meta->contains(name));
+	return 1;
+}
+
+// get(self, name)
+int MetaDataRef::l_get(lua_State *L)
+{
+	MAP_LOCK_REQUIRED;
+
+	MetaDataRef *ref = checkobject(L, 1);
+	std::string name = luaL_checkstring(L, 2);
+
+	Metadata *meta = ref->getmeta(false);
+	if (meta == NULL)
+		return 0;
+
+	std::string str;
+	if (meta->getStringToRef(name, str)) {
+		lua_pushlstring(L, str.c_str(), str.size());
+		return 1;
+	}
+	return 0;
+}
+
 // get_string(self, name)
 int MetaDataRef::l_get_string(lua_State *L)
 {

src/script/lua_api/l_metadata.h

@@ -46,6 +46,12 @@ protected:
 
 	// Exported functions
 
+	// contains(self, name)
+	static int l_contains(lua_State *L);
+
+	// get(self, name)
+	static int l_get(lua_State *L);
+
 	// get_string(self, name)
 	static int l_get_string(lua_State *L);
 

src/script/lua_api/l_nodemeta.cpp

@@ -242,6 +242,8 @@ void NodeMetaRef::Register(lua_State *L)
 
 
 const luaL_Reg NodeMetaRef::methodsServer[] = {
+	luamethod(MetaDataRef, contains),
+	luamethod(MetaDataRef, get),
 	luamethod(MetaDataRef, get_string),
 	luamethod(MetaDataRef, set_string),
 	luamethod(MetaDataRef, get_int),
@@ -266,6 +268,8 @@ void NodeMetaRef::RegisterClient(lua_State *L)
 
 
 const luaL_Reg NodeMetaRef::methodsClient[] = {
+	luamethod(MetaDataRef, contains),
+	luamethod(MetaDataRef, get),
 	luamethod(MetaDataRef, get_string),
 	luamethod(MetaDataRef, get_int),
 	luamethod(MetaDataRef, get_float),

src/script/lua_api/l_playermeta.cpp

@@ -107,6 +107,8 @@ void PlayerMetaRef::Register(lua_State *L)
 // clang-format off
 const char PlayerMetaRef::className[] = "PlayerMetaRef";
 const luaL_Reg PlayerMetaRef::methods[] = {
+	luamethod(MetaDataRef, contains),
+	luamethod(MetaDataRef, get),
 	luamethod(MetaDataRef, get_string),
 	luamethod(MetaDataRef, set_string),
 	luamethod(MetaDataRef, get_int),

src/script/lua_api/l_storage.cpp

@@ -134,6 +134,8 @@ void StorageRef::clearMeta()
 
 const char StorageRef::className[] = "StorageRef";
 const luaL_Reg StorageRef::methods[] = {
+	luamethod(MetaDataRef, contains),
+	luamethod(MetaDataRef, get),
 	luamethod(MetaDataRef, get_string),
 	luamethod(MetaDataRef, set_string),
 	luamethod(MetaDataRef, get_int),