Add VALIDATE_LUA as a function in lpxserver and lpxclient

luprex/cpp/core/luastack.cpp

@@ -323,6 +323,29 @@ bool LuaCoreStack::next(LuaSlot tab, LuaSlot key, LuaSlot value) const {
     return (ret != 0);
 }
 
+eng::string LuaCoreStack::load(LuaSlot result, std::string_view code, std::string_view context)
+{
+    eng::string fullcontext = eng::string("=") + eng::string(context);
+    luaL_loadbuffer(L_, code.data(), code.size(), fullcontext.c_str());
+    int type = lua_type(L_, -1);
+    if (type == LUA_TFUNCTION) {
+        // compiler returned a closure.
+        lua_replace(L_, result.index());
+        return "";
+    } else if (type == LUA_TSTRING) {
+        // compiler returned an error message.
+        size_t len;
+        const char *str = lua_tolstring(L_, -1, &len);
+        eng::string message(str, len);
+        lua_pop(L_, 1);
+        if (message.empty()) message = "unknown compiler error";
+        set(result, message);
+        return message;
+    } else {
+        assert(false && "lua compiler didn't return a closure, but didn't return an error message either");
+    }
+}
+
 void LuaCoreStack::getglobaltable(LuaSlot target) const {
     lua_pushglobaltable(L_);
     lua_replace(L_, target);