Add VALIDATE_LUA as a function in lpxserver and lpxclient

luprex/cpp/core/lpxserver.cpp

@@ -6,6 +6,7 @@
 #include "luaconsole.hpp"
 #include "util.hpp"
 #include "printbuffer.hpp"
+#include "luastack.hpp"
 
 #include <memory>
 
@@ -33,10 +34,14 @@ public:
     eng::vector<Invocation> delayed_invocations_;
     int64_t admin_id_ = 0;
     double next_tick_ = 0;
+    lua_State *lua_syntax_checker_;
 
 public:
     LpxServer()
     {
+        // Create a little lua interpreter for syntax checking only.
+        lua_syntax_checker_ = LuaCoreStack::newstate(eng::l_alloc);
+
         // Create the master world model.
         master_.reset(new World(WORLD_TYPE_MASTER));
 
@@ -62,6 +67,10 @@ public:
         rescan_lua_source(true);
     }
 
+    ~LpxServer() {
+        lua_close(lua_syntax_checker_);
+    }
+
     virtual void do_syntax_error(std::string_view error) override {
         stdostream() << "Syntax error: " << error << std::endl;
     }
@@ -178,6 +187,13 @@ public:
                 master_->rollback();
                 break;
             }
+            case AccessKind::VALIDATE_LUA: {
+                LuaVar closure;
+                LuaDefStack LS(lua_syntax_checker_, closure);
+                eng::string errmsg = LS.load(closure, datapk, "stdin");
+                retpk->write_bytes(errmsg);
+                break;
+            }
             default: {
                 stdostream() << "Invalid event_access: " << int(kind) << std::endl;
             }