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Automatic Error Checking


In this chapter, you will learn how to use a tool called LuaCheck to automatically scan your mod for any mistakes. This tool can be used in combination with your editor to provide alerts to any mistakes.

Installing LuaCheck


Simply download luacheck.exe from the Github Releases page.


First, you’ll need to install LuaRocks:

sudo apt install luarocks

You can then install LuaCheck globally:

sudo luarocks install luacheck

Check that it’s installed with the following command:

luacheck -v

Running LuaCheck

The first time you run LuaCheck, it will probably pick up a lot of false errors. This is because it still needs to be configured.

On Windows, open powershell or bash in the root folder of your project and run path\to\luacheck.exe .

On Linux, run luacheck . whilst in the root folder of your project.

Configuring LuaCheck

Create a file called .luacheckrc in the root of your project. This could be the root of your game, modpack, or mod.

Put the following contents in it:

unused_args = false
allow_defined_top = true

globals = {

read_globals = {
    string = {fields = {"split"}},
    table = {fields = {"copy", "getn"}},

    -- Builtin
    "vector", "ItemStack",
    "dump", "DIR_DELIM", "VoxelArea", "Settings",

    -- MTG
    "default", "sfinv", "creative",

Next, you’ll need to test that it works by running LuaCheck. You should get a lot fewer errors this time. Starting at the first error you get, modify the code to remove the issue, or modify the configuration if the code is correct. See the list below.


  • accessing undefined variable foobar - If foobar is meant to be a global, add it to read_globals. Otherwise, add any missing locals to the mod.
  • setting non-standard global variable foobar - If foobar is meant to be a global, add it to globals. Remove from read_globals if present. Otherwise, add any missing locals to the mod.
  • mutating read-only global variable ‘foobar’ - Move foobar from read_globals to globals, or stop writing to foobar.

Using with editor

It is highly recommended that you find and install a plugin for your editor of choice to show you errors without running a command. Most editors will likely have a plugin available.