LuaCheck: Create chapter

_data/links_en.yml

@@ -81,12 +81,16 @@
 
 - hr: true
 
-- title: Releasing a Mod
+- title: Automatic Error Checking
   num: 18
+  link: chapters/luacheck.html
+
+- title: Releasing a Mod
+  num: 19
   link: chapters/releasing.html
 
 - title: Read More
-  num: 19
+  num: 20
   link: chapters/readmore.html
 
 - hr: true

en/chapters/luacheck.md

@@ -0,0 +1,129 @@
+---
+title: Automatic Error Checking
+layout: default
+root: ../../
+---
+
+## Introduction
+
+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](#installing-luacheck)
+    * [Windows](#windows)
+    * [Linux](#linux)
+* [Running LuaCheck](#running-luacheck)
+* [Configuring LuaCheck](#configuring-luacheck)
+    * [Troubleshooting](#troubleshooting)
+* [Checking commits with Travis](#checking-commits-with-travis)
+
+## Installing LuaCheck
+
+### Windows
+
+Simply download luacheck.exe from
+[the Github Releases page](https://github.com/mpeterv/luacheck/releases).
+
+### Linux
+
+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, the root project folder onto the luacheck.exe executable.
+
+On Linux, run `luacheck .` whilst in the root folder of your project.
+
+## Configuring LuaCheck
+
+Create a file called .luacheck in the root of your project. This could be the
+root of your game, modpack, or mod.
+
+Put the following contents in it:
+
+{% highlight lua %}
+unused_args = false
+allow_defined_top = true
+
+globals = {
+	"minetest",
+}
+
+read_globals = {
+	string = {fields = {"split"}},
+	table = {fields = {"copy", "getn"}},
+	"vector", "default", "ItemStack",
+}
+{% endhighlight %}
+
+Next you'll need to test that it works by running LuaCheck. You should get a lot
+less errors this time. Starting at the first error you get, either modify the
+configuration to take it into account, or if there's a bug then fix it - take
+a look at the below list.
+
+### Troubleshooting
+
+* **accessing undefined variable foobar** - If foobar is meant to be a global,
+  then add it to read_globals. Otherwise add any missing `local`s to the mod.
+* **setting non-standard global variable foobar** - If foobar is meant to be a global,
+  then add it to `globals`. Remove from `read_globals` if present there.
+  Otherwise add any missing `local`s to the mod.
+* **mutating read-only global variable 'foobar'** - Move foobar from `read_globals` to
+  `globals`.
+
+## Checking commits with Travis
+
+If your project is public and is on Github, you can use TravisCI - a free service
+to run jobs on commits to check them. This means that every commit you push will
+be checked against LuaCheck, and a green tick or red cross displayed next to them
+depending on whether LuaCheck finds any mistakes. This is especially helpful for
+when you project receives a pull-request - you'll be able to see the LuaCheck output
+without downloading the code.
+
+First you should visit [travis-ci.org](https://travis-ci.org/) and sign in with
+your Github account. Then find your project's repo in your Travis profile,
+and enable travis by flipping the switch.
+
+Next, create a file called .travis.yml with the following content:
+
+{% highlight yml %}
+language: generic
+sudo: false
+addons:
+  apt:
+    packages:
+    - luarocks
+before_install:
+  - luarocks install --local luacheck
+script:
+- $HOME/.luarocks/bin/luacheck --no-color .
+notifications:
+  email: false
+{% endhighlight %}
+
+If your project is a game rather than a mod or mod pack,
+change the line after `script:` to:
+
+{% highlight yml %}
+- $HOME/.luarocks/bin/luacheck --no-color mods/
+{% endhighlight %}
+
+Now commit and push to Github. Go to your project's page on Github, and click
+commits. You should see an orange disc next to the commit you just made. After
+a while it should change either into a green tick or a red cross depending on the
+outcome of LuaCheck. In either case, you can click the icon to see the build logs
+and the output of LuaCheck.