CI: add lua lint check

We now have our first lua script so we should start checking that for
obvious problems

.github/workflows/vader.yml

@@ -22,6 +22,7 @@ jobs:
         run: pip install --pre vim-vint
       - name: Lint vimscript files
         run: vint --warning --enable-neovim ./after ./autoload ./compiler ./ftdetect ./ftplugin ./indent ./syntax
+      - uses: lunarmodules/luacheck@v1
       - uses: ludeeus/action-shellcheck@master
 
   tests:

.luacheckrc

@@ -0,0 +1,20 @@
+-- vim: ft=lua tw=80
+
+-- Global objects defined by the C code
+read_globals = {
+    vim = {
+        filetype = {
+            fields = {
+                add = {},
+                match = {},
+            }
+        },
+        b = {
+            fields = {
+                epuppet_subtype = {
+                    read_only=false,
+                }
+            }
+        }
+    }
+}

ftdetect/puppet.lua

@@ -5,8 +5,8 @@ vim.filetype.add({
     extension = {
         epp =
             function(path, bufnr)
-                path_wo_epp = path:sub(1,-5)
-                matched = vim.filetype.match({ buf = bufnr, filename = path_wo_epp })
+                local path_wo_epp = path:sub(1,-5)
+                local matched = vim.filetype.match({ buf = bufnr, filename = path_wo_epp })
                 if matched ~= nil and matched ~= 'mason' then
                     vim.b.epuppet_subtype = matched
                 end