Add luacheck and fix reported warnings

.github/workflows/build.yml

@@ -0,0 +1,11 @@
+on: [push, pull_request]
+name: build
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@master
+      - name: lint
+        uses: Roang-zero1/factorio-mod-luacheck@master
+        with:
+          luacheckrc_url: ""

.luacheckrc

@@ -0,0 +1,23 @@
+max_line_length = 80
+
+globals = {
+    'formspec_ast',
+    'minetest',
+}
+
+read_globals = {
+    string = {fields = {'split', 'trim'}},
+    table = {fields = {'copy'}}
+}
+
+-- The elements.lua file is auto-generated and has a hideously long line which
+-- luacheck complains about.
+files["elements.lua"].ignore = {""}
+
+-- Because formspec_ast supports running outside of MT, some string and table
+-- functions are added in init.lua (unless running in MT).
+files['init.lua'].globals = read_globals
+
+-- This error is thrown for methods that don't use the implicit "self"
+-- parameter.
+ignore = {"212/self"}

core.lua

@@ -83,7 +83,6 @@ local function raw_parse(spec)
         if #inner > 0 then
             table.insert(inner, i)
             table.insert(elem, inner)
-            inner = {}
         else
             table.insert(elem, i)
         end
@@ -204,7 +203,7 @@ types['...'] = function(elems, obj, res)
     local template = {obj}
     local val = {}
     local is_string = type(obj[2]) == 'string'
-    for i, elem in ipairs(elems) do
+    for _, elem in ipairs(elems) do
         local n = parse_value({elem}, template)
         if is_string then
             n = n[obj[1]]
@@ -251,7 +250,7 @@ local function parse_elem(elem, custom_handlers)
     end
 
     local good, ast_elem
-    for i, template in ipairs(data) do
+    for _, template in ipairs(data) do
         if type(template) == 'function' then
             good, ast_elem = pcall(template, elem)
             if good and (not ast_elem or not ast_elem.type) then
@@ -351,7 +350,7 @@ local function unparse_ellipsis(elem, obj1, res, inner)
     elseif type(obj1[2]) == 'string' then
         local value = elem[obj1[1]]
         if value == nil then return end
-        for k, v in ipairs(value) do
+        for _, v in ipairs(value) do
             table.insert(res, tostring(v))
         end
     else
@@ -359,7 +358,7 @@ local function unparse_ellipsis(elem, obj1, res, inner)
         local data = elem[elem.type or 'data'] or elem
         for _, elem2 in ipairs(data) do
             local r = {}
-            for i, obj2 in ipairs(obj1) do
+            for _, obj2 in ipairs(obj1) do
                 if obj2[2] == '...' then
                     unparse_ellipsis(elem2, obj2[1], r, true)
                 elseif type(obj2[2]) == 'string' then
@@ -421,7 +420,7 @@ local function unparse_elem(elem, res, force)
         local err = unparse_elem(elem, res, true)
         if err then return err end
         for _, e in ipairs(elem) do
-            local err = unparse_elem(e, res)
+            err = unparse_elem(e, res)
             if err then return err end
         end
         return unparse_elem({type=elem.type .. '_end'}, res, true)
@@ -434,7 +433,7 @@ local function unparse_elem(elem, res, force)
 
     local good, raw_elem
     local possible_elems = {}
-    for i, template in ipairs(data) do
+    for _, template in ipairs(data) do
         if type(template) == 'function' then
             good, raw_elem = false, 'Unknown element.'
         else
@@ -520,7 +519,7 @@ function parse_mt:__index(key)
             return func(obj or '')
         end
     else
-        return function(obj)
+        return function(_)
             error('Unknown element type: ' .. tostring(key))
         end
     end

helpers.lua

@@ -137,9 +137,9 @@ function formspec_ast.show_formspec(player, formname, formspec)
         return 'No such player!'
     end
 
-    local formspec, err = formspec_ast.interpret(formspec)
-    if formspec then
-        minetest.show_formspec(player, formname, formspec)
+    local new_fs, err = formspec_ast.interpret(formspec)
+    if new_fs then
+        minetest.show_formspec(player, formname, new_fs)
     else
         minetest.log('warning', 'formspec_ast.show_formspec(): ' ..
             tostring(err))
@@ -166,7 +166,7 @@ formspec_ast.register_element('formspec_ast:centered_label', function(raw,
             y = 0,
             w = parse.number(raw[2][1]),
             h = parse.number(raw[2][2]),
-            texture_name = '',
+            texture_name = 'blank.png',
             name = '',
             label = parse.string(raw[3]),
             noclip = true,
@@ -193,7 +193,7 @@ formspec_ast.register_element('formspec_ast:centered_label', function(raw,
 end)
 
 -- Add a formspec element to crash clients
-formspec_ast.register_element('formspec_ast:crash', function(raw, parse)
+formspec_ast.register_element('formspec_ast:crash', function(_, _)
     return {
         type = 'list',
         inventory_location = '___die',

safety.lua

@@ -186,8 +186,8 @@ function formspec_ast.safe_parse(tree, custom_handlers)
 
     -- Iterate over the tree and add valid elements to a new table.
     local res = {formspec_version = tree.formspec_version}
-    for i, elem in ipairs(tree) do
-        local good, msg = pcall(validate_elem, elem)
+    for _, elem in ipairs(tree) do
+        local good, _ = pcall(validate_elem, elem)
         if good then
             res[#res + 1] = elem
         end