Run Luacheck in CI & fix reported errors (#1285)

Tried to do this as non-intrusively as possible, mostly by ignoring the
issues in-line.

Set the option unused_secondaries to false as suggested by @hishamhm.
This makes named but ununsed return values, that serves a documenting
purpose, allowed.

21 files changed, 40 insertions, 33 deletions

diff --git a/src/luarocks/build.lua b/src/luarocks/build.lua
index 0e8e7f58..ae529856 100644
--- a/src/luarocks/build.lua
+++ b/src/luarocks/build.lua
@@ -94,7 +94,7 @@ local function check_macosx_deployment_target(rockspec)
       local version = util.popen_read("sw_vers -productVersion")
       if version:match("^%d+%.%d+%.%d+$") or version:match("^%d+%.%d+$") then
          if vers.compare_versions(target, version) then
-            return nil, ("This rock requires Mac OSX %s, and you are running %s."):format(targetversion, version)
+            return nil, ("This rock requires Mac OSX %s, and you are running %s."):format(target, version)
          end
       end
       patch_variable("CC")
diff --git a/src/luarocks/build/builtin.lua b/src/luarocks/build/builtin.lua
index 70651ce8..6241c718 100644
--- a/src/luarocks/build/builtin.lua
+++ b/src/luarocks/build/builtin.lua
@@ -252,7 +252,7 @@ function builtin.run(rockspec, no_install)
          end
          return execute(variables.LD.." "..variables.LIBFLAG, "-o", library, unpack(extras))
       end
-      compile_static_library = function(library, objects, libraries, libdirs, name)
+      compile_static_library = function(library, objects, libraries, libdirs, name)  -- luacheck: ignore 211
          local ok = execute(variables.AR, "rc", library, unpack(objects))
          if ok then
             ok = execute(variables.RANLIB, library)
diff --git a/src/luarocks/cmd.lua b/src/luarocks/cmd.lua
index c8bcb552..21f35e20 100644
--- a/src/luarocks/cmd.lua
+++ b/src/luarocks/cmd.lua
@@ -337,7 +337,7 @@ local function use_to_fix_location(key)
    return buf
 end
 
-local function get_config_text(cfg)
+local function get_config_text(cfg)  -- luacheck: ignore 431
    local deps = require("luarocks.deps")
 
    local libdir_ok = deps.check_lua_libdir(cfg.variables)
diff --git a/src/luarocks/cmd/build.lua b/src/luarocks/cmd/build.lua
index 31622f35..d1fccfdd 100644
--- a/src/luarocks/cmd/build.lua
+++ b/src/luarocks/cmd/build.lua
@@ -18,7 +18,7 @@ local make = require("luarocks.cmd.make")
 local cmd = require("luarocks.cmd")
 
 function cmd_build.add_to_parser(parser)
-   local cmd = parser:command("build", "Build and install a rock, compiling its C parts if any.\n"..
+   local cmd = parser:command("build", "Build and install a rock, compiling its C parts if any.\n"..  -- luacheck: ignore 431
       "If the sources contain a luarocks.lock file, uses it as an authoritative source for "..
       "exact version of dependencies.\n"..
       "If no arguments are given, behaves as luarocks make.", util.see_also())
diff --git a/src/luarocks/cmd/doc.lua b/src/luarocks/cmd/doc.lua
index 6345063d..2ab7e43c 100644
--- a/src/luarocks/cmd/doc.lua
+++ b/src/luarocks/cmd/doc.lua
@@ -66,7 +66,7 @@ function doc.command(args)
       util.printout(rock.." is not installed. Looking for it in the rocks servers...")
       return try_to_open_homepage(args.rock, args.namespace, args.version)
    end
-   name, version = iname, iversion
+   local name, version = iname, iversion
    
    local rockspec, err = fetch.load_local_rockspec(path.rockspec_file(name, version, repo))
    if not rockspec then return nil,err end
diff --git a/src/luarocks/cmd/install.lua b/src/luarocks/cmd/install.lua
index 1fa15453..760649b0 100644
--- a/src/luarocks/cmd/install.lua
+++ b/src/luarocks/cmd/install.lua
@@ -14,10 +14,9 @@ local search = require("luarocks.search")
 local queries = require("luarocks.queries")
 local cfg = require("luarocks.core.cfg")
 local cmd = require("luarocks.cmd")
-local dir = require("luarocks.dir")
 
 function install.add_to_parser(parser)
-   local cmd = parser:command("install", "Install a rock.", util.see_also())
+   local cmd = parser:command("install", "Install a rock.", util.see_also())  -- luacheck: ignore 431
 
    cmd:argument("rock", "The name of a rock to be fetched from a repository "..
       "or a filename of a locally available rock.")
diff --git a/src/luarocks/cmd/make.lua b/src/luarocks/cmd/make.lua
index 78647b63..a72e6817 100644
--- a/src/luarocks/cmd/make.lua
+++ b/src/luarocks/cmd/make.lua
@@ -13,7 +13,6 @@ local fetch = require("luarocks.fetch")
 local pack = require("luarocks.pack")
 local remove = require("luarocks.remove")
 local deps = require("luarocks.deps")
-local deplocks = require("luarocks.deplocks")
 local writer = require("luarocks.manif.writer")
 local cmd = require("luarocks.cmd")
 
@@ -47,6 +46,7 @@ function make.cmd_options(parser)
 end
 
 function make.add_to_parser(parser)
+   -- luacheck: push ignore 431
    local cmd = parser:command("make", [[
 Builds sources in the current directory, but unlike "build", it does not fetch
 sources, etc., assuming everything is available in the current directory. If no
@@ -65,6 +65,7 @@ authoritative source for exact version of dependencies. The --pin flag
 overrides and recreates this file scanning dependency based on ranges.
 ]], util.see_also())
       :summary("Compile package in current directory using a rockspec.")
+   -- luacheck: pop
 
    cmd:argument("rockspec", "Rockspec for the rock to build.")
       :args("?")
@@ -117,7 +118,7 @@ function make.command(args)
       return build.build_rockspec(rockspec, opts)
    elseif args.pack_binary_rock then
       return pack.pack_binary_rock(name, namespace, rockspec.version, args.sign, function()
-         local name, version = build.build_rockspec(rockspec, opts)
+         local name, version = build.build_rockspec(rockspec, opts)  -- luacheck: ignore 431
          if name and args.no_doc then
             util.remove_doc_dir(name, version)
          end
@@ -128,7 +129,7 @@ function make.command(args)
       if not ok then return nil, err, cmd.errorcodes.PERMISSIONDENIED end
       ok, err = build.build_rockspec(rockspec, opts)
       if not ok then return nil, err end
-      local name, version = ok, err
+      local name, version = ok, err  -- luacheck: ignore 421
 
       if opts.build_only_deps then
          util.printout("Stopping after installing dependencies for " ..name.." "..version)
diff --git a/src/luarocks/cmd/pack.lua b/src/luarocks/cmd/pack.lua
index 9ceb2fa8..29a43e7b 100644
--- a/src/luarocks/cmd/pack.lua
+++ b/src/luarocks/cmd/pack.lua
@@ -5,7 +5,6 @@ local cmd_pack = {}
 
 local util = require("luarocks.util")
 local pack = require("luarocks.pack")
-local signing = require("luarocks.signing")
 local queries = require("luarocks.queries")
 
 function cmd_pack.add_to_parser(parser)
diff --git a/src/luarocks/cmd/purge.lua b/src/luarocks/cmd/purge.lua
index b71baa7c..fa4be4d7 100644
--- a/src/luarocks/cmd/purge.lua
+++ b/src/luarocks/cmd/purge.lua
@@ -16,6 +16,7 @@ local queries = require("luarocks.queries")
 local cmd = require("luarocks.cmd")
 
 function purge.add_to_parser(parser)
+   -- luacheck: push ignore 431
    local cmd = parser:command("purge", [[
 This command removes rocks en masse from a given tree.
 By default, it removes all rocks from a tree.
@@ -23,6 +24,7 @@ By default, it removes all rocks from a tree.
 The --tree option is mandatory: luarocks purge does not assume a default tree.]],
    util.see_also())
       :summary("Remove all installed rocks from a tree.")
+   -- luacheck: pop
 
    cmd:flag("--old-versions", "Keep the highest-numbered version of each "..
       "rock and remove the other ones. By default it only removes old "..
diff --git a/src/luarocks/cmd/remove.lua b/src/luarocks/cmd/remove.lua
index cede148d..46f3e4a6 100644
--- a/src/luarocks/cmd/remove.lua
+++ b/src/luarocks/cmd/remove.lua
@@ -15,6 +15,7 @@ local queries = require("luarocks.queries")
 local cmd = require("luarocks.cmd")
 
 function cmd_remove.add_to_parser(parser)
+   -- luacheck: push ignore 431
    local cmd = parser:command("remove", [[
 Uninstall a rock.
 
@@ -23,6 +24,7 @@ Will only perform the removal if it does not break dependencies.
 To override this check and force the removal, use --force or --force-fast.]],
    util.see_also())
       :summary("Uninstall a rock.")
+   -- luacheck: pop
 
    cmd:argument("rock", "Name of the rock to be uninstalled.")
       :action(util.namespaced_name_action)
diff --git a/src/luarocks/cmd/which.lua b/src/luarocks/cmd/which.lua
index 9a363e85..7503df00 100644
--- a/src/luarocks/cmd/which.lua
+++ b/src/luarocks/cmd/which.lua
@@ -32,7 +32,7 @@ function which_cmd.command(args)
    local modpath = args.modname:gsub("%.", "/")
    for _, v in ipairs({"path", "cpath"}) do
       for p in package[v]:gmatch("([^;]+)") do
-         local pathname = p:gsub("%?", modpath)
+         local pathname = p:gsub("%?", modpath)  -- luacheck: ignore 421
          if fs.exists(pathname) then
             util.printout(pathname)
             util.printout("(found directly via package." .. v .. " -- not installed as a rock?)")
diff --git a/src/luarocks/core/cfg.lua b/src/luarocks/core/cfg.lua
index 4ac5ee28..d65681c1 100644
--- a/src/luarocks/core/cfg.lua
+++ b/src/luarocks/core/cfg.lua
@@ -10,8 +10,8 @@
 -- files. Run `luarocks` with no arguments to see the locations of
 -- these files in your platform.
 
-local next, table, pairs, require, os, pcall, ipairs, package, tonumber, type, assert =
-      next, table, pairs, require, os, pcall, ipairs, package, tonumber, type, assert
+local table, pairs, require, os, pcall, ipairs, package, type, assert =
+      table, pairs, require, os, pcall, ipairs, package, type, assert
 
 local util = require("luarocks.core.util")
 local persist = require("luarocks.core.persist")
diff --git a/src/luarocks/download.lua b/src/luarocks/download.lua
index 70570344..1246e498 100644
--- a/src/luarocks/download.lua
+++ b/src/luarocks/download.lua
@@ -32,8 +32,8 @@ function download.download(arch, name, namespace, version, all, check_lua_versio
       local has_result = false
       local all_ok = true
       local any_err = ""
-      for name, result in pairs(results) do
-         for version, items in pairs(result) do
+      for name, result in pairs(results) do  -- luacheck: ignore 422
+         for version, items in pairs(result) do  -- luacheck: ignore 422
             for _, item in ipairs(items) do
                -- Ignore provided rocks.
                if item.arch ~= "installed" then
diff --git a/src/luarocks/fs.lua b/src/luarocks/fs.lua
index bd1a96a2..ecfc5a28 100644
--- a/src/luarocks/fs.lua
+++ b/src/luarocks/fs.lua
@@ -29,6 +29,7 @@ do
 
       if old_popen or old_execute then return end
       old_popen = io.popen
+      -- luacheck: push globals io os
       io.popen = function(one, two)
          if two == nil then
             print("\nio.popen: ", one)
@@ -49,6 +50,7 @@ do
          end
          return unpack(code, 1, code.n)
       end
+      -- luacheck: pop
    end
 end
 
diff --git a/src/luarocks/fs/lua.lua b/src/luarocks/fs/lua.lua
index b9b36447..83ffbd47 100644
--- a/src/luarocks/fs/lua.lua
+++ b/src/luarocks/fs/lua.lua
@@ -215,7 +215,7 @@ function fs_lua.modules(at)
 
    local modules = {}
    local is_duplicate = {}
-   for _, path in ipairs(paths) do
+   for _, path in ipairs(paths) do  -- luacheck: ignore 421
       local files = fs.list_dir(path)
       for _, filename in ipairs(files or {}) do
          if filename:match("%.[lL][uU][aA]$") then
@@ -705,7 +705,7 @@ local redirect_protocols = {
    https = luasec_ok and https,
 }
 
-local function request(url, method, http, loop_control)
+local function request(url, method, http, loop_control)  -- luacheck: ignore 431
    local result = {}
    
    if cfg.verbose then
@@ -805,7 +805,7 @@ end
 -- via the HTTP Last-Modified header if the full download is needed.
 -- @return (boolean | (nil, string, string?)): True if successful, or
 -- nil, error message and optionally HTTPS error in case of errors.
-local function http_request(url, filename, http, cache)
+local function http_request(url, filename, http, cache)  -- luacheck: ignore 431
    if cache then
       local status = read_timestamp(filename..".status")
       local timestamp = read_timestamp(filename..".timestamp")
@@ -824,7 +824,7 @@ local function http_request(url, filename, http, cache)
             end
          end
 
-         local result, status, headers, err = request(url, "HEAD", http)
+         local result, status, headers, err = request(url, "HEAD", http)  -- luacheck: ignore 421
          if not result then
             return fail_with_status(filename, status, headers)
          end
diff --git a/src/luarocks/fs/win32.lua b/src/luarocks/fs/win32.lua
index 8ae62cf0..00dd0163 100644
--- a/src/luarocks/fs/win32.lua
+++ b/src/luarocks/fs/win32.lua
@@ -15,8 +15,11 @@ local util = require("luarocks.util")
 -- See http://lua-users.org/lists/lua-l/2013-11/msg00367.html
 local _prefix = "type NUL && "
 local _popen, _execute = io.popen, os.execute
+
+-- luacheck: push globals io os
 io.popen = function(cmd, ...) return _popen(_prefix..cmd, ...) end
 os.execute = function(cmd, ...) return _execute(_prefix..cmd, ...) end
+-- luacheck: pop
 
 --- Annotate command string for quiet execution.
 -- @param cmd string: A command-line string.
@@ -38,7 +41,7 @@ end
 local function split_root(pathname)
    local drive = ""
    local root = ""
-   local rest = ""
+   local rest
 
    local unquoted = pathname:match("^['\"](.*)['\"]$")
    if unquoted then
diff --git a/src/luarocks/fs/win32/tools.lua b/src/luarocks/fs/win32/tools.lua
index 57e8c80e..d6202ab9 100644
--- a/src/luarocks/fs/win32/tools.lua
+++ b/src/luarocks/fs/win32/tools.lua
@@ -21,11 +21,11 @@ function tools.command_at(directory, cmd, exit_on_error)
    if exit_on_error then
       op = " && "
    end
-   local cmd = "cd " .. fs.Q(directory) .. op .. cmd
+   local cmd_prefixed = "cd " .. fs.Q(directory) .. op .. cmd
    if drive then
-      cmd = drive .. " & " .. cmd
+      cmd_prefixed = drive .. " & " .. cmd_prefixed
    end
-   return cmd
+   return cmd_prefixed
 end
 
 --- Create a directory if it does not already exist.
diff --git a/src/luarocks/loader.lua b/src/luarocks/loader.lua
index 5aa84632..a3bd8f1b 100644
--- a/src/luarocks/loader.lua
+++ b/src/luarocks/loader.lua
@@ -1,10 +1,12 @@
-
 --- A module which installs a Lua package loader that is LuaRocks-aware.
 -- This loader uses dependency information from the LuaRocks tree to load
 -- correct versions of modules. It does this by constructing a "context"
 -- table in the environment, which records which versions of packages were
 -- used to load previous modules, so that the loader chooses versions
 -- that are declared to be compatible with the ones loaded earlier.
+
+-- luacheck: globals luarocks
+
 local loaders = package.loaders or package.searchers
 local require, ipairs, table, type, next, tostring, error =
       require, ipairs, table, type, next, tostring, error
@@ -24,7 +26,7 @@ end
 local path = require("luarocks.core.path")
 local manif = require("luarocks.core.manif")
 local vers = require("luarocks.core.vers")
-local require = nil
+local require = nil  -- luacheck: ignore 411
 --------------------------------------------------------------------------------
 
 -- Workaround for wrappers produced by older versions of LuaRocks
diff --git a/src/luarocks/manif/writer.lua b/src/luarocks/manif/writer.lua
index 8c6e4505..8e07702c 100644
--- a/src/luarocks/manif/writer.lua
+++ b/src/luarocks/manif/writer.lua
@@ -30,7 +30,7 @@ local function store_package_items(storage, name, version, items)
 
    local package_identifier = name.."/"..version
 
-   for item_name, path in pairs(items) do
+   for item_name, path in pairs(items) do  -- luacheck: ignore 431
       if not storage[item_name] then
          storage[item_name] = {}
       end
@@ -54,7 +54,7 @@ local function remove_package_items(storage, name, version, items)
 
    local package_identifier = name.."/"..version
 
-   for item_name, path in pairs(items) do
+   for item_name, path in pairs(items) do  -- luacheck: ignore 431
       local all_identifiers = storage[item_name]
 
       for i, identifier in ipairs(all_identifiers) do
diff --git a/src/luarocks/repos.lua b/src/luarocks/repos.lua
index b2a7d81a..4a78dfb2 100644
--- a/src/luarocks/repos.lua
+++ b/src/luarocks/repos.lua
@@ -9,9 +9,8 @@ local util = require("luarocks.util")
 local dir = require("luarocks.dir")
 local manif = require("luarocks.manif")
 local vers = require("luarocks.core.vers")
-local E = {}
 
-local unpack = unpack or table.unpack
+local unpack = unpack or table.unpack  -- luacheck: ignore 211
 
 --- Get type and name of an item (a module or a command) provided by a file.
 -- @param deploy_type string: rock manifest subtree the file comes from ("bin", "lua", or "lib").
@@ -77,7 +76,7 @@ function repos.recurse_rock_manifest_entry(entry, action)
 
       for file, sub in pairs(tree) do
          local sub_path = (parent_path and (parent_path .. "/") or "") .. file
-         local ok, err
+         local ok, err  -- luacheck: ignore 231
 
          if type(sub) == "table" then
             ok, err = do_recurse_rock_manifest_entry(sub, sub_path)
diff --git a/src/luarocks/tools/zip.lua b/src/luarocks/tools/zip.lua
index fb27456d..37091185 100644
--- a/src/luarocks/tools/zip.lua
+++ b/src/luarocks/tools/zip.lua
@@ -10,8 +10,6 @@ local dir = require("luarocks.dir")
 
 local pack = table.pack or function(...) return { n = select("#", ...), ... } end
 
-local stat_ok, stat = pcall(require, "posix.sys.stat")
-
 local function shr(n, m)
    return math.floor(n / 2^m)
 end