Add Luacheck integration

- Add CMake target that runs Luacheck - make luacheck
- Add GH Actions workflow with Luacheck
- Fixed warnings found by Luacheck

Luacheck configuration file mostly based on recommendations from Lua
style guide [1].

1. https://www.tarantool.io/en/doc/latest/dev_guide/lua_style_guide/#luacheck

Closes #75

Author: ligurio

.github/workflows/check.yaml

@@ -0,0 +1,27 @@
+name: Static analysis
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  check:
+    if: |
+      github.event_name == 'push' ||
+      github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name != github.repository
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Tarantool
+      uses: tarantool/setup-tarantool@v1
+      with:
+        tarantool-version: '2.8'
+
+    - name: Setup luacheck
+      run: tarantoolctl rocks install luacheck 0.25.0
+
+    - run: cmake -S . -B build
+
+    - name: Run luacheck
+      run: make -C build luacheck

.luacheckrc

@@ -0,0 +1,31 @@
+std = "luajit"
+globals = {
+    "box",
+}
+ignore = {
+    -- Accessing an undefined field of a global variable <package>.
+    "143/package",
+    -- Unused argument <self>.
+    "212/self",
+    -- Redefining a local variable.
+    "411",
+    -- Redefining an argument.
+    "412",
+    -- Shadowing a local variable.
+    "421",
+    -- Shadowing an upvalue.
+    "431",
+    -- Shadowing an upvalue argument.
+    "432",
+}
+
+include_files = {
+    "**/*.lua",
+}
+
+exclude_files = {
+    "build/**/*.lua",
+    "test-run/**/*.lua",
+    ".rocks/**/*.lua",
+    ".git/**/*.lua",
+}

CMakeLists.txt

@@ -9,6 +9,7 @@ endif()
 set(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
 
 # Find Tarantool and Lua dependecies
+find_package(LuaCheck)
 set(TARANTOOL_FIND_REQUIRED ON)
 find_package(Tarantool)
 find_package(CyrusSASL)
@@ -85,3 +86,8 @@ if(POLICY CMP0037)
     cmake_policy(SET CMP0037 OLD) # don't blame `test` target name
 endif(POLICY CMP0037)
 add_subdirectory(test)
+
+add_custom_target(luacheck
+  COMMAND ${LUACHECK} ${PROJECT_SOURCE_DIR}
+  WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+)

README.md

@@ -1,6 +1,7 @@
 <a href="http://tarantool.org">
   <img src="https://avatars2.githubusercontent.com/u/2344919?v=2&s=250" align="right">
 </a>
+[![Static analysis](https://github.com/tarantool/memcached/actions/workflows/check.yaml/badge.svg)](https://github.com/tarantool/memcached/actions/workflows/check.yaml)
 [![Testing](https://github.com/tarantool/memcached/actions/workflows/testing.yaml/badge.svg)](https://github.com/tarantool/memcached/actions/workflows/testing.yaml)
 
 # memcached

cmake/FindLuaCheck.cmake

@@ -0,0 +1,12 @@
+find_program(LUACHECK luacheck
+    HINTS .rocks/
+    PATH_SUFFIXES bin
+    DOC "Lua linter"
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(LuaCheck
+    REQUIRED_VARS LUACHECK
+)
+
+mark_as_advanced(LUACHECK)

memcached/init.lua

@@ -89,15 +89,15 @@ void   memcached_handler   (struct memcached_service *p, int fd);
 int    memcached_setsockopt(int fd, const char *family, const char *type);
 ]]
 
-function startswith(str, start)
+local function startswith(str, start)
        return string.sub(str, 1, string.len(start)) == start
 end
 
 local typetable = {
     name = {
         'string',
         function () return 'memcached' end,
-        function (x) return true end,
+        function (_) return true end,
         [[Name of memcached instance]]
     },
     uri = {
@@ -115,7 +115,7 @@ local typetable = {
     expire_enabled = {
         'boolean',
         function() return true end,
-        function(x) return true end,
+        function() return true end,
         [[configure availability of expiration daemon]]
     },
     expire_items_per_iter = {
@@ -217,6 +217,9 @@ local function config_initial(cfg)
     box.error{ reason = err }
 end
 
+-- TODO: This function is unused, but I see a good idea behind it: show
+-- available options and its default values. Perhaps someday we will use it.
+-- luacheck: no unused
 local function config_help()
     for k, v in pairs(typetable) do
         log.info('%s: %s', k, v[4])
@@ -310,14 +313,14 @@ local memcached_methods = {
         if (self.listener ~= nil) then
             self.listener:close()
         end
-        local rc = memcached_internal.memcached_stop(self.service)
+        memcached_internal.memcached_stop(self.service)
         self.status = STOPPED
         return self
     end,
     info = function (self)
         local stats = memcached_internal.memcached_get_stat(self.service)
         local retval = {}
-        for k, v in pairs(stat_table) do
+        for _, v in pairs(stat_table) do
             retval[v] = stats[0][v]
         end
         return retval

test/bench/memcached.lua

@@ -8,7 +8,7 @@ box.cfg{
 
 package.cpath = './?.so;' .. package.cpath
 
-local inst = require('memcached').create('memcached', '0.0.0.0:11211', {
+require('memcached').create('memcached', '0.0.0.0:11211', {
     expire_full_scan_time = 120
 })
 

test/binary/binary.lua

@@ -7,7 +7,7 @@ box.cfg{
 
 package.cpath = './?.so;' .. package.cpath
 
-local inst = require('memcached').create('memcached',
+require('memcached').create('memcached',
     os.getenv('LISTEN'):match(':(.*)'), {
         expire_full_scan_time = 1,
 })

test/capable/capable.lua

@@ -7,7 +7,7 @@ box.cfg{
 
 package.cpath = './?.so;' .. package.cpath
 
-local inst = require('memcached').create(
+require('memcached').create(
     'memcached',
     os.getenv('LISTEN'):match(':(.*)')
 )

test/sasl/sasl.lua

@@ -5,7 +5,6 @@ package.cpath = './?.so;' .. package.cpath
 --                    Manipulating environment variables                      --
 --------------------------------------------------------------------------------
 local ffi = require('ffi')
-local log = require('log')
 local errno = require('errno')
 
 ffi.cdef[[
@@ -43,7 +42,7 @@ local env = setmetatable({}, {
         return ffi.string(var)
     end,
     __newindex = function(self, key, value)
-        local rv = nil
+        local rv
         if value ~= nil then
             rv = ffi.C.setenv(key, value, 1)
         else
@@ -75,7 +74,7 @@ local memcached = require('memcached')
 local listen_port = env['LISTEN']:match(':(.*)')
 local admin_port  = env['ADMIN']
 
-local inst = memcached.create('memcached', listen_port, {
+memcached.create('memcached', listen_port, {
     expire_full_scan_time = 1,
     sasl = true
 }):grant('guest')