Project: APISIX (Orchestration & Management / API Gateway)
File: CODE_STYLE.md

title: APISIX Lua Coding Style Guide <!-- --> Use 4 spaces as an indent: ```lua --No if a then ngx.say("hello") end ``` ```lua --Yes if a then ngx.say("hello") end ``` You can simplify the operation by changing the tab to 4 spaces in the editor you are using. On both sides of the operator, you need to use a space to separate: ```lua --No local i=1 local s = "apisix" ``` ```lua --Yes local i = 1 local s = "apisix" ``` Many developers will add a semicolon at the end of the line: ```lua --No if a then ngx.say("hello"); end; ``` Adding a semicolon will make the Lua code look ugly and unnecessary. Also, don't want to save the number of lines in the code, the latter turns the multi-line code into one line in order to appear "simple". This will not know when the positioning error is in the end of the code: ```lua --No if a then ngx.say("hello") end ``` ```lua --Yes if a then ngx.say("hello") end ``` The functions needs to be separated by two blank lines: ```lua --No local function foo() end local function bar() end ``` ```lua --Yes local function foo() end local function bar() end ``` If there are multiple if elseif branches, they need a blank line to separate them: ```lua --No if a == 1 then foo() elseif a== 2 then bar() elseif a == 3 then run() else error() end ``` ```lua --Yes if a == 1 then foo() elseif a == 2 then bar() elseif a == 3 then run() else error() end ``` Each line cannot exceed 100 characters. If it exceeds, you need to wrap and align: ```lua --No return limitconnnew("plugin-limit-conn", conf.conn, conf.burst, conf.defaultconndelay) ``` ```lua --Yes return limitconnnew("plugin-limit-conn", conf.conn, conf.burst, conf.defaultconndelay) ``` When the linefeed is aligned, the correspondence between the upper and lower lines should be reflected. For the example above, the parameters of the second line of functions are to the right of the left parenthesis of the first line. If it is a string stitching alignment, you need to put `..` in the next line: ```lua --No return limitconnnew("plugin-limit-conn" .. "plugin-limit-conn" .. "plugin-limit-conn") ``` ```lua --Yes return limitconnnew("plugin-limit-conn" .. "plugin-limit-conn" .. "plugin-limit-conn") ``` ```lua --Yes return "param1", "plugin-limit-conn" .. "plugin-limit-conn" ``` Local variables should always be used, not global variables: ```lua --No i = 1 s = "apisix" ``` ```lua --Yes local i = 1 local s = "apisix" ``` Variable naming uses the `snake_case` style: ```lua --No local IndexArr = 1 local str_Name = "apisix" ``` ```lua --Yes local index_arr = 1 local str_name = "apisix" ``` Use all capitalization for constants: ```lua --No local max_int = 65535 local server_name = "apisix" ``` ```lua --Yes local MAX_INT = 65535 local SERVER_NAME = "apisix" ``` Use `table.new` to pre-allocate the table: ```lua --No local t = {} for i = 1, 100 do t[i] = i end ``` ```lua --Yes local new_tab = require

local t = new_tab(100, 0) for i = 1, 100 do t[i] = i end ``` Don't use `nil` in an array: ```lua --No local t = {1, 2, nil, 3} ``` If you must use null values, use `ngx.null` to indicate: ```lua --Yes local t = {1, 2, ngx.null, 3} ``` Do not splicing strings on the hot code path: ```lua --No local s = "" for i = 1, 100000 do s = s .. "a" end ``` ```lua --Yes local new_tab = require "table.new" local t = new_tab(100000, 0) for i = 1, 100000 do t[i] = "a" end local s = table.concat(t, "") ``` The naming of functions also follows `snake_case`: ```lua --No local function testNginx() end ``` ```lua --Yes local function test_nginx() end ``` The function should return as early as possible: ```lua --No local function check(age, name) local ret = true if age < 20 then ret = false end if name == "a" then ret = false end -- do something else return ret end ``` ```lua --Yes local function check(age, name) if age < 20 then return false end if name == "a" then return false end -- do something else return true end ``` The function should return `<boolean>`, `err`. The first return value means successful or not, if not, the second return value specifies the error message. The error message can be ignored in some cases. ```lua --No local function check() return "failed" end ``` ```lua --Yes local function check() return false, "failed" end ``` All require libraries must be localized: ```lua --No local function foo() local ok, err = ngx.timer.at(delay, handler) end ``` ```lua --Yes local timer_at = ngx.timer.at local function foo() local ok, err = timer_at(delay, handler) end ``` For style unification, `require` and `ngx` also need to be localized: ```lua --No local core = require("apisix.core") local timer_at = ngx.timer.at local function foo() local ok, err = timer_at(delay, handler) end ``` ```lua --Yes local ngx = ngx local require = require local core = require("apisix.core") local timer_at = ngx.timer.at local function foo() local ok, err = timer_at(delay, handler) end ``` For functions that return with error information, the error information must be judged and processed: ```lua --No local sock = ngx.socket.tcp() local ok = sock:connect("www.google.com", 80) ngx.say("successfully connected to google!") ``` ```lua --Yes local sock = ngx.socket.tcp() local ok, err = sock:connect("www.google.com", 80) if not ok then ngx.say("failed to connect to google: ", err) return end ngx.say("successfully connected to google!") ``` The function you wrote yourself, the error message is to be returned as a second parameter in the form of a string: ```lua --No local function foo() local ok, err = func() if not ok then return false end return true end ``` ```lua --No local function foo() local ok, err = func() if not ok then return false, {msg = err} end return true end ``` ```lua --Yes local function foo() local ok, err = func() if not ok then return false, "failed to call func(): " .. err end return true end ```