require function for loading Lua modules

Sun, 17 Mar 2024 11:21:24 UTC

I wrote Lua require function based on the include function found in /system/lib/head.lua:791.

This function loads Lua modules similar to standard require found in Lua:

it loads the file
executes the file
returns the module returned by included file
caches the module, so next call to require will return already loaded module

How to use:

put the source code of require function in your main.lua:

function require(name)
   if _modules == nil then
        _modules={}
    end

    local already_imported = _modules[name]
    if already_imported ~= nil then
        return already_imported
    end

    local filename = fullpath(name..'.lua')
    local src = fetch(filename) 

    if (type(src) ~= "string") then 
        notify("could not include "..filename)
        stop()
        return
    end 

    -- https://www.lua.org/manual/5.4/manual.html#pdf-load
    -- chunk name (for error reporting), mode ("t" for text only -- no binary chunk loading), _ENV upvalue
    -- @ is a special character that tells debugger the string is a filename
    local func,err = load(src, "@"..filename, "t", _ENV)
    -- syntax error while loading
    if (not func) then 
        send_message(3, {event="report_error", content = "*syntax error"})
        send_message(3, {event="report_error", content = tostr(err)})

        stop()
        return
    end

    local module = func()
    _modules[name]=module

    return module
end

write modules, for example create file named module.lua:

M = {}

function M.func()
    print("inside module.func()")
end

return M

import modules:

local module = require('module') -- will load and execute module.lua
module.func()

elgopher [Lexaloffle Blog Feed]

require function for loading Lua modules