Re: Relative Requires in Lua

[Philipp Janda <siffiejoe@...>]

Am 13.10.2016 um 21:28 schröbte Soni L.:
> For two, Lua's module system fully supports relative requires. This is
> one of the most overlooked features of Lua! I see people doing `local
> submod = require "thismod.submod"` all the time. That's not how you do it!
>
> The proper way to do relative requires is:
>
> thismod/init.lua
> -----
> local modname = ...
> local submod = require(modname .. ".submod")
> return {submod=submod}
> -----
>
> thismod/submod.lua
> -----
> return {
>   helloworld = function() print("Hello World!") end
> }
> -----
>
> Then, if you require "thismod", you can call
> thismod.submod.helloworld(). However, if you rename the thismod
> directory, and require the new directory name, it'll still work! Unlike
> when using hardcoded module names.

I think relative `require` is an anti-pattern for the following reasons:

1.  The module name is part of the public interface, so you shouldn't 
rename it at all (or at least bump the major version number afterwards).

2.  If you move a module `a.x` to `a.s.x`, all relative `require`s in 
this module *and of* this module break. With absolute `require` only the 
`require`s *of* this module need to be fixed.

3.  It only works for internal modules that are never `require`d from 
the outside or else the renaming feature stops working anyway.

4.  It leads to bloat. For modules like

        return { -- file a.lua
          b = require( ... .. ".b" ),
          c = require( ... .. ".c" ),
          -- ...
        }

    `local a = require("a")` will load all submodules even if only a 
few of those modules are actually needed.

5.  The interface gets uglier as well:

        local a = require( "a" )
        a.b.u.x.func()

    compared to

        local x = require( "a.b.u.x" )
        x.func()

6.   You can run into `require` cycles if module `a.b.u.x` needs 
functions from module `a.b` but should also be part of it.

Philipp