How can I write a library which has multiple files using require?

[jorolf]

I'm currently working on a library which has multiple files that depend on each other. (not cyclically)

Imagine:

/lib
|---foo.lua
\---bar.lua

How can I consistently load bar.lua inside foo.lua? Using require means that I depend on package.path which is set depending on the main lua file:

main1.lua
lib/
|---examples/
    \---main3.lua
|---foo.lua
|---bar.lua
\---main2.lua

For main1.lua I would have to require lib.bar
For main2.lua I would have to require just bar
And for main3.lua it's impossible because ../bar doesn't work

Note that I don't mean main -require-> bar but foo -require-> bar

[SquidDev]

I'd set package.path inside your entrypoints, so that lib is always on the path. This way both your entrypoints and other libraries only need to do require "foo"/require "bar".

So, in the case of main1.lua, something like

package.path = "lib/?.lua:" .. package.path 

local foo = require "foo"

[jorolf]

This is probably the simplest solution. However I don't like how it puts the burdon on the library user and not the implementor.... Do you know if there's another way?

[SquidDev]

It only really puts the burden on the library user if they want to do something different with folder layout - if things are in the same directory, the user doesn't have to anything extra.

There's something nasty one could do with module names, but I don't think it's the right solution - I'll write it up as a separate answer.

[jorolf]

Thanks for the suggestions. I've settled for the simpler variant. Your example contains an error though: It should be "lib/?.lua;" instead of "lib/?.lua:"

It only really puts the burden on the library user if they want to do something different with folder layout

I like to organize my files into modules or packages instead of just placing them all in the same directory/file

[SquidDev]

The current module name (foo, lib.foo) gets passed to the required module, so you could use that to implement a sort-of-relative import. It's not very nice though:

local function get_prefix(str)
  local pos
  while true do
    local next = str:find(".", pos, true)
    if not next then break end
    pos = next + 1
  end

  if pos then return str:sub(1, pos - 1) else return "" end
end
local prefix = get_prefix(...) -- Will be something like "lib." or "".

local bar = require(prefix .. "bar") -- So will be "lib.bar" or "bar"