user defined loader

mymod.user.lua

local M = {}

function M.test(...)
	print(...)
end

return M

requirenv.lua

local package = package
local debug = debug

local function load_env(filename)
	local f,err = loadfile(filename)
	if f == nil then
		return err
	end
	return function()
		return function(env)
			if env then
				debug.setupvalue(f, 1, env)
			end
			return f(filename)
		end
	end
end

local function searcher_env(name)
	local filename, err = package.searchpath(name, package.upath)
	if filename == nil then
		return err
	else
		return load_env(filename)
	end
end

table.insert(package.searchers, searcher_env)

test.lua

require "requirenv"

package.upath = "./?.user.lua"

local myprint = print

local env = {
	print = function (...)
		myprint("hook", ...)
	end
}

local s = require "mymod"(env)

s.test "hello world"  -- hook hello world