ltn12 should not export global table

[johnd0e]

luasocket/src/ltn12.lua

Lines 16 to 19 in 1fad162

	local _M = {}
	if module then -- heuristic for exporting a global package table
	ltn12 = _M -- luacheck: ignore
	end

module function exists in 5.1 (in 5.2 manual it is referenced as deprecated).
Still nobody nowadays expect that module exports globals.
Nor other (sub)modules of luasocket do that.

[alerque]

I agree this should be removed, but doing so will probably warrant a breaking release semver bump because it will not be a smooth upgrade path for anybody that was relying on this quirk.

[johnd0e]

I tend to view that as fixing a bug, which only requires a minor version bump. Of course, there may be someone who relies on the bug in their own workflow, but it is still a bug.

[catwell]

A long time ago almost all Lua modules used to export a global. ltn12 is a module from that era and used in a lot of places. So yes I can guarantee you changing this will break code, it should be done in a major revision.