Re: from: Lua Module Function Critiqued
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- Subject: Re: from: Lua Module Function Critiqued
- From: steve donovan <steve.j.donovan@...>
- Date: Wed, 9 Oct 2013 08:50:02 +0200
On Wed, Oct 9, 2013 at 3:02 AM, Tom N Harris <telliamed@whoopdedo.org> wrote:
> The module function is mutating the first upvalue of the calling function
> without regard to whether it is the _ENV table.
The 5.2 compat module is indeed too simplistic - I found this out when
trying to pack multiple modules into a single Lua file.
Building module() on this would work properly, subject to Roberto's
caveat - note that it isn't a cheap operation!
-- setfenv/getfenv replacements for Lua 5.2
-- by Sergey Rozhenko
-- http://lua-users.org/lists/lua-l/2010-06/msg00313.html
-- Roberto Ierusalimschy notes that it is possible for getfenv to return nil
-- in the case of a function with no globals:
-- http://lua-users.org/lists/lua-l/2010-06/msg00315.html
function compat.setfenv(f, t)
f = (type(f) == 'function' and f or debug.getinfo(f + 1, 'f').func)
local name
local up = 0
repeat
up = up + 1
name = debug.getupvalue(f, up)
until name == '_ENV' or name == nil
if name then
debug.upvaluejoin(f, up, function() return name end, 1) --
use unique upvalue
debug.setupvalue(f, up, t)
end
if f ~= 0 then return f end
end
function compat.getfenv(f)
local f = f or 0
f = (type(f) == 'function' and f or debug.getinfo(f + 1, 'f').func)
local name, val
local up = 0
repeat
up = up + 1
name, val = debug.getupvalue(f, up)
until name == '_ENV' or name == nil
return val
end
end
(This is from Penlight's pl.compat module; these guys are exported by
pl.utils as utils.(get|set)fenv)
It's an academic point personally, because I've been a happy non-user
of module() for years. But I will say that converting codebases that
use module() is an error-prone process unless you use a static
analysizer