Lua environments when calling function within setfenv function

Question

So I have a Lua script in which I set the environment of a function and define other functions that I make available in the environment. The issue is that when I call the function I did setfenv on, any function it calls within the environment uses the global _G environment to lookup values as opposed to the environment I set when calling the initial function. I have replicated the issue below:

> function f() print(t) end
> t = 5
> f()
5
> env = {}
> env['print'] = print
> env['t'] = 7
> env['f'] = f
> setfenv(f, env)
> f()
7
> setfenv(f, _G)
> f()
5
> function g() f() end
> g()
5
> setfenv(g, env)
> g()
5

Is there a way to get the environment to propagate to all calls without having to do setfenv on every function I want to add to env (basically, so that the last call in the example to g() would return 7 instead of 5)?

Using Lua 5.1.

• Egor Skriptunoff: Function environments in Lua 5.1 are not inherited by function invocation (you have to manually call setfenv before calling that function to solve your problem). New environment system (since 5.2, using _ENV) makes correct inheritance easily possible.
• Ford: Is there no way to replicate this behaviour in 5.1?

Answer 1

You can write a function so that it automatically changes its own environment on every call

-- This code works on Lua 5.1, 5.2, 5.3
local getfenv = getfenv or function() end
local setfenv = setfenv or getfenv
a = 1
function f(env)
 local _ENV = env or getfenv(2) or _ENV; setfenv(1, _ENV)
 print(a)
end
env = { a = 2, print = print }
-- inherit environment for this call
f() --> 1
-- set special environment for this call
f(env) --> 2
f() --> 1

Or simply setfenv(1, getfenv(2)) if you are working only with Lua 5.1 and want to ALWAYS inherit environment.