Deprecating setfenv()

[Peter Odding <peter@...>]

Hi everyone,

From what I've seen so far I like most of the changes in Lua 5.2.0 but 
there's one thing I cannot wrap my mind around. It looks like getfenv() 
and setfenv() are being moved to the debug library (in other words 
deprecated) while the supposed replacement really isn't...

Several of the modules I've written use setfenv() and though each of 
those modules contains just a single call to setfenv() the functionality 
of the whole module depends on that setfenv() call. Apart from that, if 
my understanding is correct then the supposed replacement is really just 
a simple syntactical wrapper for the following functionality:

local scope = {}
setfenv(function()
	foo = 1
	bar = 2
end, scope)()
assert(foo == nil)
assert(bar == nil)
assert(scope.foo == 1)
assert(scope.bar == 2)

This is obviously already possible in Lua 5.1, but more importantly it 
is one very narrow use-case of setfenv(). I've grown to appreciate 
setfenv() as core Lua functionality and now it is being deprecated 
without a replacement...

Finally I'm getting to my point: I'm wondering what made the Lua authors 
decide to remove setfenv() and replace it with a very narrow subset of 
its functionality?! Of course I'm hoping that I misunderstood the 
replacement or can change the Lua authors' minds about it, but if 
neither of those is an option than I'll settle for a clear understanding 
of the decision making process :-)

 - Peter Odding