Date: Thu, 27 Jun 2013 15:34:58 +0200
From: Natanael Copa <ncopa@alpinelinux.org>
To: Dubiousjim <lists+alpine-devel@jimpryor.net>
Cc: alpine-devel@lists.alpinelinux.org
Subject: Re: [alpine-devel] upgrading to Lua 5.2
Message-ID: <20130627153458.6cb088c8@ncopa-desktop.alpinelinux.org>
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On Wed, 26 Jun 2013 17:38:11 -0400
Dubiousjim <lists+alpine-devel@jimpryor.net> wrote:

> On Wed, Jun 19, 2013 at 04:01:41PM +0200, Natanael Copa wrote:
> 
> > I have been looking at upgrading to Lua 5.2. Many things is just a
> > question of recompile and some needs porting...
> 
> Hi Natanael, I'll definitely help with porting things to Lua 5.2, though
> it may be a few weeks before I can get into it.
> 
> > Those failed and still need some work:
> > 
> > vlc
> > squark
> > rrdtool
> > lighttpd
> > kamailio
> > tolua++
> > conky
> > cegui06
> > 
> > Some of them looks non-trivial, like squark.
> > 
> > I asked in #lighttpd and there was some resistance from upstream to
> > port the stable lighttpd to lua 5.2 as it risks to break users scripts.
> 
> That's too bad. Not surprising that some upstreams are going to have
> that position, though. I doubt they'll be the only ones.

I figured. So it means that the only sane way forward is to support both 5.1 and 5.2 in parallel.

> Maybe I can port lighttpd's buildsystem to honor a --with-luafiveq flag,
> and if built in that way, to work with either Lua 5.1 or Lua 5.2 on the
> host system, and load user scripts in such a way as to be maximally
> compatible with both. Then we can try to persuade the upstream guys to
> test that, and if they like it, to roll it in. It'd be a good test case
> for luafiveq. I use lighttpd anyway (but not atm any lua scripts for
> it). I'll put this on my mental queue of things to do when I can.

I think we could just port it to 5.2, and maintain a patch. The patch
could be posted in lighttpd's bugtracker/wiki so others could test it
too.

> > Now, I am still a bit in doubt how we move forward. I think we have the
> > following options:
> > 
> > One shot upgrade
> > One shot upgrade, with partial 5.1 compatibility
> > Append 5.2 and migrate slowly over
> > Support both versions in parallel
 
> I'd incline towards one of the middle options also. Perhaps a backend
> where there are lua51-foo and lua52-foo packages (installing to
> /usr/{lib,share}/lua5{1,2} directories), and a lua-foo metapackage that
> just depends on one of those. That makes for more manual work for those
> working on the packaging, but I don't think it'll be too bad.
>
> Like Arch did when they made Python 3.x their default python, we can
> just make sure that any apk-installed lua scripts use:
>     #!/usr/bin/lua51
> instead of:
>     #!/usr/bin/lua
> .

This is what i originally wanted but i realized that it would break
things for users. (python broke things for arch users too)
 
> Then we might push option 3 first, and once that's working cleanly we
> can step back and assess when is the right time to shift all the lua-foo packages to
> depend on lua52-foo instead of lua51-foo. Actually implementing that
> change will then be trivial. But we'd have gotten some broad testing in
> beforehand, from users who try out lua52-foo directly.
> 
> > Drawbacks:
> >   ...
> >   We get same problem when 5.3 comes out.
> 
> I wouldn't worry about that. Have a look at
> <http://www.lua.org/versions.html>. Should be many years.

Thats what I thought when i built first Lua (5.1) packages :)
 
> As you also observed, it'd be a lot of packages. This is a downside, but
> seems a minor one to me.
> 
> 
> Here are some more detailed suggestions:
> 
> One git commit (or set of commits): all folders lua-foo in aports moved to lua51-foo, and
> all references to lua-foo in any APKBUILD also so modified; at the same
> time, lua51-foo gets a release bump. Same with the base "lua" package.
>
> (It looks from some recent aports commits like you're starting to do
> something along these lines. I haven't looked closely yet, though.)
> 
> Second git commit(s): add new folders lua-foo, with APKBUILD having same
> version/release as lua51-foo, and simply depending on lua51-foo. The
> idea is that no package will refer to lua-foo, this is just for "apk add
> lua-foo". Same with the base "lua" package.
> 
> Those two (sets of) commits could then be pushed out.
> 
> Third commit(s): /usr/{share,lib}/lua moved to /usr/{share,lib}/lua51, all
> affected APKBUILDs and Makefiles adjusted to suit; all those packages
> get a release bump.
> 
> Fourth commit(s): Make base "lua51" package install binaries at
> /usr/bin/lua51, and symlink to that with /usr/bin/lua; also gets a
> release bump. Also, any package that installs a #!/usr/bin/lua script has
> that changed to say #!/usr/bin/lua51, and gets a release bump.

I dropped those 4 commits for now and just added lua5.1 (and
lua5.1-dev). I added a symlink package named 'lua' that for now only
pulls in lua5.1 and creates symlinks /usr/lib/pkgconfig/lua.pc ->
lua5.1.pc and /usr/bin/lua -> lua5.1

This was so that nothing existing breaks. Once we have ported most
stuff to lua5.2 we could point the lua symlinks to the 5.2.

> Fifth commit: add lua52 package.

I added a package named lua5.2 instead of lua52. I must admit i liked
lua52 better but we have similar names for libcrypto1.0, goffice0.8 etc
so we better try stay consequent.

> 
> Sixth commit(s): start copying lua51-foo packages to lua52-foo, and
> building/installing for lua52.

This is where I am now. I am copying lua-foo to lua5.2-foo in testing.
 
> Down the road:
> * Application packages that depend on lua, like lighttpd,
> might be rebuilt with lua52, and change their dependencies accordingly.

Yes. I think the packages I managed to rebuild against 5.2 so far
should be fairly easy.

> * lua51 no longer installs the symlink /usr/bin/lua, instead lua52 does
> this (or neither does it, user does it him/herself).

What we will do is just update the 'lua' package that currently depends
on lua5.1 and has symlinks pointing to lua5.1 files to depend on lua5.2
and point the symlinks accordingly.

At this point we should probably rebuild the stuff that depends on
'lua' (5.1) so the depend on 'lua5.1' instead.

> * lua-foo packages start depending on lua52-foo instead of lua51-foo.
> 
> Way down the road:
> * lua51 and all the lua51-foos get dropped. I'd just leave the
> lua-foo/lua52-foo infrastructure in place, though. A bunch of extra
> folders in the package tree don't hurt much. Main downside is that
> whenever you version-bump one of them, you'd have to remember to bump
> both.

I think we will have to maintain both for a while :-/ unless ACF devs
start porting to lua 5.2.

Thanks for your feedback!

-nc


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