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Date: -- (:)
From: Yaron Minsky <yminsky@g...>
Subject: Re: [Caml-list] [OSR] Ports-like package management system
Another thought: the discussion here is essentially about cloning  
haskell's cabal system. Seems like a good place to look for inspiration.

Yaron Minsky

On Jan 29, 2008, at 5:56 AM, Berke Durak <berke.durak@exalead.com>  
wrote:

> Hello,
>
> Following Markus's message, discussions with Nicolas Pouillard and
> Sylvain Le Gall and others, and of course my previous work in the EDOS
> project, here are some thoughts about package management systems
> (PMSs) for Ocaml.
>
> First, the PMSs of Linux distributions are perfectly adequate for end
> users and administrators having to deploy and manage identical
> packages accross multiple machines.  These are very complex systems
> including a substantial social part.
>
> But they are not very suitable for developers.
>
> As Markus pointed out, developers cannot go thru a packaging step to
> test the result of a change, much less wait for the fine Debian team.
>
> One reason is that most developers, including myself, cannot be
> bothered to package software for a Linux distribution, because correct
> packaging is complex and requires adherence to a set of rules must be
> remembered and which cannot all be checked by software.  As packaging
> is not done very often, you tend to forget those rules, and that is
> why we have people who package often to not forget the rules:
> maintainers.  Without maintainers, we would be in a world of pain to
> install any piece of non-trivial software and we are thankful to them.
>
> But developers absolutely need to be able to work on multiple versions
> of the same software component at once, patch those versions or
> compile them with unusual flags, and often use the absolutely latest
> unpackaged version.  And that is the second reason why the Debian or
> Red Hat PMSs are not adequate.  They have a single global state per
> system, which includes the installed files, and the package database,
> and cannot handle multiple versions of the same package, nor multiple
> compilations of the same version.  (This also applies to Gentoo.)
>
> We thus need versions, and lots of them!  We need to base our
> developer packages on a version control system, in the style of BSD
> ports.  BSD ports are usually based on CVS, sometimes on Subversion.
> As we are looking to increase collaboration, having a single point of
> contention is a serious limitations of these centralized systems;
> we'll prefer more recent "distributed" version control system.
>
> Of available distributed VCSs with a serious user base, we have Darcs,
> Mercurial and Git.
>
> Basing a PMS for Ocaml on a VCS written in Haskell would violate the
> ``Trading with the Enemy'' act.  Moreover Darcs has some performance
> problems of its own.
>
> Mercurial (Hg) is written in Python extended in C for performance.  It
> is quite friendly and works well under Windows.  However, its
> developers are not as elite as Git's, its merging features are less
> advanced and Python sux0rz.
>
> I have been using Hg for the past few months and been quite happy with
> it, but then I was mostly working alone.  Git is certainly as good as
> Mercurial for that kind of usage and, as it is written in pure C, I
> advocate its use.  Until someone writes a VCS in Ocaml, that is.
>
> Let's get back to the subject.  BSD ports are also based on make,
> whose main limitation, the static dependency graph, has been addressed
> in ocamlbuild.  I know there is Omake, but I think it suffers from the
> ``Yet Another Turing-Complete Language'' syndrome.
>
> So I am calling for a solution based on a ports-like system but based
> on a distributed VCS and on an improved ocamlbuild.
>
> Assume you are writing a program FOO and want to use a package BAR
> available from bar.org.  You tell ocamlbuild by adding some tag such
> as
>
>  <mytarget.native>: require(http://bar.org/repository/)
>
> And when you run ocamlbuild, it automatically checks out a copy of
> BAR, compiles and loads its myocamlbuild.ml module which adds the
> required flags.  Of course it should be possible to specify a
> particular revision...  And if BAR has itself dependencies, those too
> would be checked out.
>
> Note that Git has a nice option for cloning checked out repositories
> using hard links; that could be used to maintain a cache of checkouts,
> for instance in the user's ~/.ocamlbuild/checkouts/ directory.
>
> So basically I propose that we improve ocamlbuild to allow for
> multiple plugin files (using dynamic loading) and use that to define a
> BSD ports-like system targeted at developers.
>
> -- 
> Berke DURAK
>
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