Re: [Caml-list] [OSR] Ports-like package management system

["Nicolas Pouillard" <nicolas.pouillard@gmail.com>]

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Excerpts from Yaron Minsky's message of Tue Jan 29 14:47:03 +0100 2008:
> Another thought: the discussion here is essentially about cloning  
> haskell's cabal system. Seems like a good place to look for inspiration.

I  also  think  that  many  ideas  can be borrowed from cabal since it's quite
recent and have close requirements.

> 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.

-- 
Nicolas Pouillard aka Ertai

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