[DCPM] hierarchies

[Simon Waters]

Neil Williams wrote:
> 
> Given an existing set of packages A, which packages need to be built
> *FIRST* in order to eventually build a system to support package set B.

Can you define what problem you are trying to solve, rather than what
you think you need to do to solve it.

> Any ideas? (or should I do this in C?)

Perl surely ;)

> Is something similar already available?

CPAN already does some of this.

The guy who wrote some of the CPAN tools, also produced tools for
creating Debian packages from CPAN, the archives of the Debian Perl
group discuss a lot of the issues of packaging Perl modules for Debian,
and as a side effect some work was done on dependencies. There are at
least two major sets of tools for doing the CPAN -> Deb transition....

As regards external dependencies, I don't think CPAN, or the modules,
contain enough explicit information to say what is needed to reliably
build a module that requires to compile C code. Although I dare say a
lot of cases can be automated.

Similarly some the CPAN dependencies are optional, and CPAN (or a
descendant) will prompt which way you want to do something. So CPAN
dependencies can get pretty complex.

There are some tools to build Perl executables, which will pull all the
Perl modules to achieve some task. But then Perl being Perl there are
also on demand tools, that get those modules when they are needed. Dare
I say there is more than one way to do it!

A scary amount of new Perl modules appear in Etch. We are doing Catalyst
work at ZyNet, and these days "apt-get install libcatalyst-perl" gets
you a working system. Although I wouldn't like to comment how up to date
it is, we have too much CPAN stuff, and I don't think we have the
version management as strict as we should.

But then most of our Perl code before the Catalyst app had only shallow
dependencies, probably a tie to a Postgres database is the deepest we've
gone previously. Indeed quite a lot of our Perl code pre-empted what is
now in CPAN, as it was written be people who long predated me, at least
one of whom was both brighter and better educated that I.

So module version management is likely to become a big issue for me as
system administrator. Especially with tools like "Version", which make
the task potentially harder (well harder for the system admin, if easier
for the programmer).



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