[gentoo-user] Advice appreciated regarding how to handle Perl modules correctly in an ebuild

[Morgan Wesström]

Dear list,

I'm trying to create an ebuild for a ZFS snapshot/replication automation tool
called Znapzend that I've been using on FreeBSD for some time and also would
like to use in Gentoo. https://github.com/oetiker/znapzend

The project homepage has a link to a 3 year old abandoned ebuild that no longer
works. The program exists as a package in FreeBSD and also in Arch Linux and
I've used all these sources to try to understand the best approach how to
handle it in Gentoo.

I've managed to create a working ebuild but I need some input for the final
install phase. The program is written in Perl and creates a few modules. The
above mentioned sources do not agree on the location of these files and gives
no hints to why the maintainers chose the solution they did.

The FreeBSD approach seems straight forward and places the files accordingly:
/usr/local/lib/perl5/site_perl/ZnapZend.pm
/usr/local/lib/perl5/site_perl/ZnapZend/Config.pm
/usr/local/lib/perl5/site_perl/ZnapZend/Time.pm
/usr/local/lib/perl5/site_perl/ZnapZend/ZFS.pm
/usr/local/lib/perl5/site_perl/inheritLevels.pm

In Gentoo I find .pm files in a multitude of places e.g.
/usr/lib64/perl5/5.36
/usr/lib64/perl5/vendor_perl/5.36

This is where I lack the necessary knowledge to proceed.

1) Where's the appropriate place for these files in Gentoo and why?

2) If the appropriate place is either of those folders with a version number,
how do I install the files there without hard coding the version number in the
ebuild (which would naturally break the next time Perl gets updated)?

Regards
Morgan Wesström

[Jack]

Post by Morgan Wesström
Dear list,
I'm trying to create an ebuild for a ZFS snapshot/replication
automation tool called Znapzend that I've been using on FreeBSD for
some time and also would like to use in Gentoo.
https://github.com/oetiker/znapzend
The project homepage has a link to a 3 year old abandoned ebuild that
no longer works. The program exists as a package in FreeBSD and also
in Arch Linux and I've used all these sources to try to understand
the best approach how to handle it in Gentoo.
I've managed to create a working ebuild but I need some input for the
final install phase. The program is written in Perl and creates a few
modules. The above mentioned sources do not agree on the location of
these files and gives no hints to why the maintainers chose the
solution they did.
/usr/local/lib/perl5/site_perl/ZnapZend.pm
/usr/local/lib/perl5/site_perl/ZnapZend/Config.pm
/usr/local/lib/perl5/site_perl/ZnapZend/Time.pm
/usr/local/lib/perl5/site_perl/ZnapZend/ZFS.pm
/usr/local/lib/perl5/site_perl/inheritLevels.pm
In Gentoo I find .pm files in a multitude of places e.g.
/usr/lib64/perl5/5.36
/usr/lib64/perl5/vendor_perl/5.36
This is where I lack the necessary knowledge to proceed.
1) Where's the appropriate place for these files in Gentoo and why?
2) If the appropriate place is either of those folders with a version
number, how do I install the files there without hard coding the
version number in the ebuild (which would naturally break the next
time Perl gets updated)?
Regards
Morgan Wesström

I'd suggest looking at ebuilds created by g-cpan, which produces
ebuilds for any module in CPAN. I suspect the eclass(es) involved deal
with the perl version issue. I don't think you can savely ignore that,
since there are likely to be things in the module which do depend on
the version of perl used to create that module.

[Morgan Wesström]

Post by Morgan Wesström
1) Where's the appropriate place for these files in Gentoo and why?
2) If the appropriate place is either of those folders with a version number,
how do I install the files there without hard coding the version number in
the ebuild (which would naturally break the next time Perl gets updated)?
Regards
Morgan Wesström

I'd suggest looking at ebuilds created by g-cpan, which produces ebuilds for
any module in CPAN.  I suspect the eclass(es) involved deal with the perl
version issue.  I don't think you can savely ignore that, since there are
likely to be things in the module which do depend on the version of perl used
to create that module.

Thank you, Jack. Digging through some ebuilds in the dev-perl category was the
first thing I did. It led me to the perl-module eclass but I can only find
reference documentation which doesn't tell me how to use it or how its
functions hook into the build system. I lack fundamental knowledge of how Perl
is organized and I'm an old guy which mean I have to be selective with new
knowledge not t be overwhelmed. ;) How DO I know if either module is dependent
on a specific Perl version for example?

In the old ebuild I found online, the developer just creates a
/usr/share/znapzend/perl5 folder and puts all those files there.

https://git.gerczei.eu/tgerczei/gentoo-overlay/src/branch/master/app-backup/znapzend/znapzend-0.20.0.ebuild

I could easily do that and be done with it but this is also an opportunity to
absorb some new knowledge and to know that I made the correct choice and why
this choice is the correct one in this situation.

Regards
Morgan

[Jack]

Post by Morgan Wesström

Post by Jack

Post by Morgan Wesström
1) Where's the appropriate place for these files in Gentoo and why?
2) If the appropriate place is either of those folders with a
version number, how do I install the files there without hard
coding the version number in the ebuild (which would naturally
break the next time Perl gets updated)?
Regards
Morgan Wesström

I'd suggest looking at ebuilds created by g-cpan, which produces
ebuilds for any module in CPAN.  I suspect the eclass(es) involved
deal with the perl version issue.  I don't think you can savely
ignore that, since there are likely to be things in the module which
do depend on the version of perl used to create that module.

Thank you, Jack. Digging through some ebuilds in the dev-perl
category was the first thing I did. It led me to the perl-module
eclass but I can only find reference documentation which doesn't tell
me how to use it or how its functions hook into the build system.

I don't know if it's actually useful, but note I suggested perl-gcpan
not dev-perl. I don't know how different those generated ebuilds are
from ones in dev-perl, but they are created "on the fly" from the CPAN
entry for the module. You could try it on some CPAN module you think
has some similarities to one of the znapzend perl modules. I don't
know how to know if a perl module truly depends on the perl version,
but I don't think it hurts to make that assumption. The only cost I
see is a possibly unnecessary rebuild on a perl upgrade.

Post by Morgan Wesström
I lack fundamental knowledge of how Perl is organized and I'm an old
guy which mean I have to be selective with new knowledge not t be
overwhelmed. ;) How DO I know if either module is dependent on a
specific Perl version for example?

I might challenge you on age, and the mere fact that you are using
Gentoo, and messing with ebuilds puts you far ahead of the general
crowd. I'm currently trying to make an application work with Qt6, so
don't underestimate what you can figure out how to do.

Post by Morgan Wesström
In the old ebuild I found online, the developer just creates a
/usr/share/znapzend/perl5 folder and puts all those files there.
https://git.gerczei.eu/tgerczei/gentoo-overlay/src/branch/master/app-backup/znapzend/znapzend-0.20.0.ebuild
I could easily do that and be done with it but this is also an
opportunity to absorb some new knowledge and to know that I made the
correct choice and why this choice is the correct one in this
situation.

The znapaend readme says something about any necessary perl modules
being installed within the znapzend area and not within the system
perl, so that might actually be a reasonable place to also put their
own perl modules. You could also dig into the package for one of the
other distributions and see where they put the various pieces.

Post by Morgan Wesström
Regards
Morgan

Jack

[William Kenworthy]

Post by Morgan Wesström

Post by Jack

Post by Morgan Wesström
1) Where's the appropriate place for these files in Gentoo and why?
2) If the appropriate place is either of those folders with a
version number, how do I install the files there without hard coding
the version number in the ebuild (which would naturally break the
next time Perl gets updated)?
Regards
Morgan Wesström

I'd suggest looking at ebuilds created by g-cpan, which produces
ebuilds for any module in CPAN.  I suspect the eclass(es) involved
deal with the perl version issue.  I don't think you can savely
ignore that, since there are likely to be things in the module which
do depend on the version of perl used to create that module.

Thank you, Jack. Digging through some ebuilds in the dev-perl category
was the first thing I did. It led me to the perl-module eclass but I
can only find reference documentation which doesn't tell me how to use
it or how its functions hook into the build system. I lack fundamental
knowledge of how Perl is organized and I'm an old guy which mean I
have to be selective with new knowledge not t be overwhelmed. ;) How
DO I know if either module is dependent on a specific Perl version for
example?
In the old ebuild I found online, the developer just creates a
/usr/share/znapzend/perl5 folder and puts all those files there.
https://git.gerczei.eu/tgerczei/gentoo-overlay/src/branch/master/app-backup/znapzend/znapzend-0.20.0.ebuild
I could easily do that and be done with it but this is also an
opportunity to absorb some new knowledge and to know that I made the
correct choice and why this choice is the correct one in this situation.
Regards
Morgan

Also, are you aware of perl-cleaner? - it takes care of perl packages
after an upgrade.

This is a good read: https://wiki.gentoo.org/wiki/Perl

BillK

[Morgan Wesström]

I'd suggest looking at ebuilds created by g-cpan, which produces ebuilds for
any module in CPAN.

I was looking at this early on but didn't think I would need it but it turned
out that there was one more dependency I had missed. g-cpan worked very well,
integrated itself automatically with Portage and put the generated ebuild in my
localrepo. For now I just add g-cpan as a dependency to my ebuild with an elog
message at the end with instructions how to install the missing module. I'll be
looking for a way to trigger that automatically after the main program is emerged.

Regarding the location for the Perl modules created by znapzend, I ended up
putting them in a separate folder for now until I can find some best practices
on how to handle them. The ebuild works and I'm running tests on znapzend at
the moment to see that I didn't miss more dependencies.

Thank you for your input and if anyone has info on best practices regarding
Perl modules location and how to make your ebuild automatically put them in the
current versioned vendor_perl folder, I'm all ears.

Morgan