# PODNAME: Alien::Build::Manual::Contributing
# ABSTRACT: Over-detailed contributing guide
# VERSION

__END__

=pod

=encoding UTF-8

=head1 NAME

Alien::Build::Manual::Contributing - Over-detailed contributing guide

=head1 VERSION

version 2.41

=head1 SYNOPSIS

 perldoc Alien::Build::Manual::Contributing

=head1 DESCRIPTION

Thank you for considering to contribute to my open source project!  If
you have a small patch please consider just submitting it.  Doing so
through the project GitHub is probably the best way:

L<https://github.com/plicease/Alien-Build/issues>

If you have a more invasive enhancement or bugfix to contribute, please
take the time to review these guidelines.  In general it is good idea to
work closely with the L<Alien::Build> developers, and the best way to
contact them is on the C<#native> IRC channel on irc.perl.org.

=head2 History

Joel Berger wrote the original L<Alien::Base>.  This distribution
included the runtime code L<Alien::Base> and an installer class
L<Alien::Base::ModuleBuild>.  The significant thing about L<Alien::Base>
was that it provided tools to make it relatively easy for people to roll
their own L<Alien> distributions.  Over time, the PerlAlien (github
organization) or "Alien::Base team" has taken over development of
L<Alien::Base> with myself (Graham Ollis) being responsible for
integration and releases.  Joel Berger is still involved in the project.

Since the original development of L<Alien::Base>, L<Module::Build>, on
which L<Alien::Base::ModuleBuild> is based, has been removed from the
core of Perl.  It seemed worthwhile to write a replacement installer
that works with L<ExtUtils::MakeMaker> which IS still bundled with the
Perl core.  Because this is a significant undertaking it is my intention
to integrate the many lessons learned by Joel Berger, myself and the
"Alien::Base team" as possible.  If the interface seems good then it is
because I've stolen the ideas from some pretty good places.

=head2 Philosophy

=head3 Alien runtime should be as config-only as possible.

Ideally the code for an L<Alien::Base> based L<Alien> should simply
inherit from L<Alien::Base>, like so:

 package Alien::libfoo;
 
 use parent qw( Alien::Base );
 
 1;

The detection logic should be done by the installer code (L<alienfile>
and L<Alien::Build>) and saved into runtime properties (see
L<Alien::Build/runtime_prop>).  And as much as
possible the runtime should be implemented in the base class (L<Alien::Base>).
Where reasonable, the base class should be expanded to meet the needs
of this arrangement.

=head3 when downloading a package grab the latest version

If the maintainer of an L<Alien> disappears for a while, and if the
version downloaded during a "share" install is hardcoded in the
L<alienfile>, it can be problematic for end-users.

There are exceptions, of course, in particular when a package provides
a very unstable interface from version to version it makes sense
to hard code the version and for the Alien developer and Alien consumer
developer to coordinate closely.

=head3 when installing a package the operating system as a whole should not be affected

The convenience of using an L<Alien> is that a user of a CPAN module
that consumes an L<Alien> doesn't need to know the exact incantation
to install the libraries on which it depends (or indeed it may not be
easily installed through the package manager anyway).

As a corollary, a user of a CPAN module that consumes an L<Alien>
module shouldn't expect operating system level packages to be
installed, or for these packages to be installed in common system
level directories, like C</usr/local> or C</opt>.  Instead a "share"
directory associated with the Perl install and L<Alien> module
should be used.

Plugins that require user opt-in could be written to prompt a user
to automatically install operating system packages, but this should
never be done by default or without consent by the user.

=head3 avoid dependencies

One of the challenges with L<Alien> development is that you are by the
nature of the problem, trying to make everyone happy.  Developers
working out of CPAN just want stuff to work, and some build environments
can be hostile in terms of tool availability, so for reliability you end
up pulling a lot of dependencies.  On the other hand, operating system
vendors who are building Perl modules usually want to use the system
version of a library so that they do not have to patch libraries in
multiple places.  Such vendors have to package any extra dependencies
and having to do so for packages that the don't even use makes them
understandably unhappy.

As general policy the L<Alien::Build> core should have as few
dependencies as possible, and should only pull extra dependencies if
they are needed.  Where dependencies cannot be avoidable, popular and
reliable CPAN modules, which are already available as packages in the
major Linux vendors (Debian, Red Hat) should be preferred.

As such L<Alien::Build> is hyper aggressive at using dynamic
prerequisites.

=head3 interface agnostic

One of the challenges with L<Alien::Buil::ModuleBuild> was that
L<Module::Build> was pulled from the core.  In addition, there is a
degree of hostility toward L<Module::Build> in some corners of the Perl
community.  I agree with Joel Berger's rationale for choosing
L<Module::Build> at the time, as I believe its interface more easily
lends itself to building L<Alien> distributions.

That said, an important feature of L<Alien::Build> is that it is
installer agnostic.  Although it is initially designed to work with
L<ExtUtils::MakeMaker>, it has been designed from the ground up to work
with any installer (Perl, or otherwise).

As an extension of this, although L<Alien::Build> may have external CPAN
dependencies, they should not be exposed to developers USING
L<Alien::Build>.  As an example, L<Path::Tiny> is used heavily
internally because it does what L<File::Spec> does, plus the things that
it doesn't, and uses forward slashes on Windows (backslashes are the
"correct separator on windows, but actually using them tends to break
everything).  However, there aren't any interfaces in L<Alien::Build>
that will return a L<Path::Tiny> object (or if there are, then this is a
bug).

This means that if we ever need to port L<Alien::Build> to a platform
that doesn't support L<Path::Tiny> (such as VMS), then it may require
some work to L<Alien::Build> itself, modules that USE L<Alien::Build>
shouldn't need to be modified.

=head3 plugable

The actual logic that probes the system, downloads source and builds it
should be as pluggable as possible.  One of the challenges with
L<Alien::Build::ModuleBuild> was that it was designed to work well with
software that works with C<autoconf> and C<pkg-config>.  While you can
build with other tools, you have to know a bit of how the installer
logic works, and which hooks need to be tweaked.

L<Alien::Build> has plugins for C<autoconf>, C<pkgconf> (successor of
C<pkg-config>), vanilla Makefiles, and CMake.  If your build system
doesn't have a plugin, then all you have to do is write one!  Plugins
that prove their worth may be merged into the L<Alien::Build> core.
Plugins that after a while feel like maybe not such a good idea may be
removed from the core, or even from CPAN itself.

In addition, L<Alien::Build> has a special type of plugin, called a
negotiator which picks the best plugin for the particular environment
that it is running in.  This way, as development of the negotiator and
plugins develop over time modules that use L<Alien::Build> will benefit,
without having to change the way they interface with L<Alien::Build>

=head1 ACKNOWLEDGEMENT

I would like to that Joel Berger for getting things running in the first
place.  Also important to thank other members of the "Alien::Base team":

Zaki Mughal (SIVOAIS)

Ed J (ETJ, mohawk)

Also kind thanks to all of the developers who have contributed to
L<Alien::Base> over the years:

L<https://metacpan.org/pod/Alien::Base#CONTRIBUTORS>

=head1 SEE ALSO

L<alienfile>, L<Alien::Build::MM>, L<Alien::Build::Plugin>, L<Alien::Base>, L<Alien>

=head1 AUTHOR

Author: Graham Ollis E<lt>plicease@cpan.orgE<gt>

Contributors:

Diab Jerius (DJERIUS)

Roy Storey (KIWIROY)

Ilya Pavlov

David Mertens (run4flat)

Mark Nunberg (mordy, mnunberg)

Christian Walde (Mithaldu)

Brian Wightman (MidLifeXis)

Zaki Mughal (zmughal)

mohawk (mohawk2, ETJ)

Vikas N Kumar (vikasnkumar)

Flavio Poletti (polettix)

Salvador Fandiño (salva)

Gianni Ceccarelli (dakkar)

Pavel Shaydo (zwon, trinitum)

Kang-min Liu (劉康民, gugod)

Nicholas Shipp (nshp)

Juan Julián Merelo Guervós (JJ)

Joel Berger (JBERGER)

Petr Pisar (ppisar)

Lance Wicks (LANCEW)

Ahmad Fatoum (a3f, ATHREEF)

José Joaquín Atria (JJATRIA)

Duke Leto (LETO)

Shoichi Kaji (SKAJI)

Shawn Laffan (SLAFFAN)

Paul Evans (leonerd, PEVANS)

Håkon Hægland (hakonhagland, HAKONH)

nick nauwelaerts (INPHOBIA)

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2011-2020 by Graham Ollis.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut