<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">NAME

    Alien::Build - Build external dependencies for use in CPAN

VERSION

    version 0.01

SYNOPSIS

    TODO

DESCRIPTION

    NOTE: This is still experimental, and documentation is currently highly
    incomplete.

    This module provides tools for building external (non-CPAN)
    dependencies for CPAN. It is mainly designed to be used at install time
    of a CPAN client, and work closely with Alien::Base which is used at
    runtime.

CONSTRUCTOR

 new

     my $build = Alien::Build-&gt;new;

PROPERTIES

 meta_prop

     my $href = $build-&gt;meta_prop;
     my $href = Alien::Build-&gt;meta_prop;

    Hash of class properties.

    destdir

      Use the DESTDIR environment variable to stage your install before
      copying the files into blib. This is the preferred method of
      installing libraries because it improves reliability. This technique
      is supported by autoconf and others.

 install_prop

     my $href = $build-&gt;install_prop;

    Hash of properties used during the install phase, for either a system
    or share install. For most things you will want to use runtime_prop
    below. Only use install_prop for properties that are needed ONLY during
    the install phase. Standard properties:

    root

      The build root directory. This will be an absolute path. It is the
      absolute form of ./_alien by default.

    prefix

      The install time prefix. This may or may not be the same as the
      runtime prefix. It may or may not be the same as stage.

    stage

      The stage directory where files will be copied. This is usually the
      root of the blib share directory.

    NOTE: These properties should not include any blessed objects or code
    references, because they will be serialized using a method that does
    not preserve those capabilities.

 runtime_prop

     my $href = $build-&gt;runtime_prop;

    Hash of properties used during the runtime phase. This can include
    anything needed by your Alien::Base based module, but these are
    frequently useful:

    cflags

      The compiler flags

    libs

      The library flags

    version

      The version of the library or tool

    prefix

      The final install root.

    install_type

      The install type. Is one of:

      system

	For when the library or tool is provided by the operating system,
	can be detected by Alien::Build, and is considered satisfactory by
	the alienfile recipe.

      share

	For when a system install is not possible, the library source will
	be downloaded from the internet or retrieved in another appropriate
	fashion and built.

    NOTE: These properties should not include any blessed objects or code
    references, because they will be serialized using a method that does
    not preserve those capabilities.

 root

     my $dir = $build-&gt;root;

    This is just a shortcut for:

     my $root = $build-&gt;install_prop-&gt;{root};

    Except that it will be created if it does not already exist.

 install_type

     my $type = $build-&gt;install_type;

    This is just a shortcut for:

     my $type = $build-&gt;runtime_prop-&gt;{install_type};

METHODS

 set_prefix

     $build-&gt;set_prefix($prefix);

 load

     my $build = Alien::Build-&gt;load($alienfile);

 checkpoint

     $build-&gt;checkpoint;

    Save any install or runtime properties so that they can be reloaded on
    a subsequent run.

 resume

     Alien::Build-&gt;resume($alienfile, $root);

 requires

     my $hash = $build-&gt;requires($phase);

 load_requires

     $build-&gt;load_requires;

 meta

     my $meta = Alien::Build-&gt;meta;
     my $meta = $build-&gt;meta;

 probe

     my $install_type = $build-&gt;probe;

    Attempts to determine if the operating system has the library or tool
    already installed. If so, then the string system will be returned and a
    system install will be performed. If not, then the string share will be
    installed and the tool or library will be downloaded and built from
    source.

    If the environment variable ALIEN_INSTALL_TYPE is set, then that will
    be used instead of the detection logic.

 gather_system

     $build-&gt;gather_system

    This method gathers the necessary properties from the system for using
    the library or tool under a system install type.

 download

     $build-&gt;download;

 fetch

     my $res = $build-&gt;fetch;
     my $res = $build-&gt;fetch($url);

    Fetch a resource using the fetch hook. Returns the same hash structure
    described below in the hook documentation.

 decode

     my $decoded_res = $build-&gt;decode($res);

    Decode the HTML or file listing returned by fetch.

 prefer

     my $sorted_res = $build-&gt;prefer($res);

    Filter and sort candidates. The preferred candidate will be returned
    first in the list. The worst candidate will be returned last.

 extract

     my $dir = $build-&gt;extract;
     my $dir = $build-&gt;extract($archive);

 build

     $build-&gt;build;

HOOKS

 probe hook

     $meta-&gt;register_hook( probe =&gt; sub {
       my($build) = @_;
       return 'system' if ...; # system install
       return 'share';         # otherwise
     });
     
     $meta-&gt;register_hook( probe =&gt; [ $command ] );

    This hook should return the string system if the operating system
    provides the library or tool. It should return share otherwise.

    You can also use a command that returns true when the tool or library
    is available. For example for use with pkg-config:

     $meta-&gt;register_hook( probe =&gt;
       [ '%{pkgconf} --exists libfoo' ] );

    Or if you needed a minimum version:

     $meta-&gt;register_hook( probe =&gt;
       [ '%{pkgconf} --atleast-version=1.00 libfoo' ] );

    Note that this hook SHOULD NOT gather system properties, such as
    cflags, libs, versions, etc, because the probe hook will be skipped in
    the even the environment variable ALIEN_INSTALL_TYPE is set. The
    detection of these properties should instead be done by the
    gather_system hook, below.

 gather_system hook

     $meta-&gt;register_hook( gather_system =&gt; sub {
       my($build) = @_;
       $build-&gt;runtime_prop-&gt;{cflags}  = ...;
       $build-&gt;runtime_prop-&gt;{libs}    = ...;
       $build-&gt;runtime_prop-&gt;{version} = ...;
     });

    This hook is called for a system install to determine the properties
    necessary for using the library or tool. These properties should be
    stored in the runtime_prop hash as shown above. Typical properties that
    are needed for libraries are cflags and libs. If at all possible you
    should also try to determine the version of the library or tool.

 download hook

     $meta-&gt;register_hook( download =&gt; sub {
       my($build) = @_;
     });

    This hook is used to download from the internet the source. Either as
    an archive (like tar, zip, etc), or as a directory of files (git clone,
    etc). When the hook is called, the current working directory will be a
    new empty directory, so you can save the download to the current
    directory. If you store a single file in the directory, Alien::Build
    will assume that it is an archive, which will be processed by the
    extract hook below. If you store multiple files, Alien::Build will
    assume the current directory is the source root. If no files are stored
    at all, an exception with an appropriate diagnostic will be thrown.

    Note: If you register this hook, then the fetch, decode and prefer
    hooks will NOT be called.

 fetch hook

     package Alien::Build::Plugin::MyPlugin;
     
     use strict;
     use warnings;
     use Alien::Build::Plugin;
     use Carp ();
     
     has '+url' =&gt; sub { Carp::croak "url is required property" };
    
     sub init
     {
       my($self, $meta) = @_;
       
       $meta-&gt;register_hook( fetch =&gt; sub {
         my($build, $url) = @_;
         ...
       }
     }
     
     1;

    Used to fetch a resource. The first time it will be called without an
    argument, so the configuration used to find the resource should be
    specified by the plugin's properties. On subsequent calls the first
    argument will be a URL.

    Normally the first fetch will be to either a file or a directory
    listing. If it is a file then the content should be returned as a hash
    reference with the following keys:

     # content of file stored in Perl
     return {
       type     =&gt; 'file',
       filename =&gt; $filename,
       content  =&gt; $content,
     };
     
     # content of file stored in the filesystem
     return {
       type     =&gt; 'file',
       filename =&gt; $filename,
       path     =&gt; $path,    # full file system path to file
     };

    If the URL points to a directory listing you should return it as either
    a hash reference containing a list of files:

     return {
       type =&gt; 'list',
       list =&gt; [
         # filename: each filename should be just the
         #   filename portion, no path or url.
         # url: each url should be the complete url
         #   needed to fetch the file.
         { filename =&gt; $filename1, url =&gt; $url1 },
         { filename =&gt; $filename2, url =&gt; $url2 },
       ]
     };

    or if the listing is in HTML format as a hash reference containing the
    HTML information:

     return {
       type =&gt; 'html',
       charset =&gt; $charset, # optional
       base    =&gt; $base,    # the base URL: used for computing relative URLs
       content =&gt; $content, # the HTML content
     };

    or a directory listing (usually produced by ftp servers) as a hash
    reference:

     return {
       type    =&gt; 'dir_listing',
       base    =&gt; $base,
       content =&gt; $content,
     };

 decode hook

     sub init
     {
       my($self, $meta) = @_;
       
       $meta-&gt;register_hook( decode =&gt; sub {
         my($build, $res) = @_;
         ...
       }
     }

    This hook takes a response hash reference from the fetch hook above
    with a type of html or dir_listing and converts it into a response hash
    reference of type list. In short it takes an HTML or FTP file listing
    response from a fetch hook and converts it into a list of filenames and
    links that can be used by the prefer hook to choose the correct file to
    download. See fetch for the specification of the input and response
    hash references.

 prefer hook

     sub init
     {
       my($self, $meta) = @_;
       
       $meta-&gt;register_hook( prefer =&gt; sub {
         my($build, $res) = @_;
         return {
           type =&gt; 'list',
           list =&gt; [sort @{ $res-&gt;{list} }],
         };
       }
     }

    This hook sorts candidates from a listing generated from either the
    fetch or decode hooks. It should return a new list hash reference with
    the candidates sorted from best to worst. It may also remove candidates
    that are totally unacceptable.

 extract hook

     $meta-&gt;register_hook( extract =&gt; sub {
       my($build, $archive) = @_;
       ...
     });

 build hook

     $meta-&gt;register_hook( build =&gt; sub {
       my($build) = @_;
       ...
     });

 gather_share hook

     $meta-&gt;register_hook( register_hook =&gt; sub {
       my($build) = @_;
       ... 
     });

META METHODS

 prop

     my $href = $build-&gt;meta-&gt;prop;
     my $href = Alien::Build-&gt;meta-&gt;prop;

    Meta properties. This is the same as calling meta_prop on the class or
    Alien::Build instance.

 filename

     my $filename = $build-&gt;meta-&gt;filename;
     my $filename = Alien::Build-&gt;meta-&gt;filename;

 add_requires

     $build-&gt;meta-&gt;add_requires($phase, $module =&gt; $version, ...);
     Alien::Build-&gt;meta-&gt;add_requires($phase, $module =&gt; $version, ...);

 interpolator

     my $interpolator = $build-&gt;meta-&gt;interpolator;
     my $interpolator = Alien::Build-&gt;interpolator;

 has_hook

     my $bool = $build-&gt;meta-&gt;has_hook($name);
     my $bool = Alien::Build-&gt;has_hook($name);

 register_hook

     $build-&gt;meta-&gt;register_hook($name, $instructions);
     Alien::Build-&gt;meta-&gt;register_hook($name, $instructions);

 default_hook

     $build-&gt;meta-&gt;default_hook($name, $instructions);
     Alien::Build-&gt;meta-&gt;default_hook($name, $instructions);

 around_hook

     $build-&gt;meta-&gt;around_hook($hook, $code);
     Alien::Build-&gt;meta-&gt;around_hook($name, $code);

CONTRIBUTING

    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:

    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 Alien::Build developers, and the best way to
    contact them is on the #native IRC channel on irc.perl.org.

 History

    Joel Berger wrote the original Alien::Base. This distribution included
    the runtime code Alien::Base and an installer class
    Alien::Base::ModuleBuild. The significant thing about Alien::Base was
    that it provided tools to make it relatively easy for people to roll
    their own Alien distributions. Over time, the Perl5-Alien (github
    organization) or "Alien::Base team" has taken over development of
    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 Alien::Base, Module::Build, on which
    Alien::Base::ModuleBuild is based, has been removed from the core of
    Perl. It seemed worthwhile to write a replacement installer that works
    with 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.

 Philosophy

  avoid dependencies

    One of the challenges with 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 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 Alien::Build is hyper aggressive at using dynamic
    prerequisites.

  interface agnostic

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

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

    As an extension of this, although Alien::Build may have external CPAN
    dependencies, they should not be exposed to developers USING
    Alien::Build. As an example, Path::Tiny is used heavily internally
    because it does what 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 Alien::Build that
    will return a Path::Tiny object (or if there are, then this is a bug).

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

  plugable

    The actual logic that probes the system, downloads source and builds it
    should be as pluggable as possible. One of the challenges with
    Alien::Build::ModuleBuild was that it was designed to work well with
    software that works with autoconf and 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.

    Alien::Build has plugins for autoconf, pkgconf (successor of
    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 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, 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 Alien::Build will benefit,
    without having to change the way they interface with Alien::Build

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
    Alien::Base over the years:

    https://metacpan.org/pod/Alien::Base#CONTRIBUTORS

AUTHOR

    Graham Ollis &lt;plicease@cpan.org&gt;

COPYRIGHT AND LICENSE

    This software is copyright (c) 2017 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.

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