name : PluginAuthor.pod # PODNAME: Alien::Build::Manual::PluginAuthor # ABSTRACT: Alien::Build plugin author documentation # VERSION __END__ =pod =encoding UTF-8 =head1 NAME Alien::Build::Manual::PluginAuthor - Alien::Build plugin author documentation =head1 VERSION version 2.83 =head1 SYNOPSIS your plugin: package Alien::Build::Plugin::Build::MyPlugin; use strict; use warnings; use Alien::Build::Plugin; has arg1 => 'default_for arg1'; has arg2 => sub { [ 'default', 'for', 'arg2' ] }; sub init { my($self, $meta) = @_; ... } 1; and then from L<alienfile>: use alienfile; plugin 'Build::MyPlugin' => ( arg1 => 'override for arg1', arg2 => [ 'something', 'else' ], ); =for html <p>flowchart</p> <div style="display: flex"><div style="margin: 3px; flex: 1 1 50%"> <img src="image/PluginAuthor-flowchart.png" style="max-width: 100%"> </div></div> <p><b>Notes</b>: The colored blocks indicate <tt>alienfile</tt> blocks. Hooks are indicated as predefined process (rectangle with double struck vertical edges). Hooks that can easily be implemented from an <tt>alienfile</tt> are indicated in blue (Note that <tt>[]</tt> is used to indicate passing in an array reference, but a subroutine reference can also be used). For simplicity, the the flowchart does not include when required modules are loaded. Except for configure time requirements, they are loaded when the corresponding <tt>alienfile</tt> blocks are entered. It is not shown, but generally any plugin can cause a <b>Fail</b> by throwing an exception with <tt>die</tt>.</p> Perlish pseudo code for how plugins are called: my $probe; my $override = override(); if($override eq 'system') { $probe = probe(); if($probe ne 'system') { die 'system tool or library not found'; } } elsif($override eq 'default') { $probe = probe(); } else { # $override eq 'share' # note that in this instance the # probe hook is never called $probe = 'share'; } if($probe eq 'system') { gather_system(); } else { # $probe eq 'share' download(); extract(); patch(); build(); gather_share(); # Check to see if there isa build_ffi hook if(defined &build_ffi) { patch_ffi(); build_ffi(); gather_ffi(); } } # By default this just returns the value of $ENV{ALIEN_INSTALL_TYPE} sub override { return $ENV{ALIEN_INSTALL_TYPE}; } # Default download implementation; can be # replaced by specifying a different download # hook. See Alien::Build::Plugin::Core::Download # for detailed implementation. sub download { my $response = fetch(); if($response->{type} eq 'html' || $response->{type} eq 'dir_listing') { # decode will transform an HTML listing (html) or a FTP directory # listing (dir_listing) into a regular list $response = decode($response); } if($response->{type} eq 'list') { # prefer will filter bad entries in the list # and sort them so that the first one is # the one that we want $response = prefer($response); my $first_preferred = $res->{list}->[0]; # prefer can sometimes infer the version from the # filename. if(defined $first_preferred->{version}) { # not a hook runtime_prop->{version} = $first_preferred->{version}; } $response = fetch($first_preferred); } if($response->{type} eq 'file') { # not a hook write_file_to_disk $response; } } =head1 DESCRIPTION This document explains how to write L<Alien::Build> plugins using the L<Alien::Build::Plugin> base class. =head2 Writing plugins Plugins use L<Alien::Build::Plugin>, which sets the appropriate base class, and provides you with the C<has> property builder. C<has> takes two arguments, the name of the property and the default value. (As with L<Moose> and L<Moo>, you should use a code reference to specify default values for non-string defaults). No B<not> set this as your plugin's base class directly: use parent qw( Alien::Build::Plugin ); # wrong use Alien::Build::Plugin; # right The only method that you need to implement is C<init>. From this method you can add hooks to change the behavior of the L<alienfile> recipe. This is a very simple example of a probe hook, with the actual probe logic removed: sub init { my($self, $meta) = @_; $meta->register_hook( probe => sub { my($build) = @_; if( ... ) { return 'system'; } else { return 'share'; } }, ); } Hooks get the L<Alien::Build> instance as their first argument, and depending on the hook may get additional arguments. =head2 Modifying hooks You can also modify hooks using C<before_hook>, C<around_hook> and C<after_hook>, similar to L<Moose> modifiers: sub init { my($self, $meta) = @_; $meta->before_hook( build => sub { my($build) = @_; $build->log('this runs before the build'); }, ); $meta->after_hook( build => sub { my($build) = @_; $build->log('this runs after the build'); }, ); $meta->around_hook( build => sub { my $orig = shift; # around hooks are useful for setting environment variables local $ENV{CPPFLAGS} = '-I/foo/include'; $orig->(@_); }, ); } =head2 Testing plugins You can and should write tests for your plugin. The best way to do this is using L<Test::Alien::Build>, which allows you to write an inline L<alienfile> in your test. Here is an example: use Test::V0; use Test::Alien::Build; my $build = alienfile_ok q{ use alienfile; plugin 'Build::MyPlugin' => ( arg1 => 'override for arg1', arg2 => [ 'something', 'else' ], ); ... }; # you can interrogate $build, it is an instance of L<Alien::Build>. my $alien = alien_build_ok; # you can interrogate $alien, it is an instance of L<Alien::Base>. =head2 Negotiator plugins A Negotiator plugin doesn't itself typically implement anything on its own, but picks the best plugin to achieve a particular goal. The "best" plugin can in some cases vary depending on the platform or tools that are available. For example The L<download negotiator|Alien::Build::Plugin::Download::Negotiate> might choose to use the fetch plugin that relies on the command line C<curl>, or it might choose the fetch plugin that relies on the Perl module L<HTTP::Tiny> depending on the platform and what is already installed. (For either to be useful they have to support SSL). The Negotiator plugin is by convention named something like C<Alien::Build::Plugin::*::Negotiate>, but is typically invoked without the C<::Negotiate> suffix. For example: plugin 'Download'; # is short for Alien::Build::Plugin::Download::Negotiator Here is a simple example of a negotiator which picks C<curl> if already installed and L<HTTP::Tiny> otherwise. (The actual download plugin is a lot smarter and complicated than this, but this is a good simplified example). package Alien::Build::Plugin::Download::Negotiate; use strict; use warnings; use Alien::Build::Plugin; use File::Which qw( which ); sub init { my($self, $meta) = @_; if(which('curl')) { $meta->apply_plugin('Fetch::Curl'); } else { $meta->apply_plugin('Fetch::HTTPTiny'); } } =head2 Hooks The remainder of this document is a reference for the hooks that you can register. Generally speaking you can register any hook that you like, but some care must be taken as some hooks have default behavior that will be overridden when you register a hook. The hooks are presented in alphabetical order. The execution order is shown in the flowchart above (if you are browsing the HTML version of this document), or the Perlish pseudo code in the synopsis section. =head1 HOOKS =head2 build hook $meta->register_hook( build => sub { my($build) = @_; ... }); This does the main build of the alienized project and installs it into the staging area. The current directory is the build root. You need to run whatever tools are necessary for the project, and install them into C<$build->install_prop->{prefix}> (C<%{.install.prefix}>). =head2 build_ffi hook $meta->register_hook( build_ffi => sub { my($build) = @_; ... }); This is the same as L<build|/"build hook">, except it fires only on a FFI build. =head2 decode hook $meta->register_hook( decode => sub { my($build, $res) = @_; ... } This hook takes a response hash reference from the C<fetch> hook above with a type of C<html> or C<dir_listing> and converts it into a response hash reference of type C<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 the L<fetch hook|/"fetch hook"> for the specification of the input and response hash references. =head2 check_digest hook # implement the well known FOO-92 digest $meta->register_hook( check_digest => sub { my($build, $file, $algorithm, $digest) = @_; if($algorithm ne 'FOO92') { return 0; } my $actual = foo92_hex_digest($file); if($actual eq $digest) { return 1; } else { die "Digest FOO92 does not match: got $actual, expected $digest"; } }); This hook should check the given C<$file> (the format is the same as used by L<the fetch hook|/"fetch hook">) matches the given C<$digest> using the given C<$algorithm>. If the plugin does not support the given algorithm, then it should return a false value. If the digest does not match, it should throw an exception. If the digest matches, it should return a true value. =head2 clean_install $meta->register_hook( clean_install => sub { my($build) = @_; }); This hook allows you to remove files from the final install location before the files are installed by the installer layer (examples: L<Alien::Build::MM>, L<Alien::Build::MB> or L<App::af>). This hook is not called by default, and must be enabled via the interface to the installer layer (example: L<Alien::Build::MM/clean_install>). This hook SHOULD NOT remove the C<_alien> directory or its content from the install location. The default implementation removes all the files EXCEPT the C<_alien> directory and its content. =head2 download hook $meta->register_hook( download => sub { my($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 (C<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, L<Alien::Build> will assume that it is an archive, which will be processed by the L<extract hook|/"extract hook">. If you store multiple files, L<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. B<Note>: If you register this hook, then the fetch, decode and prefer hooks will NOT be called, unless you call them yourself from this hook. =head2 extract hook $meta->register_hook( extract => sub { my($build, $archive) = @_; ... }); This hook is used to extract an archive that has already been downloaded. L<Alien::Build> already has plugins for the most common archive formats, so you will likely only need this to add support for new or novel archive formats. When this hook is called, the current working directory will be a new empty directory, so you can save the content of the archive to the current directory. If a single directory is written to the current directory, L<Alien::Build> will assume that is the root directory of the package. If multiple files and/or directories are present, that will indicate that the current working directory is the root of the package. The logic typically handles correctly the default behavior for tar (where packages are typically extracted to a subdirectory) and for zip (where packages are typically extracted to the current directory). =head2 fetch hook package Alien::Build::Plugin::MyPlugin; use strict; use warnings; use Alien::Build::Plugin; use Carp (); has '+url' => sub { Carp::croak "url is required property" }; sub init { my($self, $meta) = @_; $meta->register_hook( fetch => sub { my($build, $url, %options) = @_; ... } } 1; Used to fetch a resource. The first time it will be called without an argument (or with C<$url> set to C<undef>, 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. The C<%options> hash may contain these options: =over 4 =item http_headers HTTP request headers, if an appropriate protocol is being used. The headers are provided as an array reference of key/value pairs, which allows for duplicate header keys with multiple values. If a non-HTTP protocol is used, or if the plugin cannot otherwise send HTTP request headers, the plugin SHOULD issue a warning using the C<< $build->log >> method, but because this option wasn't part of the original spec, the plugin MAY no issue that warning while ignoring it. =back Note that versions of L<Alien::Build> prior to 2.39 did not pass the options hash into the fetch plugin. 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 => 'file', filename => $filename, content => $content, version => $version, # optional, if known protocol => $protocol, # AB 2.60 optional, but recommended }; # content of file stored in the filesystem return { type => 'file', filename => $filename, path => $path, # full file system path to file version => $version, # optional, if known tmp => $tmp, # optional protocol => $protocol, # AB 2.60 optional, but recommended }; C<$tmp> if set will indicate if the file is temporary or not, and can be used by L<Alien::Build> to save a copy in some cases. The default is true, so L<Alien::Build> assumes the file or directory is temporary if you don't tell it otherwise. Probably the most common situation when you would set C<tmp> to false, is when the file is bundled inside the L<Alien> distribution. See L<Alien::Build::Plugin::Fetch::Local> for example. If the URL points to a directory listing you should return it as either a hash reference containing a list of files: return { type => 'list', list => [ # 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. # version: OPTIONAL, may be provided by some fetch or prefer { filename => $filename1, url => $url1, version => $version1 }, { filename => $filename2, url => $url2, version => $version2 }, ], protocol => $protocol, # AB 2.60 optional, but recommended }; or if the listing is in HTML format as a hash reference containing the HTML information: return { type => 'html', charset => $charset, # optional base => $base, # the base URL: used for computing relative URLs content => $content, # the HTML content protocol => $protocol, # optional, but recommended }; or a directory listing (usually produced by an FTP servers) as a hash reference: return { type => 'dir_listing', base => $base, content => $content, protocol => $protocol, # AB 2.60 optional, but recommended }; [version 2.60] For all of these responses C<$protocol> is optional, since it was not part of the original spec, however it is strongly recommended that you include this field, because future versions of L<Alien::Build> will use this to determine if a file was downloaded securely (that is via a secure protocol such as SSL). Some plugins (like L<decode plugins |Alien::Build::Plugin::Decode>) trans late a file hash from one type to another, they should maintain the C<$protocol> from the old to the new representation of the file. =head2 gather_ffi hook $meta->register_hook( gather_ffi => sub { my($build) = @_; $build->runtime_prop->{cflags} = ...; $build->runtime_prop->{libs} = ...; $build->runtime_prop->{version} = ...; }); This hook is called for a FFI build to determine the properties necessary for using the library or tool. These properties should be stored in the L<runtime_prop|Alien::Build/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. =head2 gather_share hook $meta->register_hook( gather_share => sub { my($build) = @_; $build->runtime_prop->{cflags} = ...; $build->runtime_prop->{libs} = ...; $build->runtime_prop->{version} = ...; }); This hook is called for a share install to determine the properties necessary for using the library or tool. These properties should be stored in the L<runtime_prop|Alien::Build/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. =head2 gather_system hook $meta->register_hook( gather_system => sub { my($build) = @_; $build->runtime_prop->{cflags} = ...; $build->runtime_prop->{libs} = ...; $build->runtime_prop->{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 L<runtime_prop|Alien::Build/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. =head2 override hook $meta->register_hook( override => sub { my($build) = @_; return $ENV{ALIEN_INSTALL_TYPE} || ''; }); This allows you to alter the override logic. It should return one of C<share>, C<system>, C<default> or C<''>. The default implementation is shown above. L<Alien::Build::Plugin::Probe::Override> and L<Alien::Build::Plugin::Probe::OverrideCI> are examples of how you can use this hook. =head2 patch hook $meta->register_hook( patch => sub { my($build) = @_; ... }); This hook is completely optional. If registered, it will be triggered after extraction and before build. It allows you to apply any patches or make any modifications to the source if they are necessary. =head2 patch_ffi hook $meta->register_hook( patch_ffi => sub { my($build) = @_; ... }); This hook is exactly like the L<patch hook|/"patch hook">, except it fires only on an FFI build. =head2 prefer hook $meta->register_hook( prefer => sub { my($build, $res) = @_; return { type => 'list', list => [sort @{ $res->{list} }], }; } This hook sorts candidates from a listing generated from either the C<fetch> or C<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. =head2 probe hook $meta->register_hook( probe => sub { my($build) = @_; return 'system' if ...; # system install return 'share'; # otherwise }); $meta->register_hook( probe => [ $command ] ); This hook should return the string C<system> if the operating system provides the library or tool. It should return C<share> otherwise. You can also use a command that returns true when the tool or library is available. For example for use with C<pkg-config>: $meta->register_hook( probe => [ '%{pkgconf} --exists libfoo' ] ); Or if you needed a minimum version: $meta->register_hook( probe => [ '%{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 event the environment variable C<ALIEN_INSTALL_TYPE> is set. The detection of these properties should instead be done by the L<gather_system|/"gather_system hook"> hook. Multiple probe hooks can be given. These will be used in sequence, stopping at the first that detects a system installation. =head1 SEE ALSO =over 4 =item L<Alien::Build::Manual> Other L<Alien::Build> manuals. =back =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 Písař (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) Florian Weimer =head1 COPYRIGHT AND LICENSE This software is copyright (c) 2011-2022 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