Added a plugin system

dist.ini

@@ -1,5 +1,5 @@
 name = Devel-PatchPerl
-version = 0.62
+version = 0.64
 author = Chris Williams <chris@bingosnet.co.uk>
 license = Perl_5
 copyright_holder = Chris Williams and Marcus Holland-Moritz
@@ -12,3 +12,4 @@ File::pushd                     = 1.00
 IO::File                        = 0
 IPC::Cmd                        = 0.40
 MIME::Base64                    = 0
+Module::Pluggable               = 0

lib/Devel/PatchPerl.pm

@@ -9,6 +9,7 @@ use File::Spec;
 use IO::File;
 use IPC::Cmd qw[can_run run];
 use Devel::PatchPerl::Hints qw[hint_file];
+use Module::Pluggable search_path => ['Devel::PatchPerl::Plugin'];
 use vars qw[@ISA @EXPORT_OK];
 
 @ISA       = qw(Exporter);
@@ -161,9 +162,41 @@ sub patch_source {
          $sub->(@args);
        }
     }
+    _process_plugin( version => $vers, source => $source, patchexe => $patch_exe );
   }
 }
 
+sub _process_plugin {
+  my %args = @_;
+  return unless my $possible = $ENV{PERL5_PATCHPERL_PLUGIN};
+  my ($plugin) = grep { $possible eq $_ or /\Q$possible\E$/ } __PACKAGE__->plugins;
+  unless ( $plugin ) {
+    warn "# You specified a plugin '", $ENV{PERL5_PATCHPERL_PLUGIN},
+         "' that isn't installed, just thought you might be interested.\n";
+    return;
+  }
+  {
+    local $@;
+    eval "require $plugin";
+    if ($@) {
+      die "# I tried to load '", $ENV{PERL5_PATCHPERL_PLUGIN},
+          "' but it didn't work out. Here is what happened '$@'\n";
+    }
+  }
+  {
+    local $@;
+    eval {
+      $plugin->patchperl(
+        %args,
+      );
+    };
+    if ($@) {
+      warn "# Warnings from the plugin: '$@'\n";
+    }
+  }
+  return 1;
+}
+
 sub _is
 {
   my($s1, $s2) = @_;
@@ -1778,9 +1811,15 @@ current working directory.
 
 =back
 
+=head1 PLUGIN SYSTEM
+
+See L<Devel::PatchPerl::Plugin> for details of Devel::PatchPerl's plugin system.
+
 =head1 SEE ALSO
 
 L<Devel::PPPort>
 
+L<Devel::PatchPerl::Plugin>
+
 =cut
 

lib/Devel/PatchPerl/Plugin.pm

@@ -0,0 +1,67 @@
+package Devel::PatchPerl::Plugin;
+
+#ABSTRACT: Devel::PatchPerl plugins explained
+
+use strict;
+use warnings;
+
+qq[Plug it in];
+
+=pod
+
+=head1 DESCRIPTION
+
+This document explains the L<Devel::PatchPerl> plugin system.
+
+Plugins are a mechanism for providing additional functionality to
+L<Devel::PatchPerl>.
+
+Plugins are searched for in the L<Devel::PatchPerl::Plugin> namespace.
+
+=head1 INITIALISATION
+
+The plugin constructor is C<patchperl>.
+
+A plugin is specified using the C<PERL5_PATCHPERL_PLUGIN> environment
+variable. It may either be specified in full (ie. C<Devel::PatchPerl::Plugin::Feegle>)
+or as the short part (ie. C<Feegle>).
+
+  $ export PERL5_PATCHPERL_PLUGIN=Devel::PatchPerl::Plugin::Feegle
+
+  $ export PERL5_PATCHPERL_PLUGIN=Feegle
+
+When L<Devel::PatchPerl> has identified the perl source patch and done its patching
+it will attempt to load the plugin identified. It will then call the class method
+C<patchperl> for the plugin package, with the following parameters:
+
+  'version', the Perl version of the source tree;
+  'source', the absolute path to the Perl source tree;
+  'patchexe', the 'patch' utility that can be used;
+
+Plugins are called with the current working directory being the root of the
+Perl source tree, ie. C<source>.
+
+Summarised:
+
+  $ENV{PERL5_PATCHPERL_PLUGIN} = 'Devel::PatchPerl::Plugin::Feegle';
+
+  my $plugin = $ENV{PERL5_PATCHPERL_PLUGIN};
+
+  eval "require $plugin";
+
+  eval {
+    $plugin->patchperl( version => $vers, source => $srcdir, patchexe => $patch );
+  };
+
+=head1 WHAT CAN PLUGINS DO?
+
+Anything you desire to a Perl source tree.
+
+=head1 WHY USE AN ENVIRONMENT VARIABLE TO SPECIFY PLUGINS?
+
+So that indicating a plugin to use can be specified independently of whatever mechanism is
+calling L<Devel::PatchPerl> to do its bidding.
+
+Think L<perlbrew>.
+
+=cut

t/03_plugin.t

@@ -0,0 +1,11 @@
+use strict;
+use warnings;
+use lib 't/lib';
+BEGIN {
+  $ENV{PERL5_PATCHPERL_PLUGIN} = 'TEST';
+}
+use Test::More qq'no_plan';
+use File::Spec;
+use Devel::PatchPerl;
+my $result = Devel::PatchPerl::_process_plugin(version => '5.14.2');
+ok( $result, 'The result was okay' );

t/lib/Devel/PatchPerl/Plugin/TEST.pm

@@ -0,0 +1,10 @@
+package Devel::PatchPerl::Plugin::TEST;
+
+use strict;
+use warnings;
+
+sub patchperl {
+  warn "I AM A TEST PLUGIN\n";
+}
+
+qq[1];