Andrew's git - gitweb.git/blob - perl/Git/LoadCPAN.pm

   1package Git::LoadCPAN;
   2use 5.008;
   3use strict;
   4use warnings;
   5
   6=head1 NAME
   7
   8Git::LoadCPAN - Wrapper for loading modules from the CPAN (OS) or Git's own copy
   9
  10=head1 DESCRIPTION
  11
  12The Perl code in Git depends on some modules from the CPAN, but we
  13don't want to make those a hard requirement for anyone building from
  14source.
  15
  16Therefore the L<Git::LoadCPAN> namespace shipped with Git contains
  17wrapper modules like C<Git::LoadCPAN::Module::Name> that will first
  18attempt to load C<Module::Name> from the OS, and if that doesn't work
  19will fall back on C<FromCPAN::Module::Name> shipped with Git itself.
  20
  21Usually distributors will not ship with Git's Git::FromCPAN tree at
  22all via the C<NO_PERL_CPAN_FALLBACKS> option, preferring to use their
  23own packaging of CPAN modules instead.
  24
  25This module is only intended to be used for code shipping in the
  26C<git.git> repository. Use it for anything else at your peril!
  27
  28=cut
  29
  30# NO_PERL_CPAN_FALLBACKS_STR evades the sed search-replace from the
  31# Makefile, and allows for detecting whether the module is loaded from
  32# perl/Git as opposed to perl/build/Git, which is useful for one-off
  33# testing without having Error.pm et al installed.
  34use constant NO_PERL_CPAN_FALLBACKS_STR => '@@' . 'NO_PERL_CPAN_FALLBACKS' . '@@';
  35use constant NO_PERL_CPAN_FALLBACKS => (
  36        q[@@NO_PERL_CPAN_FALLBACKS@@] ne ''
  37        and
  38        q[@@NO_PERL_CPAN_FALLBACKS@@] ne NO_PERL_CPAN_FALLBACKS_STR
  39);
  40
  41sub import {
  42        shift;
  43        my $caller = caller;
  44        my %args = @_;
  45        my $module = exists $args{module} ? delete $args{module} : die "BUG: Expected 'module' parameter!";
  46        my $import = exists $args{import} ? delete $args{import} : die "BUG: Expected 'import' parameter!";
  47        die "BUG: Too many arguments!" if keys %args;
  48
  49        # Foo::Bar to Foo/Bar.pm
  50        my $package_pm = $module;
  51        $package_pm =~ s[::][/]g;
  52        $package_pm .= '.pm';
  53
  54        eval {
  55                require $package_pm;
  56                1;
  57        } or do {
  58                my $error = $@ || "Zombie Error";
  59
  60                if (NO_PERL_CPAN_FALLBACKS) {
  61                        chomp(my $error = sprintf <<'THEY_PROMISED', $module);
  62BUG: The '%s' module is not here, but NO_PERL_CPAN_FALLBACKS was set!
  63
  64Git needs this Perl module from the CPAN, and will by default ship
  65with a copy of it. This Git was built with NO_PERL_CPAN_FALLBACKS,
  66meaning that whoever built it promised to provide this module.
  67
  68You're seeing this error because they broke that promise, and we can't
  69load our fallback version, since we were asked not to install it.
  70
  71If you're seeing this error and didn't package Git yourself the
  72package you're using is broken, or your system is broken. This error
  73won't appear if Git is built without NO_PERL_CPAN_FALLBACKS (instead
  74we'll use our fallback version of the module).
  75THEY_PROMISED
  76                        die $error;
  77                }
  78
  79                my $Git_LoadCPAN_pm_path = $INC{"Git/LoadCPAN.pm"} || die "BUG: Should have our own path from %INC!";
  80
  81                require File::Basename;
  82                my $Git_LoadCPAN_pm_root = File::Basename::dirname($Git_LoadCPAN_pm_path) || die "BUG: Can't figure out lib/Git dirname from '$Git_LoadCPAN_pm_path'!";
  83
  84                require File::Spec;
  85                my $Git_pm_FromCPAN_root = File::Spec->catdir($Git_LoadCPAN_pm_root, '..', 'FromCPAN');
  86                die "BUG: '$Git_pm_FromCPAN_root' should be a directory!" unless -d $Git_pm_FromCPAN_root;
  87
  88                local @INC = ($Git_pm_FromCPAN_root, @INC);
  89                require $package_pm;
  90        };
  91
  92        if ($import) {
  93                no strict 'refs';
  94                *{"${caller}::import"} = sub {
  95                        shift;
  96                        use strict 'refs';
  97                        unshift @_, $module;
  98                        goto &{"${module}::import"};
  99                };
 100                use strict 'refs';
 101        }
 102}
 103
 1041;