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Diffstat (limited to 'perl/Git/LoadCPAN.pm')
| -rw-r--r-- | perl/Git/LoadCPAN.pm | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/perl/Git/LoadCPAN.pm b/perl/Git/LoadCPAN.pm new file mode 100644 index 000000000000..e5585e75e809 --- /dev/null +++ b/perl/Git/LoadCPAN.pm @@ -0,0 +1,104 @@ +package Git::LoadCPAN; +use 5.008; +use strict; +use warnings; + +=head1 NAME + +Git::LoadCPAN - Wrapper for loading modules from the CPAN (OS) or Git's own copy + +=head1 DESCRIPTION + +The Perl code in Git depends on some modules from the CPAN, but we +don't want to make those a hard requirement for anyone building from +source. + +Therefore the L<Git::LoadCPAN> namespace shipped with Git contains +wrapper modules like C<Git::LoadCPAN::Module::Name> that will first +attempt to load C<Module::Name> from the OS, and if that doesn't work +will fall back on C<FromCPAN::Module::Name> shipped with Git itself. + +Usually distributors will not ship with Git's Git::FromCPAN tree at +all via the C<NO_PERL_CPAN_FALLBACKS> option, preferring to use their +own packaging of CPAN modules instead. + +This module is only intended to be used for code shipping in the +C<git.git> repository. Use it for anything else at your peril! + +=cut + +# NO_PERL_CPAN_FALLBACKS_STR evades the sed search-replace from the +# Makefile, and allows for detecting whether the module is loaded from +# perl/Git as opposed to perl/build/Git, which is useful for one-off +# testing without having Error.pm et al installed. +use constant NO_PERL_CPAN_FALLBACKS_STR => '@@' . 'NO_PERL_CPAN_FALLBACKS' . '@@'; +use constant NO_PERL_CPAN_FALLBACKS => ( + q[@@NO_PERL_CPAN_FALLBACKS@@] ne '' + and + q[@@NO_PERL_CPAN_FALLBACKS@@] ne NO_PERL_CPAN_FALLBACKS_STR +); + +sub import { + shift; + my $caller = caller; + my %args = @_; + my $module = exists $args{module} ? delete $args{module} : die "BUG: Expected 'module' parameter!"; + my $import = exists $args{import} ? delete $args{import} : die "BUG: Expected 'import' parameter!"; + die "BUG: Too many arguments!" if keys %args; + + # Foo::Bar to Foo/Bar.pm + my $package_pm = $module; + $package_pm =~ s[::][/]g; + $package_pm .= '.pm'; + + eval { + require $package_pm; + 1; + } or do { + my $error = $@ || "Zombie Error"; + + if (NO_PERL_CPAN_FALLBACKS) { + chomp(my $error = sprintf <<'THEY_PROMISED', $module); +BUG: The '%s' module is not here, but NO_PERL_CPAN_FALLBACKS was set! + +Git needs this Perl module from the CPAN, and will by default ship +with a copy of it. This Git was built with NO_PERL_CPAN_FALLBACKS, +meaning that whoever built it promised to provide this module. + +You're seeing this error because they broke that promise, and we can't +load our fallback version, since we were asked not to install it. + +If you're seeing this error and didn't package Git yourself the +package you're using is broken, or your system is broken. This error +won't appear if Git is built without NO_PERL_CPAN_FALLBACKS (instead +we'll use our fallback version of the module). +THEY_PROMISED + die $error; + } + + my $Git_LoadCPAN_pm_path = $INC{"Git/LoadCPAN.pm"} || die "BUG: Should have our own path from %INC!"; + + require File::Basename; + 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'!"; + + require File::Spec; + my $Git_pm_FromCPAN_root = File::Spec->catdir($Git_LoadCPAN_pm_root, '..', 'FromCPAN'); + die "BUG: '$Git_pm_FromCPAN_root' should be a directory!" unless -d $Git_pm_FromCPAN_root; + + local @INC = ($Git_pm_FromCPAN_root, @INC); + require $package_pm; + }; + + if ($import) { + no strict 'refs'; + *{"${caller}::import"} = sub { + shift; + use strict 'refs'; + unshift @_, $module; + goto &{"${module}::import"}; + }; + use strict 'refs'; + } +} + +1; |