Merge branch 'tz/exclude-doc-smallfixes'
[git/git.git] / perl / Git / LoadCPAN.pm
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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
382029fc 19will fall back on C<FromCPAN::Module::Name> shipped with Git itself.
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20
21Usually distributors will not ship with Git's Git::FromCPAN tree at
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22all via the C<NO_PERL_CPAN_FALLBACKS> option, preferring to use their
23own packaging of CPAN modules instead.
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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
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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
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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
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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
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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;
382029fc 85 my $Git_pm_FromCPAN_root = File::Spec->catdir($Git_LoadCPAN_pm_root, '..', 'FromCPAN');
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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;