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perl Git::LoadCPAN: emit better errors under NO_PERL_CPAN_FALLBACKS

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Before my 20d2a30f8f ("Makefile: replace perl/Makefile.PL with simple
make rules", 2017-12-10) on an OS package that removed the
private-Error.pm copy we carried around manually removing the OS's
Error.pm would yield:

    $ git add -p
    Can't locate Error.pm in @INC (you may need to install the Error module) [...]

Now, before this change we'll instead emit this more cryptic error:

    $ git add -p
    BUG: '/usr/share/perl5/Git/FromCPAN' should be a directory! at /usr/share/perl5/Git/Error.pm line 36.

This is a confusing error. Now if the new NO_PERL_CPAN_FALLBACKS
option is specified and we can't find the module we'll instead emit:

    $ /tmp/git/bin/git add -p
    BUG: The 'Error' module is not here, but NO_PERL_CPAN_FALLBACKS was set!

    [...]

Where [...] is the lengthy explanation seen in the change below, which
explains what the potential breakage is, and how to fix it.

The reason for checking @@NO_PERL_CPAN_FALLBACKS@@] against the empty
string in Perl is as opposed to checking for a boolean value is that
that's (as far as I can tell) make's idea of a string that's set, and
e.g. NO_PERL_CPAN_FALLBACKS=0 is enough to set NO_PERL_CPAN_FALLBACKS.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Ævar Arnfjörð Bjarmason
2018-03-03 15:38:17 +00:00
committed by Junio C Hamano
parent 075321c007
commit 1aca69c019
3 changed files with 44 additions and 5 deletions
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33
perl/Git/LoadCPAN.pm
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@ -19,13 +19,25 @@ 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, preferring to use their own packaging of CPAN modules instead.
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;
@ -45,6 +57,25 @@ sub import {
} 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;