I have code that depends on Scalar::Util::weaken, which is only available if the XS version of Scalar::Util is installed. I'd like to gracefully detect if weaken isn't available and handle that in a sane way. That's easy enough to do.

My challenge is this: how do I test that error handling if I have the XS version installed? What is a limited way to test what happens when an XS version of a module is not available? How can I prevent the XS from being loaded for one particular module? (Without having a whole separate Perl installation.)

One idea I had was to override DynaLoader::bootstrap to just die -- which causes Scalar::Util to note the failure to bootstrap and likewise die with an appropriate warning about weaken not being available.

use strict;
use warnings;
use Test::More tests => 1;

BEGIN {
    eval{ require DynaLoader };
    no warnings 'redefine';
    *DynaLoader::bootstrap = sub { die };
}

eval "use Scalar::Util qw( weaken )";

like( $@, qr/\AWeak references are not implemented/, 
    "Catch unavailable weaken" );

[download]

(If necessary, this could be more targeted by checking which module is being bootstrapped and dying or going to the original bootstrap as appropriate.)

Is this safe? Sane? Have I overlooked some easier way of doing this? Is there some module on CPAN that makes this easier?

Feedback greatly appreciated.

update: The same technique applies for XSLoader::load.

-xdg

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In reply to Breaking XS for testing? by xdg

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