Perl: mocking -d -f and friends. How to put them into CORE::GLOBAL

Question

The CORE documentation has shown me how to merrily mock various built Perl functions. However, I'm not really sure how to replace '-d' &c. with my methods. So this is really just a question on how do i replace a function with a dash in it in CORE::GLOBAL.

A manual reference would be nice.

package Testing::MockDir;

use strict;
use warnings;
use Exporter();
use Symbol 'qualify_to_ref';

*import = \&Exporter::import;

our @EXPORT_OK = qw(SetMockDir UnsetMockDir);

our %EXPORT_TAGS = (
    'all' => \@EXPORT_OK,
);

my %path2List = ();
my %handle2List = ();

BEGIN {
    *CORE::GLOBAL::opendir = \&Testing::MockDir::opendir;
    *CORE::GLOBAL::readdir = \&Testing::MockDir::readdir;
    *CORE::GLOBAL::closedir = \&Testing::MockDir::closedir;

    ######################### the "-" is really the problem here
    *CORE::GLOBAL::-d = \&Testing::MockDir::mock_d; # This does not work <<<<<
}

sub mock_d ($) {
    die 'It worked';
}

sub SetMockDir {
    my ($path, @files) = @_;
    $path2List{$path} = [@files];
}

sub UnsetMockDir {
    my ($path) = @_;
    delete $path2List{$path};
}

sub opendir (*$) {
    my $handle = qualify_to_ref(shift, caller);
    my ($path) = @_;
    return CORE::opendir($handle, $path) unless defined $path2List{$path};
    $handle2List{$handle} = $path2List{$path};
    return 1;
}

sub readdir (*) {
    my $handle = qualify_to_ref(shift, caller);
    return CORE::readdir($handle) unless defined $handle2List{$handle};
    return shift @{$handle2List{$handle}} unless wantarray;

    my @files = @{$handle2List{$handle}};
    $handle2List{$handle} = [];
    return @files;
}

sub closedir (*) {
    my $handle = qualify_to_ref(shift, caller);
    return CORE::closedir($handle) unless defined $handle2List{$handle};
    delete $handle2List{$handle};
    return 1;
}

1;

Answer 1

CORE::GLOBAL doesn't work on things without prototypes. The only way I can think to do it is rewrite the opcode tree... which is not for the faint of heart. You could pull it off with a combination of B::Utils and B::Generate and a lot of experimentation.

Simplest thing to do would be to use File::Temp to make a temporary directory structure to your liking.