Add the OutputCache plugin, which stores the most recent result in _

git-svn-id: http://dev.catalyst.perl.org/repos/bast/trunk/Devel-REPL@3895 bd8105ee-0ff8-0310-8827-fb3f25b6796d

diff --git a/lib/Devel/REPL/Plugin/OutputCache.pm b/lib/Devel/REPL/Plugin/OutputCache.pm
new file mode 100644 (file)
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--- /dev/null
+++ b/lib/Devel/REPL/Plugin/OutputCache.pm
@@ -0,0 +1,104 @@
+package Devel::REPL::Plugin::OutputCache;
+
+use Moose::Role;
+use namespace::clean -except => [ 'meta' ];
+
+has output_cache => (
+    is      => 'rw',
+    isa     => 'ArrayRef',
+    default => sub { [] },
+    lazy    => 1,
+);
+
+around 'eval' => sub {
+    my $orig = shift;
+    my ($self, $line) = @_;
+
+    local *_ = sub () { $self->output_cache->[-1] };
+
+    my @ret;
+    if (wantarray) {
+        @ret = $self->$orig($line);
+    }
+    else {
+        $ret[0] = $self->$orig($line);
+    }
+
+    push @{ $self->output_cache }, @ret > 1 ? \@ret : $ret[0];
+    return wantarray ? @ret : $ret[0];
+};
+
+1;
+
+__END__
+
+=head1 NAME
+
+Devel::REPL::Plugin::OutputCache - remember past results, _ is most recent
+
+=head1 SYNOPSIS
+
+    > 21 / 7
+    3
+    > _ * _
+    9
+    > sub { die "later" }
+    sub { die "later" }
+    > _->()
+    Runtime error: later
+
+=head1 DESCRIPTION
+
+Re-using results is very useful when working in a REPL. With C<OutputCache> you
+get C<_>, which holds the past result. The benefit is that you can build up
+your result instead of having to type it in all at once, or store it in
+intermediate variables. C<OutputCache> also provides
+C<< $_REPL->output_cache >>, an array reference of all results in this session.
+
+Devel::REPL already has a similar plugin, L<Devel::REPL::Plugin::History>.
+There are some key differences though:
+
+=over 4
+
+=item Input vs Output
+
+C<History> remembers input. C<OutputCache> remembers output.
+
+=item Munging vs Pure Perl
+
+C<History> performs regular expressions on your input. C<OutputCache> provides
+the C<_> sub as a hook to get the most recent result, and
+C<< $_REPL->output_cache >> for any other results.
+
+=item Principle of Least Surprise
+
+C<History> will replace exclamation points in any part of the input. This is
+problematic if you accidentally include one in a string, or in a C<not>
+expression. C<OutputCache> uses a regular (if oddly named) subroutine so Perl
+does the parsing -- no surprises.
+
+=back
+
+=head1 CAVEATS
+
+The C<_> sub is shared across all packages. This means that if a module is
+using the C<_> sub, then there is a conflict and you should not use this
+plugin. For example, L<Jifty> uses the C<_> sub for localization. Jifty is the
+only known user.
+
+=head1 SEE ALSO
+
+C<Devel::REPL>, C<Devel::REPL::Plugin::History>
+
+=head1 AUTHOR
+
+Shawn M Moore, C<< <sartak at gmail dot com> >>
+
+=head1 COPYRIGHT AND LICENSE
+
+Copyright (C) 2007 by Shawn M Moore
+
+This library is free software; you can redistribute it and/or modify
+it under the same terms as Perl itself.
+
+=cut