initial commit

2 files changed, 85 insertions, 0 deletions

diff --git a/lib/MooseX/ABC.pm b/lib/MooseX/ABC.pm
new file mode 100644
index 0000000..f0f1412
--- /dev/null
+++ b/lib/MooseX/ABC.pm
@@ -0,0 +1,54 @@
+package MooseX::ABC;
+use Moose ();
+use Moose::Exporter;
+use Moose::Util::MetaRole;
+
+sub requires {
+    my $caller = shift;
+    my $meta = Class::MOP::class_of($caller);
+    $meta->add_required_method($_) for @_;
+}
+
+Moose::Exporter->setup_import_methods(
+    with_caller => [qw(requires)],
+);
+
+sub init_meta {
+    shift;
+    my %options = @_;
+    Moose->init_meta(%options);
+    Moose::Util::MetaRole::apply_metaclass_roles(
+        for_class       => $options{for_class},
+        metaclass_roles => ['MooseX::ABC::Trait::Class'],
+    );
+    return Class::MOP::class_of($options{for_class});
+}
+
+=for motivation
+
+22:41 <@rjbs> So, say I wanted to write 'shape'
+22:41 <@rjbs> as a class
+22:41 <@rjbs> but an abstract base class
+22:41 <@rjbs> I could say: requires 'area'
+22:41 <@rjbs> except I can't, because a class can't be abstract in that sense,
+              in Perl
+22:41 <@rjbs> er, in Moose
+22:42 <@rjbs> so to use a delegate is a compromise
+22:42 <@rjbs> It isn't what I want: an ABC
+22:42 <@rjbs> It isn't entirely what I don't wnat: a role
+22:42 <@doy> i wonder if something like a lazy role would work
+22:42 <@rjbs> lazy role?
+22:42 <@doy> instead of dying if all required methods aren't satisfied at
+             compile time, do it at instantiation time
+22:43 <@doy> applying a role and not satisfying all requires turns that class
+             into an abstract class
+22:43 <@rjbs> but now we're back to instantiation time!
+22:43 <@rjbs> I want compile time.
+22:44 <@rjbs> package Shape; use Moose::ABC; # now you get no new method, you
+              can't instantiate directly, and you have "requires" sugar
+22:44 <@rjbs> and if you "extends 'Shape'" without fulfilling rqeuires, you die
+22:44 <@doy> yeah, that would be nicer
+
+=cut
+
+1;
diff --git a/lib/MooseX/ABC/Trait/Class.pm b/lib/MooseX/ABC/Trait/Class.pm
new file mode 100644
index 0000000..c8b7341
--- /dev/null
+++ b/lib/MooseX/ABC/Trait/Class.pm
@@ -0,0 +1,31 @@
+package MooseX::ABC::Trait::Class;
+use Moose::Role;
+use MooseX::AttributeHelpers;
+
+has required_methods => (
+    metaclass => 'Collection::Array',
+    is        => 'ro',
+    isa       => 'ArrayRef[Str]',
+    default   => sub { [] },
+    provides  => {
+        push => 'add_required_method',
+    },
+);
+
+after _superclasses_updated => sub {
+    my $self = shift;
+    for my $superclass ($self->linearized_isa) {
+        my $super_meta = Class::MOP::class_of($superclass);
+        next unless $super_meta->does_role('MooseX::ABC::Trait::Class');
+        for my $method ($super_meta->required_methods) {
+            if (!$self->find_method_by_name($method)) {
+                my $classname = $self->name;
+                die "$superclass requires $classname to implement $method";
+            }
+        }
+    }
+};
+
+no Moose::Role;
+
+1;