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For a long time the L<Catalyst Framework|http://catalystframework.org> has been using code attributes
to allow users to declare actions that certain URLs get dispatched to.
That looks something like this:

  lang:Perl
  sub base    : Chained('/')    PathPart('') CaptureArgs(0) { ... }
  sub index   : Chained('base') PathPart('') Args(0)        { ... }
  sub default : Chained('base') PathPart('') Args           { ... }

It's a nice and clean syntax that keeps all important information
right next to the method it belongs to.

However, attributes in perl have a couple of limitations. For one, the
interface the perl core provides to use them is horrible and doesn't
provide nearly enough information to do a lot of things, but most
importantly attributes are just plain strings. That means you will
need to parse something like C<"Chained('base')"> into
C<< (Chained => 'base') >> yourself to make proper use of them.

While that's easy for the above example, it can be very hard in the
general case because only perl can parse Perl. It's one of the reasons
you can't use L<Catalyst::Controller::ActionRole|http://search.cpan.org/perldoc?Catalyst::Controller::ActionRole> to apply
parameterized roles to your action instances, because parsing
parameters out of things like
C<< Does(SomeRole => { names => [qw/affe tiger/], answer_re => qr/42/ }) >>
would be awful and wrong.

With Catalyst 5.8 most of the attribute related code has been removed
from the internals. It's now using L<MooseX::MethodAttributes|http://search.cpan.org/perldoc?MooseX::MethodAttributes> to do
all the heavy lifting. Also the internals of how actions are
registered have been refactored to make it easier to implement
alternate ways without changing the Catalyst core.

As a proof of concept for this I implemented a new way of declaring
actions that's very similar to how L<Moose|http://search.cpan.org/perldoc?Moose> provides it's sugar
functions. You can get it from
L<github|http://github.com/rafl/catalystx-actions/tree>.

With that, the above example looks like this:

  lang:Perl
  action base    => (Chained => '/',    PathPart => '', CaptureArgs => 0) => sub { ... };
  action index   => (Chained => 'base', PathPart => '', Args    => 0    ) => sub { ... };
  action default => (Chained => 'base', PathPart => '', Args    => undef) => sub { ... };


It also moves method declaration from compiletime to runtime, making
this possible:

  lang:Perl
  for my $action (qw/foo bar baz/) {
      action $action => (Chained => 'somewhere', Args => 0) => sub {
          my ($self, $ctx) = @_;
          $ctx->stash->{ $action } = $ctx->model('Foo')->get_stuff($action);
      };
  }

Admittedly, that's all very ugly, but illustrates well what kind of
things we're able to do now. But it doesn't need to be ugly. With
L<Devel::Declare|http://search.cpan.org/perldoc?Devel::Declare> we have a great tool to add our own awesome syntax
to perl, similar to how things like L<MooseX::Method::Signatures|http://search.cpan.org/perldoc?MooseX::Method::Signatures>,
L<MooseX::MultiMethods|http://search.cpan.org/perldoc?MooseX::MultiMethods> and L<MooseX::Declare|http://search.cpan.org/perldoc?MooseX::Declare> do.

So how would a declarative syntax for Catalyst controllers look like?
I don't know. Ideas include something like this:

  under /some/where, action foo ('foo', $id) { ... }

to mean:

  sub foo : Chained('/some/where') PathPart('foo') CaptureArgs(1) { ... }

Adding Moose type constraints to this would be interesting, too, and
make validation of captures and arguments a lot easier. Multi dispatch
similar to MooseX::MultiMethods could be handy as well:

  under /some/where {
      action ('foo', Int $id) {
          # find and stash an item by id
      }
      action ('foo', Str $name) {
          # search items using $name
      }
      action ('foo', Any $thing) {
          # display error page
      }
  }

So you see there are a lot of possibilities that should be
explored. Unfortunately I have no idea what kind of syntax and
features people would like to have, so your feedback on this would be
much appreciated. :-)

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