I'm not sure how to solve your problem, explanation wise, however I might 
wonder if we can find a way to use a role, either Moose or Moo, instead of a 
class for your plugin.  I find its a more sane implementation.  I know a lot of 
legacy stuff from pre Catamoose doesn't do that but I can't think of a good 
reason why we'd not wish for them to all be converted.  Basically what I think 
of a plugin in Catalyst is just a role but we didn't have roles at the time 
Catalyst was first done so we were stuck rolling our own.  There's a few other 
weird things like how plugins are applied at setup_plugin time rather than 
earlier (which again I personally find to be a real pain in the butt but maybe 
there's some actually good use for it, just I don't see it.)


Even the role interface is probably too much since its applied on top of the 
application (and then automatically on the context).  Its a big hammer.  Then 
number one thing that always stopped me from bigger Catalyst refactoring is 
that I have not idea what people did to Catalyst internals with plugins... Its 
hard to figure out what you are breaking, which is why I tended to encourage 
people to try and use other things when they could like custom models, 
middleware, etc.  But you still need them from time to time I guess.   If all 
you want is some application scoped attributes you could do that with a 
application model, for example.  I personally consider 
'MooseX::Emulate::Class::Accessor::Fast' something that was written as an 
expedient way to get get CataMoose off the ground. I definitely would not use 
it in my code, particularly if I could use Moose or Moo anyway.  I wasn't 
around for most of CataMoose so I don't know the reasons why a lot of stuff was 
done in certain ways, but tho
 se shims I'd not use for new stuff.  I always assumed it was 'until someone 
has time to fix this right' but then no body bothered.

Sorry this probably didn't help.  snap


On Sunday, November 22, 2015 3:03 PM, Bill Moseley <mose...@hank.org> wrote:



I wanted to note something (before the week gets started and time vanishes) 
about how Catalyst is behaving, and see if it's expected.

I asked about this on the Moose list, so sorry if you already saw this.

A Catalyst app extends Catalyst::Component, which has a BUILDARGS sub to merge 
in class configuration when creating instances of components.

This is how configuration can set initial values on attributes in Models, 
Views, Controllers, and the application class itself. 

If a (non-role) Moose-based plugin is loaded (which is common) it's added to 
the app's inheritance like this:

$meta->superclasses($plugin, $meta->superclasses);

 Which can be thought of like this:

@App::ISA = ( qw/ Catalyst::Plugin::Foo  Catalyst / );

The result then is that BUILDARGS in Catalyst::Component is no longer called, 
and then attributes in the App class are no longer populated from the config.

So, the behavior changes depending on what plugins are brought in.

Another odd issue I came against is that MooseX::Emulate::Class::Accessor::Fast 
causes odd behavior of Moose attributes.   This role is widely used in Catalyst.

In the code below note how the "foo" attribute has init_arg => undef to prevent 
it from being initialized.  With the the role not only is it initialized, but 
with a value that isn't an "Int".



package Foo;
>use Moose;
>
>
>with 'MooseX::Emulate::Class::Accessor::Fast';
>
>has foo => (
>    is  => 'ro',
>    isa => 'Int', # for error
>    init_arg => undef,
>);
>
>
>
>package main;
>use strict;
>use warnings;
>
>
>my $foo = Foo->new( { foo => 'bar' } );
>
>
>use Data::Dumper;
>print Dumper $foo->foo;


Generates 'bar', which is not an Int.

$VAR1 = 'bar';


Comment out "with 'MooseX::Emulate::Class::Accessor::Fast';" and it behaves as 
expected.   Also comment out "init_arg" and Moose will complain about the 
string not begin an Int.

-- 

Bill Moseley
mose...@hank.org
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