(OK, the subject sucked, but I tried :)
From S14:
You can, however, say
$fido does Sentry;
$fido does Tricks;
$fido does TailChasing;
$fido does Scratch;
<snip>
Unlike the compile-time role composition, each of these layers
on a new mixin with a new level of inheritance, creating a new
anonymous class for dear old Fido, so that a .chase method from
TailChasing hides a .chase method from Sentry.
Recently I reported a bug in Moose's runtime role application:
http://rt.cpan.org/Public/Bug/Display.html?id=43904
The problem was very hard to track down because I was effectively doing
something like this:
$object->meta->apply('Some::Role') while 1;
(The reality is that we had a singleton with a role applied to it multiple
times).
Eventually, the code broke and threw a bunch of weird "recursive inheritance"
warnings due to multiple anonymous classes being applied to the object. This
was *real fun* to debug, but I can imagine a scenario for this being natural:
Your REST interface returns XML, but sometimes someone wants YAML. So you have:
$resultset does Role::Serializable::XML
But sometimes:
$resultset does Role::Serializable::YAML
Since you cache resultsets if they've not changed, you could easily have the
XML and YAML roles getting reapplied at runtime multiple times.
I don't see anything in the spec addressing this. Aside from "don't do that",
is this something which can be addressed in perl instead of Perl?
Cheers,
Ovid
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