On Sat, 4 Oct 2014, Karen Etheridge wrote:
On Fri, Oct 03, 2014 at 09:28:22PM +0000, John Macdonald wrote:
If you have a role and its consumer both specify the same attribute name
(neither one using +name) there is no complaint from Moose and the second one
encountered is used and the first is ignored.
I tracked this down after getting an error that the predicate method was not
found - that was defined in the version of the attribute that was discarded
without notice.
Could there be something done in the 'has' handler to detect such duplicates
and give an error rather than this sort of quiet misaction?
This is actually a feature. Roles and subclasses should be able to
completely override an earlier attribute declaration. There are, of
course, opportunities to make this more clear in documentation...
should be able to != do it silently
I think there's an opportunity to do both here, by bringing Attribute
consumption more in line with Method consumption by making conflict resolution
explicit. Making Attributes entirely Private to both Classes and Roles ala
p5-mop-redux would be ideal, but if Moose Roles are aiming to become Trait
compliant, we really need to take this 'order of Role consumption' issue out of
the equation, and that requires explicit conflict resolution.
As Ovid observed last year in the 2.0800 announcement thread, with virtually no
response from the list, is that this order of consumption 'feature' goes
against the very core of what Traits are and how very deliberately this
solution was chosen.
I've not contributed a line of code yet, and a large reason was last year's
silence on this topic. I'd be much more excited about contributing and helping
implement this stuff if Moose was looking to become Trait compliant, but if
it's not then it won't pay off the type of returns that are possible with
Traits and I have a hard time justifying the investment in time.
No offense, IMHO etc. - just hoping that people think about this if not discuss
it publicly here on the list :-) Cheers,
--
Niall Young
ni...@iinet.net.au
