CODEWITHSUNDEEP
perlmoose
Evan Carroll
Evan Carroll

Reputation: 1

Moose traits on type unions

In Moose v1.x, I used to be able to do this:

package Class;
use Test::More tests => 1;
use Moose;
use MooseX::Types::Moose qw/Undef Str/;

eval {
  has 'trait_boom' => (
    is => 'rw'
    , isa => Str | Undef
    , default => ''
    , traits => ['String']
  );
};

ok ( !$@, "Created attr trait_boom, a type union of Str and Undef\n$@" );

However, it no longer works with Moose 2.x. I assume this is a bug. Why did Moose break backwards compatibility? Is there another way to get this job done. I want that to be either Undef or a Str. I do not want to coerce Undef to an empty string though.

I'm only asking here because apparently magnet is broke

17:43 [perl2] -!- ERROR Closing Link: 64.200.109.13 (Banned)

Upvotes: 0

Views: 195

Answers (2)

perigrin
perigrin

Reputation: 4433

As we told you on MagNet right after I reported you for ban evasion, this is not a bug. The trait's methods should never have worked against the value Undef, so allowing this behavior to work in 1.x was the bug. Moose has ways optimized for correct behavior and never promised bug compat between versions.

You will either need to write your own traits or write the methods by hand to deal with this situation.

Upvotes: 2

cjm
cjm

Reputation: 62109

I would guess this was changed in Moose 2.0300, Fri, Sep 23, 2011:

  • The ->is_subtype_of and ->is_a_type_of methods have changed their behavior for union types. Previously, they returned true if any of their member types returned true for a given type. Now, all of the member types must return true. RT #67731. (Dave Rolsky)

Have you tried Maybe[Str] instead of Str | Undef?

Upvotes: 2

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