Question

I realise that this is not generally possible for all MooseX modules, particularly where the module delves into the meta class where Moose and Mouse differ.

But this question arose because sometimes a MooseX module doesn’t have an equivalent in the MouseX namespace, and I found that I could still use the MooseX module within my Mouse classes. But I want to ask this question in general, even if there is a MouseX equivalent available (let’s say I’m too lazy to install the MouseX one, or the MooseX version is more recent with new features).

For example, the following is valid:

package Foo;
use Mouse;
use MooseX::Types::Common::Numeric 'PositiveInt';
has 'bar' => (
    is => 'rw',
    isa => PositiveInt,
);

When I looked into MouseX::Types::Common::Numeric source it was almost an exact copy of MooseX::Types::Common::Numeric, though there were differences in MouseX::Types which is a dependency. Since it is perl code there is no particular performance benefit in using the MouseX module either.

So if we have a Mouse class and a choice of using equivalent MooseX and MouseX modules, what reasons would we have to choose the MouseX option? Why have the MouseX equivalent anyway?

btw, how should we relate to this with Any::Moose?

Answer 1

The point of using Mouse is to have access to most features of Moose while eliminating its expensive startup time and Yggdrasil-like dependency tree. If you’re using a MooseX module with it, that module brings in Moose, or at least Moose::Exporter/Moose::Role, and you’ve then eliminated the benefits of Mouse. Observe:

rsimoes@desk-o-simoes:~$ time perl -MMouse -e 1

real    0m0.026s
user    0m0.020s
sys     0m0.000s

rsimoes@desk-o-simoes:~$ time perl -MMouse -MMouseX::Types::Common::Numeric -e 1

real    0m0.032s
user    0m0.030s
sys     0m0.000s

So fast! But then:

rsimoes@desk-o-simoes:~$ time perl -MMoose -e 1

real    0m0.148s
user    0m0.120s
sys     0m0.020s

rsimoes@desk-o-simoes:~$ time perl -MMouse -MMooseX::Types::Common::Numeric -e 1

real    0m0.181s
user    0m0.150s
sys     0m0.020s

So slow. But if those startup times don’t matter for what you’re doing, You shouldn’t even be bothering with Mouse to begin with.

Any::Moose exists to allow a Moose-oriented module to use Mouse unless Moose is already loaded, in which case it’ll just use that.