Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl-Sensitive Sunglasses
 
PerlMonks  

Re: Perl::Critic error "Readonly version 21 required"

by tobyink (Abbot)
on Feb 15, 2013 at 06:53 UTC ( #1018850=note: print w/ replies, xml ) Need Help??


in reply to Perl::Critic error "Readonly version 21 required"

Note:

0x15 == 21
package Cow { use Moo; has name => (is => 'lazy', default => sub { 'Mooington' }) } say Cow->new->name


Comment on Re: Perl::Critic error "Readonly version 21 required"
Download Code
Re^2: Perl::Critic error "Readonly version 21 required"
by tobyink (Abbot) on Feb 15, 2013 at 10:06 UTC

    It seems Exporter (which Readonly, and many, many, many, many other modules use internally) has a weird feature (in my opinion a misfeature) where it does its own module version number checking.

    Normally when you write:

    use Module 1.23;

    ... perl will catch the version number, and not treat it as an argument to Module->import, instead passing it to Module->VERSION to act as a version number check.

    However, it seems Exporter makes an attempt to catch number-like arguments that perl has missed, and do its own version checking with them. Notice the difference between the following two examples; the first one where the version check is done by perl, and the second where it's done by Exporter.pm

    $ perl -e'use Carp 100 ()' Carp version 100 required--this is only version 1.26 at -e line 1. BEGIN failed--compilation aborted at -e line 1. $ perl -e'use Carp () => 100' Carp version 100 required--this is only version 1.26 at /home/tai/perl +5/perlbrew/perls/perl-5.16.2/lib/5.16.2/Exporter/Heavy.pm line 120. BEGIN failed--compilation aborted at -e line 1.

    In your original example, this line:

    use Readonly my $unprintable => 0x15;

    ... is run as:

    use Readonly undef => 0x15;

    ... because the variable is undefined. So Exporter's version number check kicks in, even though the 0x15 was clearly never intended as a module version number.

    Yet another reason to avoid using Exporter and use something sane like Sub::Exporter.

    package Cow { use Moo; has name => (is => 'lazy', default => sub { 'Mooington' }) } say Cow->new->name
      Sheesh. I had no idea what your previous post meant. Thanks for the explanation.

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://1018850]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others meditating upon the Monastery: (11)
As of 2015-07-03 13:11 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (53 votes), past polls