NAME
Perl::Critic::Policy::ValuesAndExpressions::RequireNumericVersion - $VERSION a plain number
DESCRIPTION
This policy is part of the Perl::Critic::Pulp
add-on. It asks you to use a plain number in a module $VERSION
so that Perl's builtin version works.
Any literal number is fine, or a string which is a number,
$VERSION = 123; # ok
$VERSION = '1.5'; # ok
$VERSION = 1.200_001; # ok
For Perl 5.10 and higher the extra forms of the version
module too,
use 5.010;
$VERSION = '1.200_001'; # ok for 5.10 up, version.pm
But a non-number string is not allowed,
$VERSION = '1.2alpha'; # bad
The idea of this requirement is that a plain number is needed for Perl's builtin module version checking like the following, and on that basis this policy is under the "bugs" theme (see "POLICY THEMES" in Perl::Critic).
use Foo 1.0;
Foo->VERSION(1);
A plain number is also highly desirable so applications can do their own compares like
if (Foo->VERSION >= 1.234) {
In each case if $VERSION
is not a number then it provokes warnings, and may end up appearing as a lesser version than intended.
Argument "1.2.alpha" isn't numeric in subroutine entry
If you've loaded the version.pm
module then a $VERSION
not accepted by version.pm
will in fact croak, which is an unpleasant variant behaviour.
use version ();
print "version ",Foo->VERSION,"\n";
# croaks "Invalid version format ..." if $Foo::VERSION is bad
Scripts
This policy only looks at $VERSION
in modules. $VERSION
in a script can be anything since it won't normally be part of use
checks etc. A script $VERSION
is anything outside any package
statement scope, or under an explicit package main
.
package main;
$VERSION = '1.5.prerelease'; # ok, script
$main::VERSION = 'blah'; # ok, script
$::VERSION = 'xyzzy'; # ok, script
A fully-qualified package name is recognised as belonging to a module,
$Foo::Bar::VERSION = 'xyzzy'; # bad
Underscores in Perl 5.8 and Earlier
In Perl 5.8 and earlier a string like "1.200_333" is truncated to the numeric part, ie. 1.200, and can thus fail to satisfy
$VERSION = '1.222_333'; # bad
use Foo 1.222_331; # not satisfied by $VERSION='string' form
But an actual number literal with an "_" is allowed. Underscores in literals are stripped out (see perldata), but not in the automatic string to number conversion so a string like $VERSION = '1.222_333'
provokes a warning and stops at 1.222.
$VERSION = 1.222_333; # ok
On CPAN an underscore in a distribution version number is rated as a developer pre-release. But don't put it in module $VERSION
strings due to the problems above. The suggestion is to include the underscore in the distribution filename but either omit it from the $VERSION
or make it a number literal not a string,
$VERSION = 1.002003; # ok
$VERSION = 1.002_003; # ok, but not for VERSION_FROM
ExtUtils::MakeMaker
VERSION_FROM
will take the latter as its numeric value, ie. "1.002003" not "1.002_003" as the distribution version. For the latter you can either put an explicit VERSION
in Makefile.PL
use ExtUtils::MakeMaker;
WriteMakefile (VERSION => '1.002_003');
Or you can trick MakeMaker with a string plus eval
,
$VERSION = '1.002_003'; # ok evalled down
$VERSION = eval $VERSION;
MakeMaker
sees the string "1.002_003" but at runtime the eval
crunches it down to a plain number 1.002003. RequireNumericVersion
notices such an eval
and anything in $VERSION
. Something bizarre in $VERSION
won't be noticed, but that's too unlikely to worry about.
version
module in Perl 5.10 up
In Perl 5.10 use
etc module version checks parse $VERSION
with the version.pm
module. This policy allows the version
module forms if there's an explicit use 5.010
or higher in the file.
use 5.010;
$VERSION = '1.222_333'; # ok for 5.10
$VERSION = '1.2.3'; # ok for 5.10
But this is still undesirable, as an application check like
if (Foo->VERSION >= 1.234) {
gets the raw string from $VERSION
and thus a non-numeric warning and truncation. Perhaps applications should let UNIVERSAL.pm
do the work with say
if (eval { Foo->VERSION(1.234) }) {
or apply version->new()
to one of the args. Maybe another policy to not explicitly compare $VERSION
, or perhaps an option to tighten this policy to require numbers even in 5.10?
Exponential Format
Exponential strings like "1e6" are disallowed
$VERSION = '2.125e6'; # bad
Except with the eval
trick as per above
$VERSION = '2.125e6'; # ok
$VERSION = eval $VERSION;
Exponential number literals are fine.
$VERSION = 1e6; # ok
Exponential strings don't work in Perl 5.10 because they're not recognised by the version
module (v0.82). They're fine in Perl 5.8 and earlier, but in the interests of maximum compatibility this policy treats such a string as non-numeric. Exponentials in versions should be unusual anyway.
Disabling
If you don't care about this policy at all then you can disable from your .perlcriticrc in the usual way (see "CONFIGURATION" in Perl::Critic),
[-ValuesAndExpressions::RequireNumericVersion]
Other Ways to Do It
The version number system with underscores, multi-dots, v-nums, etc is diabolical mess, and each new addition to it just seems to make it worse. Even the original floating point in version checks is asking for rounding error trouble, though normally fine in practice. A radical simplification is to just use integer version numbers.
$VERSION = 123;
If you want sub-versions then increment by 100 or some such. Even a YYYYMMDD date is a possibility.
$VERSION = 20110328;
SEE ALSO
Perl::Critic::Pulp, Perl::Critic
Perl::Critic::Policy::Modules::RequireVersionVar, Perl::Critic::Policy::ValuesAndExpressions::ProhibitComplexVersion, Perl::Critic::Policy::ValuesAndExpressions::RequireConstantVersion
Perl::Critic::Policy::ValuesAndExpressions::ProhibitVersionStrings, Perl::Critic::Policy::Modules::ProhibitUseQuotedVersion
HOME PAGE
http://user42.tuxfamily.org/perl-critic-pulp/index.html
COPYRIGHT
Copyright 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2019, 2021 Kevin Ryde
Perl-Critic-Pulp is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.
Perl-Critic-Pulp is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with Perl-Critic-Pulp. If not, see <http://www.gnu.org/licenses/>.