Regexp::Pattern - Convention/framework for modules that contain collection of regexes
0.2
This document describes version 0.2.14 of Regexp::Pattern (from Perl distribution Regexp-Pattern), released on 2020-04-01.
Subroutine interface:
use Regexp::Pattern; # exports re()
my $re = re('YouTube::video_id');
say "ID does not look like a YouTube video ID" unless $id =~ /\A$re\z/;
# a dynamic pattern (generated on-demand) with generator arguments
my $re2 = re('Example::re3', {variant=>"B"});
Hash interface (a la the Regexp::Common manpage but simpler with regular/non-magical hash
that is only 1-level deep):
use Regexp::Pattern 'YouTube::video_id';
say "ID does not look like a YouTube video ID"
unless $id =~ /\A$RE{video_id}\z/;
# more complex example
use Regexp::Pattern (
're', # we still want the re() function
'Foo::bar' => (-as => 'qux'), # the pattern will be in your $RE{qux}
'YouTube::*', # wildcard import
'Example::re3' => (variant => 'B'), # supply generator arguments
'JSON::*' => (-prefix => 'json_'), # add prefix
'License::*' => (
# filtering options
-has_tag => 'family:cc', # only select patterns that have this tag
-lacks_tag => 'type:unversioned', # only select patterns that do not have this tag
-has_tag_matching => qr/^type:/, # only select patterns that have at least a tag matching this regex
-lacks_tag_matching => qr/^type:/, # only select patterns that do not have any tags matching this regex
# other options
-prefix => 'pat_', # add prefix
-suffix => '_license', # add suffix
),
);
Regexp::Pattern is a convention for organizing reusable regexp patterns in
modules, as well as framework to provide convenience in using those patterns in
your program.
package Regexp::Pattern::Example;
our %RE = (
# the minimum spec
re1 => { pat => qr/\d{3}-\d{3}/ },
# more complete spec
re2 => {
summary => 'This is regexp for blah', # plaintext
description => <<'_',
A longer description in *Markdown* format.
_
pat => qr/\d{3}-\d{3}(?:-\d{5})?/,
tags => ['A','B'],
examples => [
# examples can be tested using 'test-regexp-pattern' script
# (distributed in Test-Regexp-Pattern distribution). examples can
# also be rendered in your POD using
# Pod::Weaver::Plugin::Regexp::Pattern.
{
str => '123-456',
matches => 1,
},
{
summary => 'Another example that matches',
str => '123-456-78901',
matches => 1,
},
{
summary => 'An example that does not match',
str => '123456',
matches => 0,
},
{
summary => 'An example that does not get tested',
str => '123456',
},
{
summary => 'Another example that does not get tested nor rendered to POD',
str => '234567',
matches => 0,
test => 0,
doc => 0,
},
],
},
# dynamic (regexp generator)
re3 => {
summary => 'This is a regexp for blah blah',
description => <<'_',
...
_
gen => sub {
my %args = @_;
my $variant = $args{variant} || 'A';
if ($variant eq 'A') {
return qr/\d{3}-\d{3}/;
} else { # B
return qr/\d{3}-\d{2}-\d{5}/;
}
},
gen_args => {
variant => {
summary => 'Choose variant',
schema => ['str*', in=>['A','B']],
default => 'A',
req => 1,
},
},
tags => ['B','C'],
examples => [
{
summary => 'An example that matches',
gen_args => {variant=>'A'},
str => '123-456',
matches => 1,
},
{
summary => "An example that doesn't match",
gen_args => {variant=>'B'},
str => '123-456',
matches => 0,
},
],
},
re4 => {
summary => 'This is a regexp that does capturing',
# it is recommended that your pattern does not capture, unless
# necessary. capturing pattern should tag with 'capturing' to let
# users/tools know.
tags => ['capturing'],
pat => qr/(\d{3})-(\d{3})/,
examples => [
{str=>'123-456', matches=>[123, 456]},
{str=>'foo-bar', matches=>[]},
],
},
re5 => {
summary => 'This is another regexp that is anchored and does (named) capturing',
# it is recommended that your pattern is not anchored for more
# reusability, unless necessary. anchored pattern should tag with
# 'anchored' to let users/tools know.
tags => ['capturing', 'anchored'],
pat => qr/^(?<cap1>\d{3})-(?<cap2>\d{3})/,
examples => [
{str=>'123-456', matches=>{cap1=>123, cap2=>456}},
{str=>'something 123-456', matches=>{}},
],
},
);
A Regexp::Pattern::* module must declare a package global hash variable named
%RE. Hash keys are pattern names, hash values are pattern definitions in the
form of defhashes (see DefHash).
Pattern name should be a simple identifier that matches this regexp: <
/\A[A-Za-z_][A-Za-z_0-9]*\z/ >. The definition for the qualified pattern name
Foo::Bar::baz can then be located in %Regexp::Pattern::Foo::Bar::RE under
the hash key baz.
Pattern definition hash should at the minimum be:
{ pat => qr/.../ }
You can add more stuffs from the defhash specification, e.g. summary,
description, tags, and so on, for example (taken from the Regexp::Pattern::CPAN manpage):
{
summary => 'PAUSE author ID, or PAUSE ID for short',
pat => qr/[A-Z][A-Z0-9]{1,8}/,
description => <<~HERE,
I'm not sure whether PAUSE allows digit for the first letter. For safety
I'm assuming no.
HERE
examples => [
{str=>'PERLANCAR', matches=>1},
{str=>'BAD ID', anchor=>1, matches=>0},
],
}
Examples. Your regexp specification can include an examples property (see
above for example). The value of the examples property is an array, each of
which should be a defhash. For each example, at the minimum you should specify
str (string to be matched by the regexp), gen_args (hash, arguments to use
when generating dynamic regexp pattern), and matches (a boolean value that
specifies whether the regexp should match the string or not, or an array/hash
that specifies the captures). You can of course specify other defhash properties
(e.g. summary, description, etc). Other example properties might be
introduced in the future.
If you use the Dist::Zilla manpage to build your distribution, you can use the plugin
[Regexp::Pattern] to test the examples
during building, and the the Pod::Weaver manpage plugin
[-Regexp::Pattern] to render the
examples in your POD.
A Regexp::Pattern::* module can be used in a standalone way (i.e. no need to use
via the Regexp::Pattern framework), as it simply contains data that can be
grabbed using a normal means, e.g.:
use Regexp::Pattern::Example;
say "Input does not match blah"
unless $input =~ /\A$Regexp::Pattern::Example::RE{re1}{pat}\z/;
Regexp::Pattern (this module) also provides re() function to help retrieve
the regexp pattern. See re for more details.
Additionally, Regexp::Pattern (since v0.2.0) lets you import regexp patterns
into your %RE package hash variable, a la the Regexp::Common manpage (but simpler
because the hash is just a regular hash, only 1-level deep, and not magical).
To import, you specify qualified pattern names as the import arguments:
use Regexp::Pattern 'Q::pat1', 'Q::pat2', ...;
Each qualified pattern name can optionally be followed by a list of name-value
pairs. A pair name can be an option name (which is dash followed by a word, e.g.
-as, -prefix) or a generator argument name for dynamic pattern.
Wildcard import. Instead of a qualified pattern name, you can use
'Module::SubModule::*' wildcard syntax to import all patterns from a pattern
module.
Importing into a different name. You can add the import option -as to
import into a different name, for example:
use Regexp::Pattern 'YouTube::video_id' => (-as => 'yt_id');
Prefix and suffix. You can also add a prefix and/or suffix to the imported
name:
use Regexp::Pattern 'Example::*' => (-prefix => 'example_');
use Regexp::Pattern 'Example::*' => (-suffix => '_sample');
Filtering. When wildcard-importing, you can select the patterns you want
using a combination of these options: -has_tag (only select patterns that
have a specified tag), -lacks_tag (only select patterns that do not have a
specified tag), -has_tag_matching (only select patterns that have at least
one tag matching specified regex pattern), -lacks_tag_matching (only select
patterns that do not have any tags matching specified regex pattern).
- Regexp pattern should in general be written as a qr// literal instead of string
That is:
pat => qr/foo[abc]+/,
is preferred over:
pat => 'foo[abc]+',
Using a string literal is less desirable because of lack of compile-time
checking. An exception to this rule is when you want to delay regex compilation
for some reason, e.g. you want your user to compile the patterns themselves
using different regex engine (see re::engine::* modules on CPAN).
- Regexp pattern should not be anchored (unless really necessary)
That is:
pat => qr/foo/,
is preferred over:
pat => qr/^foo/, # or qr/foo$/, or qr/\Afoo\z/
Adding anchors limits the reusability of the pattern. When composing pattern,
user can add anchors herself if needed.
When you define an anchored pattern, adding tag anchored is recommended:
tags => ['anchored'],
- Regexp pattern should not contain capture groups (unless really necessary)
Adding capture groups limits the reusability of the pattern because it can
affect the groups of the composed pattern. When composing pattern, user can add
captures herself if needed.
When you define a capturing pattern, adding tag capturing is recommended:
tags => ['capturing'],
Exported by default. Get a regexp pattern by name from a Regexp::Pattern::*
module.
Usage:
re($name[, \%args ]) => $re
$name is MODULE_NAME::PATTERN_NAME where MODULE_NAME is name of a
Regexp::Pattern::* module without the Regexp::Pattern:: prefix and
PATTERN_NAME is a key to the %RE package global hash in the module. A
dynamic pattern can accept arguments for its generator, and you can pass it as
hashref in the second argument of re().
Anchoring. You can also put -anchor => 1 in %args. This will
conveniently wraps the regex inside qr/\A(?:...)\z/. To only add left
anchoring, specify -anchor => 'left' (qr/\A(?:...)/. To only add
right anchoring, specify -anchor => 'right' (qr/(?:...)\z/.
Die when pattern by name $name cannot be found (either the module cannot be
loaded or the pattern with that name is not found in the module).
You can add anchor=>1 or gen_args=>{-anchor=>1} in the example,
for example:
{
summary => 'PAUSE author ID, or PAUSE ID for short',
pat => qr/[A-Z][A-Z0-9]{1,8}/,
description => <<~HERE,
I'm not sure whether PAUSE allows digit for the first letter. For safety
I'm assuming no.
HERE
examples => [
{str=>'PERLANCAR', matches=>1},
{str=>'BAD ID', anchor=>1, matches=>0, summary=>"Contains whitespace"},
{str=>'NAMETOOLONG', gen_args=>{-anchor=>1}, matches=>0, summary=>"Too long"},
],
}
Please visit the project's homepage at https://metacpan.org/release/Regexp-Pattern.
Source repository is at https://github.com/perlancar/perl-Regexp-Pattern.
Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Regexp-Pattern
When submitting a bug or request, please include a test-file or a
patch to an existing test-file that illustrates the bug or desired
feature.
the Regexp::Common manpage. Regexp::Pattern is an alternative to Regexp::Common.
Regexp::Pattern offers simplicity and lower startup overhead. Instead of a magic
hash, you retrieve available regexes from normal data structure or via the
provided re() function. Regexp::Pattern also provides a hash interface,
albeit the hash is not magic.
the Regexp::Common::RegexpPattern manpage, a bridge module to use patterns in
Regexp::Pattern::* modules via Regexp::Common.
the Regexp::Pattern::RegexpCommon manpage, a bridge module to use patterns in
Regexp::Common::* modules via Regexp::Pattern.
the App::RegexpPatternUtils manpage
If you use the Dist::Zilla manpage: the Dist::Zilla::Plugin::Regexp::Pattern manpage,
the Pod::Weaver::Plugin::Regexp::Pattern manpage,
the Dist::Zilla::Plugin::AddModule::RegexpCommon::FromRegexpPattern manpage,
the Dist::Zilla::Plugin::AddModule::RegexpPattern::FromRegexpCommon manpage.
the Test::Regexp::Pattern manpage and test-regexp-pattern.
perlancar <perlancar@cpan.org>
This software is copyright (c) 2020, 2019, 2018, 2016 by perlancar@cpan.org.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
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