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CPAN::Meta::Spec(3perl) Perl Programmers Reference Guide CPAN::Meta::Spec(3perl)
NAME
CPAN::Meta::Spec - specification for CPAN distribution metadata
VERSION
version 2.150010
SYNOPSIS
my $distmeta = {
name => 'Module-Build',
abstract => 'Build and install Perl modules',
description => "Module::Build is a system for "
. "building, testing, and installing Perl modules. "
. "It is meant to ... blah blah blah ...",
version => '0.36',
release_status => 'stable',
author => [
'Ken Williams <kwilliams AT cpan.org>',
'Module-Build List <module-build AT perl.org>', # additional contact
],
license => [ 'perl_5' ],
prereqs => {
runtime => {
requires => {
'perl' => '5.006',
'ExtUtils::Install' => '0',
'File::Basename' => '0',
'File::Compare' => '0',
'IO::File' => '0',
},
recommends => {
'Archive::Tar' => '1.00',
'ExtUtils::Install' => '0.3',
'ExtUtils::ParseXS' => '2.02',
},
},
build => {
requires => {
'Test::More' => '0',
},
}
},
resources => {
license => ['http://dev.perl.org/licenses/'],
},
optional_features => {
domination => {
description => 'Take over the world',
prereqs => {
develop => { requires => { 'Genius::Evil' => '1.234' } },
runtime => { requires => { 'Machine::Weather' => '2.0' } },
},
},
},
dynamic_config => 1,
keywords => [ qw/ toolchain cpan dual-life / ],
'meta-spec' => {
version => '2',
url => 'https://metacpan.org/pod/CPAN::Meta::Spec',
},
generated_by => 'Module::Build version 0.36',
};
DESCRIPTION
This document describes version 2 of the CPAN distribution metadata specification, also
known as the "CPAN Meta Spec".
Revisions of this specification for typo corrections and prose clarifications may be
issued as CPAN::Meta::Spec 2.x. These revisions will never change semantics or add or
remove specified behavior.
Distribution metadata describe important properties of Perl distributions. Distribution
building tools like Module::Build, Module::Install, ExtUtils::MakeMaker or Dist::Zilla
should create a metadata file in accordance with this specification and include it with
the distribution for use by automated tools that index, examine, package or install Perl
distributions.
TERMINOLOGY
distribution
This is the primary object described by the metadata. In the context of this document
it usually refers to a collection of modules, scripts, and/or documents that are
distributed together for other developers to use. Examples of distributions are
"Class-Container", "libwww-perl", or "DBI".
module
This refers to a reusable library of code contained in a single file. Modules usually
contain one or more packages and are often referred to by the name of a primary
package that can be mapped to the file name. For example, one might refer to
"File::Spec" instead of File/Spec.pm
package
This refers to a namespace declared with the Perl "package" statement. In Perl,
packages often have a version number property given by the $VERSION variable in the
namespace.
consumer
This refers to code that reads a metadata file, deserializes it into a data structure
in memory, or interprets a data structure of metadata elements.
producer
This refers to code that constructs a metadata data structure, serializes into a
bytestream and/or writes it to disk.
must, should, may, etc.
These terms are interpreted as described in IETF RFC 2119.
DATA TYPES
Fields in the "STRUCTURE" section describe data elements, each of which has an associated
data type as described herein. There are four primitive types: Boolean, String, List and
Map. Other types are subtypes of primitives and define compound data structures or define
constraints on the values of a data element.
Boolean
A Boolean is used to provide a true or false value. It must be represented as a defined
value that is either "1" or "0" or stringifies to those values.
String
A String is data element containing a non-zero length sequence of Unicode characters, such
as an ordinary Perl scalar that is not a reference.
List
A List is an ordered collection of zero or more data elements. Elements of a List may be
of mixed types.
Producers must represent List elements using a data structure which unambiguously
indicates that multiple values are possible, such as a reference to a Perl array (an
"arrayref").
Consumers expecting a List must consider a String as equivalent to a List of length 1.
Map
A Map is an unordered collection of zero or more data elements ("values"), indexed by
associated String elements ("keys"). The Map's value elements may be of mixed types.
License String
A License String is a subtype of String with a restricted set of values. Valid values are
described in detail in the description of the "license" field.
URL
URL is a subtype of String containing a Uniform Resource Locator or Identifier. [ This
type is called URL and not URI for historical reasons. ]
Version
A Version is a subtype of String containing a value that describes the version number of
packages or distributions. Restrictions on format are described in detail in the "Version
Formats" section.
Version Range
The Version Range type is a subtype of String. It describes a range of Versions that may
be present or installed to fulfill prerequisites. It is specified in detail in the
"Version Ranges" section.
STRUCTURE
The metadata structure is a data element of type Map. This section describes valid keys
within the Map.
Any keys not described in this specification document (whether top-level or within
compound data structures described herein) are considered custom keys and must begin with
an "x" or "X" and be followed by an underscore; i.e. they must match the pattern:
"qr{\Ax_}i". If a custom key refers to a compound data structure, subkeys within it do
not need an "x_" or "X_" prefix.
Consumers of metadata may ignore any or all custom keys. All other keys not described
herein are invalid and should be ignored by consumers. Producers must not generate or
output invalid keys.
For each key, an example is provided followed by a description. The description begins
with the version of spec in which the key was added or in which the definition was
modified, whether the key is required or optional and the data type of the corresponding
data element. These items are in parentheses, brackets and braces, respectively.
If a data type is a Map or Map subtype, valid subkeys will be described as well.
Some fields are marked Deprecated. These are shown for historical context and must not be
produced in or consumed from any metadata structure of version 2 or higher.
REQUIRED FIELDS
abstract
Example:
abstract => 'Build and install Perl modules'
(Spec 1.2) [required] {String}
This is a short description of the purpose of the distribution.
author
Example:
author => [ 'Ken Williams <kwilliams AT cpan.org>' ]
(Spec 1.2) [required] {List of one or more Strings}
This List indicates the person(s) to contact concerning the distribution. The preferred
form of the contact string is:
contact-name <email-address>
This field provides a general contact list independent of other structured fields provided
within the "resources" field, such as "bugtracker". The addressee(s) can be contacted for
any purpose including but not limited to (security) problems with the distribution,
questions about the distribution or bugs in the distribution.
A distribution's original author is usually the contact listed within this field. Co-
maintainers, successor maintainers or mailing lists devoted to the distribution may also
be listed in addition to or instead of the original author.
dynamic_config
Example:
dynamic_config => 1
(Spec 2) [required] {Boolean}
A boolean flag indicating whether a Build.PL or Makefile.PL (or similar) must be executed
to determine prerequisites.
This field should be set to a true value if the distribution performs some dynamic
configuration (asking questions, sensing the environment, etc.) as part of its
configuration. This field should be set to a false value to indicate that prerequisites
included in metadata may be considered final and valid for static analysis.
Note: when this field is true, post-configuration prerequisites are not guaranteed to bear
any relation whatsoever to those stated in the metadata, and relying on them doing so is
an error. See also "Prerequisites for dynamically configured distributions" in the
implementors' notes.
This field explicitly does not indicate whether installation may be safely performed
without using a Makefile or Build file, as there may be special files to install or custom
installation targets (e.g. for dual-life modules that exist on CPAN as well as in the Perl
core). This field only defines whether or not prerequisites are exactly as given in the
metadata.
generated_by
Example:
generated_by => 'Module::Build version 0.36'
(Spec 1.0) [required] {String}
This field indicates the tool that was used to create this metadata. There are no defined
semantics for this field, but it is traditional to use a string in the form
"Generating::Package version 1.23" or the author's name, if the file was generated by
hand.
license
Example:
license => [ 'perl_5' ]
license => [ 'apache_2_0', 'mozilla_1_0' ]
(Spec 2) [required] {List of one or more License Strings}
One or more licenses that apply to some or all of the files in the distribution. If
multiple licenses are listed, the distribution documentation should be consulted to
clarify the interpretation of multiple licenses.
The following list of license strings are valid:
string description
------------- -----------------------------------------------
agpl_3 GNU Affero General Public License, Version 3
apache_1_1 Apache Software License, Version 1.1
apache_2_0 Apache License, Version 2.0
artistic_1 Artistic License, (Version 1)
artistic_2 Artistic License, Version 2.0
bsd BSD License (three-clause)
freebsd FreeBSD License (two-clause)
gfdl_1_2 GNU Free Documentation License, Version 1.2
gfdl_1_3 GNU Free Documentation License, Version 1.3
gpl_1 GNU General Public License, Version 1
gpl_2 GNU General Public License, Version 2
gpl_3 GNU General Public License, Version 3
lgpl_2_1 GNU Lesser General Public License, Version 2.1
lgpl_3_0 GNU Lesser General Public License, Version 3.0
mit MIT (aka X11) License
mozilla_1_0 Mozilla Public License, Version 1.0
mozilla_1_1 Mozilla Public License, Version 1.1
openssl OpenSSL License
perl_5 The Perl 5 License (Artistic 1 & GPL 1 or later)
qpl_1_0 Q Public License, Version 1.0
ssleay Original SSLeay License
sun Sun Internet Standards Source License (SISSL)
zlib zlib License
The following license strings are also valid and indicate other licensing not described
above:
string description
------------- -----------------------------------------------
open_source Other Open Source Initiative (OSI) approved license
restricted Requires special permission from copyright holder
unrestricted Not an OSI approved license, but not restricted
unknown License not provided in metadata
All other strings are invalid in the license field.
meta-spec
Example:
'meta-spec' => {
version => '2',
url => 'http://search.cpan.org/perldoc?CPAN::Meta::Spec',
}
(Spec 1.2) [required] {Map}
This field indicates the version of the CPAN Meta Spec that should be used to interpret
the metadata. Consumers must check this key as soon as possible and abort further
metadata processing if the meta-spec version is not supported by the consumer.
The following keys are valid, but only "version" is required.
version
This subkey gives the integer Version of the CPAN Meta Spec against which the document
was generated.
url This is a URL of the metadata specification document corresponding to the given
version. This is strictly for human-consumption and should not impact the
interpretation of the document.
For the version 2 spec, either of these are recommended:
o "https://metacpan.org/pod/CPAN::Meta::Spec"
o "http://search.cpan.org/perldoc?CPAN::Meta::Spec"
name
Example:
name => 'Module-Build'
(Spec 1.0) [required] {String}
This field is the name of the distribution. This is often created by taking the "main
package" in the distribution and changing "::" to "-", but the name may be completely
unrelated to the packages within the distribution. For example, LWP::UserAgent is
distributed as part of the distribution name "libwww-perl".
release_status
Example:
release_status => 'stable'
(Spec 2) [required] {String}
This field provides the release status of this distribution. If the "version" field
contains an underscore character, then "release_status" must not be "stable."
The "release_status" field must have one of the following values:
stable
This indicates an ordinary, "final" release that should be indexed by PAUSE or other
indexers.
testing
This indicates a "beta" release that is substantially complete, but has an elevated
risk of bugs and requires additional testing. The distribution should not be
installed over a stable release without an explicit request or other confirmation from
a user. This release status may also be used for "release candidate" versions of a
distribution.
unstable
This indicates an "alpha" release that is under active development, but has been
released for early feedback or testing and may be missing features or may have serious
bugs. The distribution should not be installed over a stable release without an
explicit request or other confirmation from a user.
Consumers may use this field to determine how to index the distribution for CPAN or other
repositories in addition to or in replacement of heuristics based on version number or
file name.
version
Example:
version => '0.36'
(Spec 1.0) [required] {Version}
This field gives the version of the distribution to which the metadata structure refers.
OPTIONAL FIELDS
description
Example:
description => "Module::Build is a system for "
. "building, testing, and installing Perl modules. "
. "It is meant to ... blah blah blah ...",
(Spec 2) [optional] {String}
A longer, more complete description of the purpose or intended use of the distribution
than the one provided by the "abstract" key.
keywords
Example:
keywords => [ qw/ toolchain cpan dual-life / ]
(Spec 1.1) [optional] {List of zero or more Strings}
A List of keywords that describe this distribution. Keywords must not include whitespace.
no_index
Example:
no_index => {
file => [ 'My/Module.pm' ],
directory => [ 'My/Private' ],
package => [ 'My::Module::Secret' ],
namespace => [ 'My::Module::Sample' ],
}
(Spec 1.2) [optional] {Map}
This Map describes any files, directories, packages, and namespaces that are private to
the packaging or implementation of the distribution and should be ignored by indexing or
search tools. Note that this is a list of exclusions, and the spec does not define what to
include - see "Indexing distributions a la PAUSE" in the implementors notes for more
information.
Valid subkeys are as follows:
file
A List of relative paths to files. Paths must be specified with unix conventions.
directory
A List of relative paths to directories. Paths must be specified with unix
conventions.
[ Note: previous editions of the spec had "dir" instead of "directory" ]
package
A List of package names.
namespace
A List of package namespaces, where anything below the namespace must be ignored, but
not the namespace itself.
In the example above for "no_index", "My::Module::Sample::Foo" would be ignored, but
"My::Module::Sample" would not.
optional_features
Example:
optional_features => {
sqlite => {
description => 'Provides SQLite support',
prereqs => {
runtime => {
requires => {
'DBD::SQLite' => '1.25'
}
}
}
}
}
(Spec 2) [optional] {Map}
This Map describes optional features with incremental prerequisites. Each key of the
"optional_features" Map is a String used to identify the feature and each value is a Map
with additional information about the feature. Valid subkeys include:
description
This is a String describing the feature. Every optional feature should provide a
description
prereqs
This entry is required and has the same structure as that of the "prereqs" key. It
provides a list of package requirements that must be satisfied for the feature to be
supported or enabled.
There is one crucial restriction: the prereqs of an optional feature must not include
"configure" phase prereqs.
Consumers must not include optional features as prerequisites without explicit instruction
from users (whether via interactive prompting, a function parameter or a configuration
value, etc. ).
If an optional feature is used by a consumer to add additional prerequisites, the consumer
should merge the optional feature prerequisites into those given by the "prereqs" key
using the same semantics. See "Merging and Resolving Prerequisites" for details on
merging prerequisites.
Suggestion for disuse: Because there is currently no way for a distribution to specify a
dependency on an optional feature of another dependency, the use of "optional_feature" is
discouraged. Instead, create a separate, installable distribution that ensures the
desired feature is available. For example, if "Foo::Bar" has a "Baz" feature, release a
separate "Foo-Bar-Baz" distribution that satisfies requirements for the feature.
prereqs
Example:
prereqs => {
runtime => {
requires => {
'perl' => '5.006',
'File::Spec' => '0.86',
'JSON' => '2.16',
},
recommends => {
'JSON::XS' => '2.26',
},
suggests => {
'Archive::Tar' => '0',
},
},
build => {
requires => {
'Alien::SDL' => '1.00',
},
},
test => {
recommends => {
'Test::Deep' => '0.10',
},
}
}
(Spec 2) [optional] {Map}
This is a Map that describes all the prerequisites of the distribution. The keys are
phases of activity, such as "configure", "build", "test" or "runtime". Values are Maps in
which the keys name the type of prerequisite relationship such as "requires",
"recommends", or "suggests" and the value provides a set of prerequisite relations. The
set of relations must be specified as a Map of package names to version ranges.
The full definition for this field is given in the "Prereq Spec" section.
provides
Example:
provides => {
'Foo::Bar' => {
file => 'lib/Foo/Bar.pm',
version => '0.27_02',
},
'Foo::Bar::Blah' => {
file => 'lib/Foo/Bar/Blah.pm',
},
'Foo::Bar::Baz' => {
file => 'lib/Foo/Bar/Baz.pm',
version => '0.3',
},
}
(Spec 1.2) [optional] {Map}
This describes all packages provided by this distribution. This information is used by
distribution and automation mechanisms like PAUSE, CPAN, metacpan.org and search.cpan.org
to build indexes saying in which distribution various packages can be found.
The keys of "provides" are package names that can be found within the distribution. If a
package name key is provided, it must have a Map with the following valid subkeys:
file
This field is required. It must contain a Unix-style relative file path from the root
of the distribution directory to a file that contains or generates the package. It
may be given as "META.yml" or "META.json" to claim a package for indexing without
needing a "*.pm".
version
If it exists, this field must contains a Version String for the package. If the
package does not have a $VERSION, this field must be omitted.
resources
Example:
resources => {
license => [ 'http://dev.perl.org/licenses/' ],
homepage => 'http://sourceforge.net/projects/module-build',
bugtracker => {
web => 'http://rt.cpan.org/Public/Dist/Display.html?Name=CPAN-Meta',
mailto => 'meta-bugs AT example.com',
},
repository => {
url => 'git://github.com/dagolden/cpan-meta.git',
web => 'http://github.com/dagolden/cpan-meta',
type => 'git',
},
x_twitter => 'http://twitter.com/cpan_linked/',
}
(Spec 2) [optional] {Map}
This field describes resources related to this distribution.
Valid subkeys include:
homepage
The official home of this project on the web.
license
A List of URL's that relate to this distribution's license. As with the top-level
"license" field, distribution documentation should be consulted to clarify the
interpretation of multiple licenses provided here.
bugtracker
This entry describes the bug tracking system for this distribution. It is a Map with
the following valid keys:
web - a URL pointing to a web front-end for the bug tracker
mailto - an email address to which bugs can be sent
repository
This entry describes the source control repository for this distribution. It is a Map
with the following valid keys:
url - a URL pointing to the repository itself
web - a URL pointing to a web front-end for the repository
type - a lowercase string indicating the VCS used
Because a url like "http://myrepo.example.com/" is ambiguous as to type, producers
should provide a "type" whenever a "url" key is given. The "type" field should be the
name of the most common program used to work with the repository, e.g. "git", "svn",
"cvs", "darcs", "bzr" or "hg".
DEPRECATED FIELDS
build_requires
(Deprecated in Spec 2) [optional] {String}
Replaced by "prereqs"
configure_requires
(Deprecated in Spec 2) [optional] {String}
Replaced by "prereqs"
conflicts
(Deprecated in Spec 2) [optional] {String}
Replaced by "prereqs"
distribution_type
(Deprecated in Spec 2) [optional] {String}
This field indicated 'module' or 'script' but was considered meaningless, since many
distributions are hybrids of several kinds of things.
license_uri
(Deprecated in Spec 1.2) [optional] {URL}
Replaced by "license" in "resources"
private
(Deprecated in Spec 1.2) [optional] {Map}
This field has been renamed to "no_index".
recommends
(Deprecated in Spec 2) [optional] {String}
Replaced by "prereqs"
requires
(Deprecated in Spec 2) [optional] {String}
Replaced by "prereqs"
VERSION NUMBERS
Version Formats
This section defines the Version type, used by several fields in the CPAN Meta Spec.
Version numbers must be treated as strings, not numbers. For example, 1.200 must not be
serialized as 1.2. Version comparison should be delegated to the Perl version module,
version 0.80 or newer.
Unless otherwise specified, version numbers must appear in one of two formats:
Decimal versions
Decimal versions are regular "decimal numbers", with some limitations. They must be
non-negative and must begin and end with a digit. A single underscore may be
included, but must be between two digits. They must not use exponential notation
("1.23e-2").
version => '1.234' # OK
version => '1.23_04' # OK
version => '1.23_04_05' # Illegal
version => '1.' # Illegal
version => '.1' # Illegal
Dotted-integer versions
Dotted-integer (also known as dotted-decimal) versions consist of positive integers
separated by full stop characters (i.e. "dots", "periods" or "decimal points"). This
are equivalent in format to Perl "v-strings", with some additional restrictions on
form. They must be given in "normal" form, which has a leading "v" character and at
least three integer components. To retain a one-to-one mapping with decimal versions,
all components after the first should be restricted to the range 0 to 999. The final
component may be separated by an underscore character instead of a period.
version => 'v1.2.3' # OK
version => 'v1.2_3' # OK
version => 'v1.2.3.4' # OK
version => 'v1.2.3_4' # OK
version => 'v2009.10.31' # OK
version => 'v1.2' # Illegal
version => '1.2.3' # Illegal
version => 'v1.2_3_4' # Illegal
version => 'v1.2009.10.31' # Not recommended
Version Ranges
Some fields (prereq, optional_features) indicate the particular version(s) of some other
module that may be required as a prerequisite. This section details the Version Range
type used to provide this information.
The simplest format for a Version Range is just the version number itself, e.g. 2.4. This
means that at least version 2.4 must be present. To indicate that any version of a
prerequisite is okay, even if the prerequisite doesn't define a version at all, use the
version 0.
Alternatively, a version range may use the operators < (less than), <= (less than or
equal), > (greater than), >= (greater than or equal), == (equal), and != (not equal). For
example, the specification "< 2.0" means that any version of the prerequisite less than
2.0 is suitable.
For more complicated situations, version specifications may be AND-ed together using
commas. The specification ">= 1.2, != 1.5, < 2.0" indicates a version that must be at
least 1.2, less than 2.0, and not equal to 1.5.
PREREQUISITES
Prereq Spec
The "prereqs" key in the top-level metadata and within "optional_features" define the
relationship between a distribution and other packages. The prereq spec structure is a
hierarchical data structure which divides prerequisites into Phases of activity in the
installation process and Relationships that indicate how prerequisites should be resolved.
For example, to specify that "Data::Dumper" is "required" during the "test" phase, this
entry would appear in the distribution metadata:
prereqs => {
test => {
requires => {
'Data::Dumper' => '2.00'
}
}
}
Phases
Requirements for regular use must be listed in the "runtime" phase. Other requirements
should be listed in the earliest stage in which they are required and consumers must
accumulate and satisfy requirements across phases before executing the activity. For
example, "build" requirements must also be available during the "test" phase.
before action requirements that must be met
---------------- --------------------------------
perl Build.PL configure
perl Makefile.PL
make configure, runtime, build
Build
make test configure, runtime, build, test
Build test
Consumers that install the distribution must ensure that runtime requirements are also
installed and may install dependencies from other phases.
after action requirements that must be met
---------------- --------------------------------
make install runtime
Build install
configure
The configure phase occurs before any dynamic configuration has been attempted.
Libraries required by the configure phase must be available for use before the
distribution building tool has been executed.
build
The build phase is when the distribution's source code is compiled (if necessary) and
otherwise made ready for installation.
test
The test phase is when the distribution's automated test suite is run. Any library
that is needed only for testing and not for subsequent use should be listed here.
runtime
The runtime phase refers not only to when the distribution's contents are installed,
but also to its continued use. Any library that is a prerequisite for regular use of
this distribution should be indicated here.
develop
The develop phase's prereqs are libraries needed to work on the distribution's source
code as its author does. These tools might be needed to build a release tarball, to
run author-only tests, or to perform other tasks related to developing new versions of
the distribution.
Relationships
requires
These dependencies must be installed for proper completion of the phase.
recommends
Recommended dependencies are strongly encouraged and should be satisfied except in
resource constrained environments.
suggests
These dependencies are optional, but are suggested for enhanced operation of the
described distribution.
conflicts
These libraries cannot be installed when the phase is in operation. This is a very
rare situation, and the "conflicts" relationship should be used with great caution, or
not at all.
Merging and Resolving Prerequisites
Whenever metadata consumers merge prerequisites, either from different phases or from
"optional_features", they should merged in a way which preserves the intended semantics of
the prerequisite structure. Generally, this means concatenating the version
specifications using commas, as described in the "Version Ranges" section.
Another subtle error that can occur in resolving prerequisites comes from the way that
modules in prerequisites are indexed to distribution files on CPAN. When a module is
deleted from a distribution, prerequisites calling for that module could indicate an older
distribution should be installed, potentially overwriting files from a newer distribution.
For example, as of Oct 31, 2009, the CPAN index file contained these module-distribution
mappings:
Class::MOP 0.94 D/DR/DROLSKY/Class-MOP-0.94.tar.gz
Class::MOP::Class 0.94 D/DR/DROLSKY/Class-MOP-0.94.tar.gz
Class::MOP::Class::Immutable 0.04 S/ST/STEVAN/Class-MOP-0.36.tar.gz
Consider the case where "Class::MOP" 0.94 is installed. If a distribution specified
"Class::MOP::Class::Immutable" as a prerequisite, it could result in Class-MOP-0.36.tar.gz
being installed, overwriting any files from Class-MOP-0.94.tar.gz.
Consumers of metadata should test whether prerequisites would result in installed module
files being "downgraded" to an older version and may warn users or ignore the prerequisite
that would cause such a result.
SERIALIZATION
Distribution metadata should be serialized (as a hashref) as JSON-encoded data and
packaged with distributions as the file META.json.
In the past, the distribution metadata structure had been packed with distributions as
META.yml, a file in the YAML Tiny format (for which, see YAML::Tiny). Tools that consume
distribution metadata from disk should be capable of loading META.yml, but should prefer
META.json if both are found.
NOTES FOR IMPLEMENTORS
Extracting Version Numbers from Perl Modules
To get the version number from a Perl module, consumers should use the
"MM->parse_version($file)" method provided by ExtUtils::MakeMaker or Module::Metadata.
For example, for the module given by $mod, the version may be retrieved in one of the
following ways:
# via ExtUtils::MakeMaker
my $file = MM->_installed_file_for_module($mod);
my $version = MM->parse_version($file)
The private "_installed_file_for_module" method may be replaced with other methods for
locating a module in @INC.
# via Module::Metadata
my $info = Module::Metadata->new_from_module($mod);
my $version = $info->version;
If only a filename is available, the following approach may be used:
# via Module::Build
my $info = Module::Metadata->new_from_file($file);
my $version = $info->version;
Comparing Version Numbers
The version module provides the most reliable way to compare version numbers in all the
various ways they might be provided or might exist within modules. Given two strings
containing version numbers, $v1 and $v2, they should be converted to "version" objects
before using ordinary comparison operators. For example:
use version;
if ( version->new($v1) <=> version->new($v2) ) {
print "Versions are not equal\n";
}
If the only comparison needed is whether an installed module is of a sufficiently high
version, a direct test may be done using the string form of "eval" and the "use" function.
For example, for module $mod and version prerequisite $prereq:
if ( eval "use $mod $prereq (); 1" ) {
print "Module $mod version is OK.\n";
}
If the values of $mod and $prereq have not been scrubbed, however, this presents security
implications.
Prerequisites for dynamically configured distributions
When "dynamic_config" is true, it is an error to presume that the prerequisites given in
distribution metadata will have any relationship whatsoever to the actual prerequisites of
the distribution.
In practice, however, one can generally expect such prerequisites to be one of two things:
o The minimum prerequisites for the distribution, to which dynamic configuration will
only add items
o Whatever the distribution configured with on the releaser's machine at release time
The second case often turns out to have identical results to the first case, albeit only
by accident.
As such, consumers may use this data for informational analysis, but presenting it to the
user as canonical or relying on it as such is invariably the height of folly.
Indexing distributions a la PAUSE
While no_index tells you what must be ignored when indexing, this spec holds no opinion on
how you should get your initial candidate list of things to possibly index. For "normal"
distributions you might consider simply indexing the contents of lib/, but there are many
fascinating oddities on CPAN and many dists from the days when it was normal to put the
main .pm file in the root of the distribution archive - so PAUSE currently indexes all .pm
and .PL files that are not either (a) specifically excluded by no_index (b) in "inc",
"xt", or "t" directories, or common 'mistake' directories such as "perl5".
Or: If you're trying to be PAUSE-like, make sure you skip "inc", "xt" and "t" as well as
anything marked as no_index.
Also remember: If the META file contains a provides field, you shouldn't be indexing
anything in the first place - just use that.
SEE ALSO
o CPAN, <http://www.cpan.org/>
o JSON, <http://json.org/>
o YAML, <http://www.yaml.org/>
o CPAN
o CPANPLUS
o ExtUtils::MakeMaker
o Module::Build
o Module::Install
o CPAN::Meta::History::Meta_1_4
HISTORY
Ken Williams wrote the original CPAN Meta Spec (also known as the "META.yml spec") in 2003
and maintained it through several revisions with input from various members of the
community. In 2005, Randy Sims redrafted it from HTML to POD for the version 1.2 release.
Ken continued to maintain the spec through version 1.4.
In late 2009, David Golden organized the version 2 proposal review process. David and
Ricardo Signes drafted the final version 2 spec in April 2010 based on the version 1.4
spec and patches contributed during the proposal process.
AUTHORS
o David Golden <dagolden AT cpan.org>
o Ricardo Signes <rjbs AT cpan.org>
o Adam Kennedy <adamk AT cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2010 by David Golden, Ricardo Signes, Adam Kennedy and
Contributors.
This is free software; you can redistribute it and/or modify it under the same terms as
the Perl 5 programming language system itself.
perl v5.30.0 2023-11-23 CPAN::Meta::Spec(3perl)
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