# phpman > perldoc > CPAN::Meta

## NAME
    [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown) - the distribution metadata for a CPAN dist

## VERSION
    version 2.150010

## SYNOPSIS
        use v5.10;
        use strict;
        use warnings;
        use [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown);
        use [Module::Load](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad/markdown);

        my $meta = [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown)->load_file('META.json');

        printf "testing requirements for %s version %s\n",
        $meta->name,
        $meta->version;

        my $prereqs = $meta->effective_prereqs;

        for my $phase ( qw/configure runtime build test/ ) {
            say "Requirements for $phase:";
            my $reqs = $prereqs->requirements_for($phase, "requires");
            for my $module ( sort $reqs->required_modules ) {
                my $status;
                if ( eval { load $module unless $module eq 'perl'; 1 } ) {
                    my $version = $module eq 'perl' ? $] : $module->VERSION;
                    $status = $reqs->accepts_module($module, $version)
                            ? "$version ok" : "$version not ok";
                } else {
                    $status = "missing"
                };
                say "  $module ($status)";
            }
        }

## DESCRIPTION
    Software distributions released to the CPAN include a META.json or, for older distributions,
    META.yml, which describes the distribution, its contents, and the requirements for building and
    installing the distribution. The data structure stored in the META.json file is described in
    [CPAN::Meta::Spec](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3ASpec/markdown).

    [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown) provides a simple class to represent this distribution metadata (or *distmeta*),
    along with some helpful methods for interrogating that data.

    The documentation below is only for the methods of the [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown) object. For information on the
    meaning of individual fields, consult the spec.

## METHODS
  new
      my $meta = [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown)->new($distmeta_struct, \%options);

    Returns a valid [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown) object or dies if the supplied metadata hash reference fails to
    validate. Older-format metadata will be up-converted to version 2 if they validate against the
    original stated specification.

    It takes an optional hashref of options. Valid options include:

    *   lazy_validation -- if true, new will attempt to convert the given metadata to version 2
        before attempting to validate it. This means than any fixable errors will be handled by
        [CPAN::Meta::Converter](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3AConverter/markdown) before validation. (Note that this might result in invalid optional
        data being silently dropped.) The default is false.

  create
      my $meta = [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown)->create($distmeta_struct, \%options);

    This is same as "new()", except that "generated_by" and "meta-spec" fields will be generated if
    not provided. This means the metadata structure is assumed to otherwise follow the latest
    [CPAN::Meta::Spec](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3ASpec/markdown).

  load_file
      my $meta = [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown)->load_file($distmeta_file, \%options);

    Given a pathname to a file containing metadata, this deserializes the file according to its file
    suffix and constructs a new "[CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown)" object, just like "new()". It will die if the
    deserialized version fails to validate against its stated specification version.

    It takes the same options as "new()" but "lazy_validation" defaults to true.

  load_yaml_string
      my $meta = [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown)->load_yaml_string($yaml, \%options);

    This method returns a new [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown) object using the first document in the given YAML string.
    In other respects it is identical to "load_file()".

  load_json_string
      my $meta = [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown)->load_json_string($json, \%options);

    This method returns a new [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown) object using the structure represented by the given JSON
    string. In other respects it is identical to "load_file()".

  load_string
      my $meta = [CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta/markdown)->load_string($string, \%options);

    If you don't know if a string contains YAML or JSON, this method will use [Parse::CPAN::Meta](https://www.chedong.com/phpMan.php/perldoc/Parse%3A%3ACPAN%3A%3AMeta/markdown) to
    guess. In other respects it is identical to "load_file()".

  save
      $meta->save($distmeta_file, \%options);

    Serializes the object as JSON and writes it to the given file. The only valid option is
    "version", which defaults to '2'. On Perl 5.8.1 or later, the file is saved with UTF-8 encoding.

    For "version" 2 (or higher), the filename should end in '.json'. [JSON::PP](https://www.chedong.com/phpMan.php/perldoc/JSON%3A%3APP/markdown) is the default JSON
    backend. Using another JSON backend requires JSON 2.5 or later and you must set the
    $ENV{PERL_JSON_BACKEND} to a supported alternate backend like [JSON::XS](https://www.chedong.com/phpMan.php/perldoc/JSON%3A%3AXS/markdown).

    For "version" less than 2, the filename should end in '.yml'. [CPAN::Meta::Converter](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3AConverter/markdown) is used to
    generate an older metadata structure, which is serialized to YAML. [CPAN::Meta::YAML](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3AYAML/markdown) is the
    default YAML backend. You may set the $ENV{PERL_YAML_BACKEND} to a supported alternative
    backend, though this is not recommended due to subtle incompatibilities between YAML parsers on
    CPAN.

  meta_spec_version
    This method returns the version part of the "meta_spec" entry in the distmeta structure. It is
    equivalent to:

      $meta->meta_spec->{version};

  effective_prereqs
      my $prereqs = $meta->effective_prereqs;

      my $prereqs = $meta->effective_prereqs( \@feature_identifiers );

    This method returns a [CPAN::Meta::Prereqs](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3APrereqs/markdown) object describing all the prereqs for the
    distribution. If an arrayref of feature identifiers is given, the prereqs for the identified
    features are merged together with the distribution's core prereqs before the [CPAN::Meta::Prereqs](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3APrereqs/markdown)
    object is returned.

  should_index_file
      ... if $meta->should_index_file( $filename );

    This method returns true if the given file should be indexed. It decides this by checking the
    "file" and "directory" keys in the "no_index" property of the distmeta structure. Note that
    neither the version format nor "release_status" are considered.

    $filename should be given in unix format.

  should_index_package
      ... if $meta->should_index_package( $package );

    This method returns true if the given package should be indexed. It decides this by checking the
    "package" and "namespace" keys in the "no_index" property of the distmeta structure. Note that
    neither the version format nor "release_status" are considered.

  features
      my @feature_objects = $meta->features;

    This method returns a list of [CPAN::Meta::Feature](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3AFeature/markdown) objects, one for each optional feature
    described by the distribution's metadata.

  feature
      my $feature_object = $meta->feature( $identifier );

    This method returns a [CPAN::Meta::Feature](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3AFeature/markdown) object for the optional feature with the given
    identifier. If no feature with that identifier exists, an exception will be raised.

  as_struct
      my $copy = $meta->as_struct( \%options );

    This method returns a deep copy of the object's metadata as an unblessed hash reference. It
    takes an optional hashref of options. If the hashref contains a "version" argument, the copied
    metadata will be converted to the version of the specification and returned. For example:

      my $old_spec = $meta->as_struct( {version => "1.4"} );

  as_string
      my $string = $meta->as_string( \%options );

    This method returns a serialized copy of the object's metadata as a character string. (The
    strings are not UTF-8 encoded.) It takes an optional hashref of options. If the hashref contains
    a "version" argument, the copied metadata will be converted to the version of the specification
    and returned. For example:

      my $string = $meta->as_string( {version => "1.4"} );

    For "version" greater than or equal to 2, the string will be serialized as JSON. For "version"
    less than 2, the string will be serialized as YAML. In both cases, the same rules are followed
    as in the "save()" method for choosing a serialization backend.

    The serialized structure will include a "x_serialization_backend" entry giving the package and
    version used to serialize. Any existing key in the given $meta object will be clobbered.

## STRING DATA
    The following methods return a single value, which is the value for the corresponding entry in
    the distmeta structure. Values should be either undef or strings.

    *   abstract

    *   description

    *   dynamic_config

    *   generated_by

    *   name

    *   release_status

    *   version

## LIST DATA
    These methods return lists of string values, which might be represented in the distmeta
    structure as arrayrefs or scalars:

    *   authors

    *   keywords

    *   licenses

    The "authors" and "licenses" methods may also be called as "author" and "license", respectively,
    to match the field name in the distmeta structure.

## MAP DATA
    These readers return hashrefs of arbitrary unblessed data structures, each described more fully
    in the specification:

    *   meta_spec

    *   resources

    *   provides

    *   no_index

    *   prereqs

    *   optional_features

## CUSTOM DATA
    A list of custom keys are available from the "custom_keys" method and particular keys may be
    retrieved with the "custom" method.

      say $meta->custom($_) for $meta->custom_keys;

    If a custom key refers to a data structure, a deep clone is returned.

## BUGS
    Please report any bugs or feature using the CPAN Request Tracker. Bugs can be submitted through
    the web interface at <<http://rt.cpan.org/Dist/Display.html?Queue=CPAN-Meta>>

    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.

## SEE ALSO
    *   [CPAN::Meta::Converter](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3AConverter/markdown)

    *   [CPAN::Meta::Validator](https://www.chedong.com/phpMan.php/perldoc/CPAN%3A%3AMeta%3A%3AValidator/markdown)

## SUPPORT
  Bugs / Feature Requests
    Please report any bugs or feature requests through the issue tracker at
    <<https://github.com/Perl-Toolchain-Gang/CPAN-Meta/issues>>. You will be notified automatically of
    any progress on your issue.

### Source Code
    This is open source software. The code repository is available for public review and
    contribution under the terms of the license.

    <<https://github.com/Perl-Toolchain-Gang/CPAN-Meta>>

      git clone <https://github.com/Perl-Toolchain-Gang/CPAN-Meta.git>

## AUTHORS
    *   David Golden <<dagolden@cpan.org>>

    *   Ricardo Signes <<rjbs@cpan.org>>

    *   Adam Kennedy <<adamk@cpan.org>>

## CONTRIBUTORS
    *   Ansgar Burchardt <<ansgar@cpan.org>>

    *   Avar Arnfjord Bjarmason <<avar@cpan.org>>

    *   Benjamin Noggle <<agwind@users.noreply.github.com>>

    *   Christopher J. Madsen <<cjm@cpan.org>>

    *   Chuck Adams <<cja987@gmail.com>>

    *   Cory G Watson <<gphat@cpan.org>>

    *   Damyan Ivanov <<dam@cpan.org>>

    *   David Golden <<xdg@xdg.me>>

    *   Eric Wilhelm <<ewilhelm@cpan.org>>

    *   Graham Knop <<haarg@haarg.org>>

    *   Gregor Hermann <<gregoa@debian.org>>

    *   Karen Etheridge <<ether@cpan.org>>

    *   Kenichi Ishigaki <<ishigaki@cpan.org>>

    *   Kent Fredric <<kentfredric@gmail.com>>

    *   Ken Williams <<kwilliams@cpan.org>>

    *   Lars Dieckow <<daxim@cpan.org>>

    *   Leon Timmermans <<leont@cpan.org>>

    *   majensen <<maj@fortinbras.us>>

    *   Mark Fowler <<markf@cpan.org>>

    *   Matt S Trout <<mst@shadowcat.co.uk>>

    *   Michael G. Schwern <<mschwern@cpan.org>>

    *   Mohammad S Anwar <<mohammad.anwar@yahoo.com>>

    *   mohawk2 <<mohawk2@users.noreply.github.com>>

    *   moznion <<moznion@gmail.com>>

    *   Niko Tyni <<ntyni@debian.org>>

    *   Olaf Alders <<olaf@wundersolutions.com>>

    *   Olivier Mengué <<dolmen@cpan.org>>

    *   Randy Sims <<randys@thepierianspring.org>>

    *   Tomohiro Hosaka <<bokutin@bokut.in>>

## 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.