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Parse::CPAN::Meta - Parse META.yml and META.json CPAN metadata files
Contents
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 v5.40.1 2025-07-03 Parse::CPAN::Meta(3perl)
Description
Parse::CPAN::Meta is a parser for META.json and META.yml files, using JSON::PP and/or CPAN::Meta::YAML.
Parse::CPAN::Meta provides three methods: "load_file", "load_json_string", and "load_yaml_string". These
will read and deserialize CPAN metafiles, and are described below in detail.
Parse::CPAN::Meta provides a legacy API of only two functions, based on the YAML functions of the same
name. Wherever possible, identical calling semantics are used. These may only be used with YAML sources.
All error reporting is done with exceptions (die'ing).
Note that META files are expected to be in UTF-8 encoding, only. When converted string data, it must
first be decoded from UTF-8.
Environment
CPAN_META_JSON_DECODER
By default, JSON::PP will be used for deserializing JSON data. If the "CPAN_META_JSON_DECODER"
environment variable exists, this is expected to be the name of a loadable module that provides a
"decode_json" subroutine, which will then be used for deserialization. Relying only on the existence of
said subroutine allows for maximum compatibility, since this API is provided by all of JSON::PP,
JSON::XS, Cpanel::JSON::XS, JSON::MaybeXS, JSON::Tiny, and Mojo::JSON.
CPAN_META_JSON_BACKEND
By default, JSON::PP will be used for deserializing JSON data. If the "CPAN_META_JSON_BACKEND"
environment variable exists, this is expected to be the name of a loadable module that provides the JSON
API, since downstream code expects to be able to call "new" on this class. As such, while JSON::PP,
JSON::XS, Cpanel::JSON::XS and JSON::MaybeXS will work for this, to use Mojo::JSON or JSON::Tiny for
decoding requires setting "CPAN_META_JSON_DECODER".
PERL_JSON_BACKEND
If the "CPAN_META_JSON_BACKEND" environment variable does not exist, and if "PERL_JSON_BACKEND"
environment variable exists, is true and is not "JSON::PP", then the JSON module (version 2.5 or greater)
will be loaded and used to interpret "PERL_JSON_BACKEND". If JSON is not installed or is too old, an
exception will be thrown. Note that at the time of writing, the only useful values are 1, which will
tell JSON to guess, or JSON::XS - if you want to use a newer JSON module, see "CPAN_META_JSON_BACKEND".
PERL_YAML_BACKEND
By default, CPAN::Meta::YAML will be used for deserializing YAML data. If the "PERL_YAML_BACKEND"
environment variable is defined, then it is interpreted as a module to use for deserialization. The
given module must be installed, must load correctly and must implement the Load() function or an
exception will be thrown.
Functions
For maintenance clarity, no functions are exported by default. These functions are available for
backwards compatibility only and are best avoided in favor of "load_file".
Load
my @yaml = Parse::CPAN::Meta::Load( $string );
Parses a string containing a valid YAML stream into a list of Perl data structures.
LoadFile
my @yaml = Parse::CPAN::Meta::LoadFile( 'META.yml' );
Reads the YAML stream from a file instead of a string.
Methods
load_file
my $metadata_structure = Parse::CPAN::Meta->load_file('META.json');
my $metadata_structure = Parse::CPAN::Meta->load_file('META.yml');
This method will read the named file and deserialize it to a data structure, determining whether it
should be JSON or YAML based on the filename. The file will be read using the ":utf8" IO layer.
load_yaml_string
my $metadata_structure = Parse::CPAN::Meta->load_yaml_string($yaml_string);
This method deserializes the given string of YAML and returns the first document in it. (CPAN metadata
files should always have only one document.) If the source was UTF-8 encoded, the string must be decoded
before calling "load_yaml_string".
load_json_string
my $metadata_structure = Parse::CPAN::Meta->load_json_string($json_string);
This method deserializes the given string of JSON and the result. If the source was UTF-8 encoded, the
string must be decoded before calling "load_json_string".
load_string
my $metadata_structure = Parse::CPAN::Meta->load_string($some_string);
If you don't know whether a string contains YAML or JSON data, this method will use some heuristics and
guess. If it can't tell, it assumes YAML.
yaml_backend
my $backend = Parse::CPAN::Meta->yaml_backend;
Returns the module name of the YAML serializer. See "ENVIRONMENT" for details.
json_backend
my $backend = Parse::CPAN::Meta->json_backend;
Returns the module name of the JSON serializer. If "CPAN_META_JSON_BACKEND" is set, this will be
whatever that's set to. If not, this will either be JSON::PP or JSON. If "PERL_JSON_BACKEND" is set,
this will return JSON as further delegation is handled by the JSON module. See "ENVIRONMENT" for
details.
json_decoder
my $decoder = Parse::CPAN::Meta->json_decoder;
Returns the module name of the JSON decoder. Unlike "json_backend", this is not necessarily a full
JSON-style module, but only something that will provide a "decode_json" subroutine. If
"CPAN_META_JSON_DECODER" is set, this will be whatever that's set to. If not, this will be whatever has
been selected as "json_backend". See "ENVIRONMENT" for more notes.
Name
Parse::CPAN::Meta - Parse META.yml and META.json CPAN metadata files
Synopsis
#############################################
# In your file
---
name: My-Distribution
version: 1.23
resources:
homepage: "http://example.com/dist/My-Distribution"
#############################################
# In your program
use Parse::CPAN::Meta;
my $distmeta = Parse::CPAN::Meta->load_file('META.yml');
# Reading properties
my $name = $distmeta->{name};
my $version = $distmeta->{version};
my $homepage = $distmeta->{resources}{homepage};
Version
version 2.150010
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