CPAN::META::HISTORY::META_1_4(3perl)

📦
version 5.44.0 · 14 versions
, in arch rolling

💅 CPAN::Meta::History::Meta_1_4 💅

okay so bestie, welcome to the Perl Programmers Reference Guide page for CPAN::Meta::History::Meta_1_4. It's the ✨historic✨ spec for META.yml version 1.4 and honestly? it's giving archival queen. Let's get into it. 🫶

🌸 NAME 🌸

CPAN::Meta::History::Meta_1_4 — Version 1.4 metadata specification for META.yml

🎀 PREFACE 🎀

This is a historical copy of the version 1.4 specification for META.yml files, copyright by Ken Williams and licensed under the same terms as Perl itself. 💖

Modifications from the original:

  • Various spelling corrections ✏️
  • Include list of valid licenses from Module::Build 0.2807 rather than linking to the module, with minor updates to text and links to reflect versions at the time of publication. 📚
  • Fixed some dead links to point to active resources. 🔗✨

🦋 SYNOPSIS 🦋

--- #YAML:1.0
name: Module-Build
abstract: Build and install Perl modules
version: 0.20
author:
  - Ken Williams <kwilliams@cpan.org>
license: perl
distribution_type: module
requires:
  Config: 0
  Cwd: 0
  Data::Dumper: 0
  ExtUtils::Install: 0
  File::Basename: 0
  File::Compare: 0
  File::Copy: 0
  File::Find: 0
  File::Path: 0
  File::Spec: 0
  IO::File: 0
  perl: 5.005_03
recommends:
  Archive::Tar: 1.00
  ExtUtils::Install: 0.3
  ExtUtils::ParseXS: 2.02
  Pod::Text: 0
  YAML: 0.35
build_requires:
  Test: 0
resources:
  license: http://dev.perl.org/licenses/
meta-spec:
  version: 1.4
  url: http://module-build.sourceforge.net/META-spec-v1.3.html
generated_by: Module::Build version 0.20

👑 DESCRIPTION 👑

This document describes version 1.4 of the META.yml specification.

The META.yml file describes important properties of contributed Perl distributions such as the ones found on CPAN. It is typically created by tools like Module::Build, Module::Install, and ExtUtils::MakeMaker. 🛠️✨

The fields in the META.yml file are meant to be helpful for people maintaining module collections (like CPAN), for people writing installation tools (like CPAN.pm or CPANPLUS), or just for people who want to know some stuff about a distribution before downloading it and starting to install it. fr fr, it's the metadata moment. 💅

Note: The latest stable version of this specification can always be found at http://module-build.sourceforge.net/META-spec-current.html, and the latest development version (which may include things that won't make it into the stable version) can always be found at http://module-build.sourceforge.net/META-spec-blead.html. 🚨 may include things that won't make it into the stable version, she said. Iconic disclaimer behavior.

🌈 FORMAT 🌈

META.yml files are written in the YAML format (see http://www.yaml.org/). 🧚

See the following links to learn why we chose YAML instead of, say, XML or Data::Dumper:

💜 TERMINOLOGY 💜

  • distribution — This is the primary object described by the META.yml specification. 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 typically contained in a single file. Currently, we primarily talk of perl modules, but this specification should be open enough to apply to other languages as well (ex. python, ruby). Examples of modules are Class::Container, LWP::Simple, or DBD::File. 🧩

The first line of a META.yml file should be a valid YAML document header like --- #YAML:1.0. 📜

🔥 FIELDS 🔥

The rest of the META.yml file is one big YAML mapping whose keys are described here. Slay, no cap. 💅

meta-spec

Example:

meta-spec:
  version: 1.4
  url: http://module-build.sourceforge.net/META-spec-v1.3.html

(Spec 1.1) [required] {URL} This field indicates the location of the version of the META.yml specification used. 📍

name

Example:

name: Module-Build

(Spec 1.0) [required] {string} The name of the distribution which is often created by taking the "main module" in the distribution and changing :: to -. Sometimes it's completely different, however, as in the case of the libwww-perl distribution (see http://search.cpan.org/dist/libwww-perl/). 😌 sometimes it's completely different — she's mysterious like that.

version

Example:

version: 0.20

(Spec 1.0) [required] {version} The version of the distribution to which the META.yml file refers.

abstract

Example:

abstract: Build and install Perl modules.

(Spec 1.1) [required] {string} A short description of the purpose of the distribution. 🍓

author

Example:

author:
  - Ken Williams <kwilliams@cpan.org>

(Spec 1.1) [required] {list of strings} A YAML sequence indicating the author(s) of the distribution. The preferred form is author-name <email-address>. 🫶

license

Example:

license: perl

(Spec 1.0) [required] {string} The license under which this distribution may be used and redistributed.

Must be one of the following licenses:

distribution_type

Example:

distribution_type: module

(Spec 1.0) [optional] {string} What kind of stuff is contained in this distribution. Most things on CPAN are modules (which can also mean a collection of modules), but some things are scripts.

Unfortunately this field is basically meaningless, since many distributions are hybrids of several kinds of things, or some new thing, or subjectively different in focus depending on who's using them. Tools like Module::Build and MakeMaker will likely stop generating this field. 💀 not the manpage calling its own field meaningless, periodt

requires

Example:

requires:
  Data::Dumper: 0
  File::Find: 1.03

(Spec 1.0) [optional] {map} A YAML mapping indicating the Perl prerequisites this distribution requires for proper operation. The keys are the names of the prerequisites (module names or 'perl'), and the values are version specifications as described in VERSION SPECIFICATIONS. 📌

recommends

Example:

recommends:
  Data::Dumper: 0
  File::Find: 1.03

(Spec 1.0) [optional] {map} A YAML mapping indicating the Perl prerequisites this distribution recommends for enhanced operation. The keys are the names of the prerequisites (module names or 'perl'), and the values are version specifications as described in VERSION SPECIFICATIONS. ✨

ALTERNATIVE: It may be desirable to present to the user which features depend on which modules so they can make an informed decision about which recommended modules to install. 🧠

Example:

optional_features:
  foo:
    description: Provides the ability to blah.
    requires:
      Data::Dumper: 0
      File::Find: 1.03

(Spec 1.1) [optional] {map} A YAML mapping of names for optional features which are made available when its requirements are met. For each feature a description is provided along with any of requires, build_requires, and conflicts, which have the same meaning in this subcontext as described elsewhere in this document.

build_requires

Example:

build_requires:
  Data::Dumper: 0
  File::Find: 1.03

(Spec 1.0) [optional] {map} A YAML mapping indicating the Perl prerequisites required for building and/or testing of this distribution. The keys are the names of the prerequisites (module names or 'perl'), and the values are version specifications as described in "VERSION SPECIFICATIONS". These dependencies are not required after the distribution is installed. 🏗️

configure_requires

Example:

configure_requires:
  Module::Build: 0.2809
  Data::Dumper: 0
  File::Find: 1.03

(Spec 1.4) [optional] {map} A YAML mapping indicating the Perl prerequisites required before configuring this distribution. The keys are the names of the prerequisites (module names or 'perl'), and the values are version specifications as described in "VERSION SPECIFICATIONS". These dependencies are not required after the distribution is installed. ⚙️

conflicts

Example:

conflicts:
  Data::Dumper: 0
  File::Find: 1.03

(Spec 1.0) [optional] {map} A YAML mapping indicating any items that cannot be installed while this distribution is installed. This is a pretty uncommon situation. The keys for conflicts are the item names (module names or 'perl'), and the values are version specifications as described in "VERSION SPECIFICATIONS". 🚫 a pretty uncommon situation, but when it hits, it HITS

dynamic_config

Example:

dynamic_config: 0

(Spec 1.0) [optional] {boolean} — okay so picture a boolean flag that's asking one very specific question: does a Build.PL or Makefile.PL (or something like them) have to get executed when this distribution gets built, or can it be built, tested and installed purely from reading its metadata file? The big reason you'd flip this to a true value is if your module does some dynamic configuration as part of its build/install process — like asking questions, or sensing the environment, that kind of thing. 🌸

Lowkey important tea: right now Module::Build doesn't actually do anything with this flag. It's probably gonna be up to higher-level tools like CPAN to do something useful with it. But it can potentially bring lots of security, packaging, and convenience improvements. 👑

If this field is omitted, it defaults to 1 (true).

private 💀

(Deprecated) (Spec 1.0) [optional] {map} — bestie, this field got renamed. It's no_index now. See below. ⬇️

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 1.1) [optional] {map} — this is a YAML mapping that describes all the packages this distribution provides. This info can be (and, in some cases, actually is) used by distribution and automation mechanisms like PAUSE, CPAN, and search.cpan.org to build indexes saying which distribution you can find various packages in. 🔍

So when you're using tools like Module::Build that can generate the provides mapping for your distro automatically — please please please look at what it generates and make sure it makes sense. Because indexers will usually just trust the provides field if it's there, instead of scanning through the distribution files themselves to figure out packages and versions. And honestly? That's a good thing. 💅 It means you can use provides to tell the indexers precisely what you want indexed about your distribution, instead of relying on them to essentially guess what you want indexed. Main character energy: you decide.

no_index 🙈

Example:

no_index:
  file:
  - My/Module.pm
  directory:
  - My/Private
  package:
  - My::Module::Stuff
  namespace:
  - My::Module::Stuff

(Spec 1.1) [optional] {map} — a YAML mapping describing any files, directories, packages, and namespaces that are private (i.e. implementation artifacts, the behind-the-scenes stuff) and therefore not of interest to searching and indexing tools. Super useful when there's no provides field hanging around. ✨

For example, http://search.cpan.org/ excludes items listed in no_index when it's searching for POD — meaning files in these directories will not get converted to HTML and made public. Which is very handy if you've got example or test PODs that you do not want the search engine going through. 🫶

file

(Spec 1.1) [optional] — excludes any listed file(s). Bye! 👋

directory

(Spec 1.1) [optional] — excludes anything below the listed directory(ies). Go deeper, excluded.

[Note: previous editions of the spec had dir instead of directory, but I think MakeMaker and various users started using directory, so in deference we switched to that.]

package

(Spec 1.1) [optional] — excludes the listed package(s).

namespace

(Spec 1.1) [optional] — excludes anything below the listed namespace(s)... but not the listed namespace(s) themself. Careful with that one, it's giving subtle. 🧚

keywords 🔑

Example:

keywords:
  - make
  - build
  - install

(Spec 1.1) [optional] {list} — a sequence of keywords/phrases that describe this distribution. It's giving searchable. ⭐

resources 🌈

Example:

resources:
  license: http://dev.perl.org/licenses/
  homepage: http://sourceforge.net/projects/module-build
  bugtracker: http://rt.cpan.org/NoAuth/Bugs.html?Dist=Module-Build
  repository: http://sourceforge.net/cvs/?group_id=45731
  MailingList: http://lists.sourceforge.net/lists/listinfo/module-build-general

(Spec 1.1) [optional] {map} — a mapping of any URL resources related to this distribution. Now listen: all-lower-case keys — like homepage, license, and bugtracker — are reserved by this specification, because they have "official" meanings defined right here in this spec. 📜 If you want to add your own "special" entries (like that MailingList entry up there 👀), use at least one upper-case letter. Capital letters = your own lane.

The current set of official keys is:

homepage

The official home of this project on the web. 🏠

license

An URL for an official statement of this distribution's license.

bugtracker

An URL for a bug tracker (e.g. Bugzilla or RT queue) for this project. 🐛

generated_by 🛠️

Example:

generated_by: Module::Build version 0.20

(Spec 1.0) [required] {string} — indicates the tool that was used to create this META.yml file. Good form is to include both the name of the tool and its version, but this field is essentially opaque, at least for the moment. If META.yml was generated by hand, it's suggested that the author be specified here. ✍️

[Note: My meta_stats.pl script which I use to gather statistics regarding META.yml usage prefers the form listed above, i.e. it splits on /\s+version\s+/ taking the first field as the name of the tool that generated the file and the second field as version of that tool. RWS]

🌈 VERSION SPECIFICATIONS 🌈

Some fields need a version specification (ex. requires, recommends, build_requires, etc.) to say which particular version(s) of some other module might be required as a prerequisite. This section spills all the tea on the version specification formats that are currently supported. 💖

The simplest format for a version specification is just the version number itself, e.g. 2.4. This means that at least version 2.4 must be present. And if you want to say any version of a prerequisite is okay — even if the prerequisite doesn't define a version at all — use the version 0. Slay, no requirements, we love a chill dependency. 😌

You may also use the operators < (less than), <= (less than or equal), > (greater than), >= (greater than or equal), == (equal), and != (not equal). So 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. Three vibes, one requirement. Periodt. 💅

👀 SEE ALSO 👀

🕰️ HISTORY 🕰️

March 14, 2003 (Pi day) 🥧

  • Created version 1.0 of this document.

May 8, 2003

  • Added the dynamic_config field, which was missing from the initial version.

November 13, 2003

  • Added more YAML rationale articles.
  • Fixed existing link to YAML discussion thread to point to new http://nntp.x.perl.org/group/ site.
  • Added and deprecated the private field.
  • Added abstract, configure, requires_packages, requires_os, excludes_os, and no_index fields.
  • Bumped version.

November 16, 2003

  • Added generation, authored_by fields.
  • Add alternative proposal to the recommends field.
  • Add proposal for a requires_build_tools field.

December 9, 2003

  • Added link to latest version of this specification on CPAN.
  • Added section "VERSION SPECIFICATIONS".
  • Chang name from Module::Build::META-spec to CPAN::META::Specification. (yep, Chang — that's literally what it says in the original, we stan a typo 😭✨)
  • Add proposal for auto_regenerate field.

December 15, 2003

  • Add index field as a compliment to no_index
  • Add keywords field as a means to aid searching distributions.
  • Add "TERMINOLOGY" section to explain certain terms that may be ambiguous.

July 26, 2005

  • Removed a bunch of items (generation, requires_build_tools, requires_packages, configure, requires_os, excludes_os, auto_regenerate) that have never actually been supported, but were more like records of brainstorming.
  • Changed authored_by to author, since that's always been what it's actually called in actual META.yml files.
  • Added the == operator to the list of supported version-checking operators.
  • Noted that the distribution_type field is basically meaningless, and shouldn't really be used.
  • Clarified dynamic_config a bit.

August 23, 2005

  • Removed the name CPAN::META::Specification, since that implies a module that doesn't actually exist. 💀

June 12, 2007

  • Added configure_requires.

okay bestie that's the whole page, we made it, you're officially a META.yml scholar now 🎓👑

this little tour was brought to you by perl v5.44.0, dated 2026-10-17, and it lives under the name CPAN::...eta_1_4(3perl) — go forth and index responsibly 💖🌸🦋

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