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✏️ Editing: META-spec-1_4.pod

=head1 NAME

META-spec - Specification for F<META.yml> documents

=head1 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

=head1 DESCRIPTION

This document describes version 1.4 of the F<META.yml> specification.

The F<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 F<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.

I<Note: The latest stable version of this specification can always be
found at L<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
L<http://module-build.sourceforge.net/META-spec-blead.html>.>

=begin MAINTAINER

The master source for the META spec is META-spec.pod.  META-spec.html
is built (manually) from META-spec.pod whenever there are changes, and
the two files should generally be checked in together.  Ideally it
would happen through a trigger or something, but it doesn't.

Ken has a cron job that copies the latest bleeding-edge version of the
spec (HTML version) to Sourceforge whenever his laptop is turned on:

21 * * * * svn cat http://svn.perl.org/modules/Module-Build/trunk/website/META-spec.html \
       | ssh kwilliams@shell.sourceforge.net \
       'cat > /home/groups/m/mo/module-build/htdocs/META-spec-blead.html'

The numbered revisions of the spec at
L<"http://module-build.sourceforge.net/"> are captures of the spec at
opportune moments.  A couple of symlinks also exist for convenience:

-rw-r--r--  1 kwilliams 24585 Oct 10 17:21 META-spec-blead.html
 lrwxrwxrwx  1 kwilliams    19 Jan 19  2007 META-spec-current.html -> META-spec-v1.3.html
 lrwxrwxrwx  1 kwilliams    22 Jan 19  2007 META-spec.html -> META-spec-current.html
 -rw-r--r--  1 kwilliams  5830 Jul 25  2005 META-spec-v1.0.html
 -rw-r--r--  1 kwilliams  7847 Jul 25  2005 META-spec-v1.1.html
 -rw-r--r--  1 kwilliams 22635 Aug 23  2005 META-spec-v1.2.html
 -rw-r--r--  1 kwilliams 24086 Nov  4  2006 META-spec-v1.3.html

=end MAINTAINER

=head1 FORMAT

F<META.yml> files are written in the YAML format (see
L<http://www.yaml.org/>).

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

=over 4

=item Module::Build design plans

L<http://nntp.x.perl.org/group/perl.makemaker/406>

=item Not keen on YAML

L<http://nntp.x.perl.org/group/perl.module-authors/1353>

=item META Concerns

L<http://nntp.x.perl.org/group/perl.module-authors/1385>

=back

=head1 TERMINOLOGY

=over 4

=item distribution

This is the primary object described by the F<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
C<Class-Container>, C<libwww-perl>, or C<DBI>.

=item 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 C<Class::Container>,
C<LWP::Simple>, or C<DBD::File>.

=back

=head1 HEADER

The first line of a F<META.yml> file should be a valid YAML document
header like C<"--- #YAML:1.0">.

=head1 FIELDS

The rest of the F<META.yml> file is one big YAML mapping whose keys
are described here.

=head2 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.

=head2 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 libww-perl distribution (see
L<http://search.cpan.org/dist/libwww-perl/>).

=head2 version

Example:

version: 0.20

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

=head2 abstract

Example:

abstract: Build and install Perl modules.

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

=head2 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 prefered form is author-name <email-address>.

=head2 license

Example:

license: perl

(Spec 1.0) [required] {string} The license under which this
distribution may be used and redistributed.  See
L<http://search.cpan.org/dist/Module-Build/lib/Module/Build/API.pod>
for the list of valid options.

=head2 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 C<module>s (which can also mean
a collection of modules), but some things are C<script>s.

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.

=head2 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 L<VERSION
SPECIFICATIONS>.

=head2 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 L<VERSION
SPECIFICATIONS>.

I<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

I<(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 L<"requires">,
L<"build_requires">, and L<"conflicts">, which have the same meaning in
this subcontext as described elsewhere in this document.>

=head2 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 L<VERSION SPECIFICATIONS>.  These dependencies are not
required after the distribution is installed.

=head2 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 L<VERSION SPECIFICATIONS>.  These dependencies are not required
after the distribution is installed.

=head2 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 C<conflicts> are the item
names (module names or 'perl'), and the values are version
specifications as described in L<VERSION SPECIFICATIONS>.

=head2 dynamic_config

Example:

dynamic_config: 0

(Spec 1.0) [optional] {boolean} A boolean flag indicating whether a F<Build.PL>
or F<Makefile.PL> (or similar) must be executed when building this
distribution, or whether it can be built, tested and installed solely
from consulting its
metadata file.  The main reason to set this to a true value is that
your module performs some dynamic configuration (asking questions,
sensing the environment, etc.) as part of its build/install process.

Currently Module::Build doesn't actually do anything with this flag
- it's probably going to be up to higher-level tools like CPAN
to do something useful with it.  It can potentially bring lots of
security, packaging, and convenience improvements.

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

=head2 private

I<(Deprecated)> (Spec 1.0) [optional] {map} This field has been renamed to
L</"no_index">.  See below.

=head2 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} A YAML mapping that describes all packages
provided by this distribution.  This information can be (and, in some
cases, is) used by distribution and automation mechanisms like PAUSE,
CPAN, and search.cpan.org to build indexes saying in which
distribution various packages can be found.

When using tools like C<Module::Build> that can generate the
C<provides> mapping for your distribution automatically, make sure you
examine what it generates to make sure it makes sense - indexers will
usually trust the C<provides> field if it's present, rather than
scanning through the distribution files themselves to figure out
packages and versions.  This is a good thing, because it means you can
use the C<provides> field to tell the indexers precisely what you want
indexed about your distribution, rather than relying on them to
essentially guess what you want indexed.

=head2 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 that describes any files,
directories, packages, and namespaces that are private
(i.e. implementation artifacts) that are not of interest to searching
and indexing tools.  This is useful when no C<provides> field is
present.

For example, C<search.cpan.org> excludes items listed in C<no_index>
when searching for POD, meaning files in these directories will not
converted to HTML and made public - which is useful if you have
example or test PODs that you don't want the search engine to go
through.

=head3 file

(Spec 1.1) [optional] Exclude any listed file(s).

=head3 directory

(Spec 1.1) [optional] Exclude anything below the listed
directory(ies).

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

=head3 package

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

=head3 namespace

(Spec 1.1) [optional] Excludes anything below the listed namespace(s),
but I<not> the listed namespace(s) its self.

=head2 keywords

Example:

keywords:
    - make
    - build
    - install

(Spec 1.1) [optional] {list} A sequence of keywords/phrases that describe
this distribution.

=head2 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.  All-lower-case keys, such as C<homepage>,
C<license>, and C<bugtracker>, are reserved by this specification, as
they have "official" meanings defined here in this specification.  If
you'd like to add your own "special" entries (like the "MailingList"
entry above), use at least one upper-case letter.

The current set of official keys is:

=over 2

=item homepage

The official home of this project on the web.

=item license

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

=item bugtracker

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

=back

=head2 generated_by

Example:

generated_by: Module::Build version 0.20

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

[Note: My F<meta_stats.pl> script which I use to gather statistics
regarding F<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]

=head1 VERSION SPECIFICATIONS

Some fields require a version specification (ex. L<"requires">,
L<"recommends">, L<"build_requires">, etc.) to indicate the particular
versionZ<>(s) of some other module that may be required as a
prerequisite.  This section details the version specification formats
that are currently supported.

The simplest format for a version specification is just the version
number itself, e.g. C<2.4>.  This means that B<at least> version 2.4
must be present.  To indicate that B<any> version of a prerequisite is
okay, even if the prerequisite doesn't define a version at all, use
the version C<0>.

You may also use the operators E<lt> (less than), E<lt>= (less than or
equal), E<gt> (greater than), E<gt>= (greater than or equal), ==
(equal), and != (not equal).  For example, the specification C<E<lt>
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 C<E<gt>= 1.2, != 1.5, E<lt>
2.0> indicates a version that must be B<at least> 1.2, B<less than>
2.0, and B<not equal to> 1.5.

=head1 SEE ALSO

CPAN, L<http://www.cpan.org/>

CPAN.pm, L<http://search.cpan.org/dist/CPAN/>

CPANPLUS, L<http://search.cpan.org/dist/CPANPLUS/>

Data::Dumper, L<http://search.cpan.org/dist/Data-Dumper/>

ExtUtils::MakeMaker, L<http://search.cpan.org/dist/ExtUtils-MakeMaker/>

Module::Build, L<http://search.cpan.org/dist/Module-Build/>

Module::Install, L<http://search.cpan.org/dist/Module-Install/>

XML, L<http://www.w3.org/XML/>

YAML, L<http://www.yaml.org/>

=head1 HISTORY

=over 4

=item March 14, 2003 (Pi day)

=over 2

=item *

Created version 1.0 of this document.

=back

=item May 8, 2003

=over 2

=item *

Added the L</"dynamic_config"> field, which was missing from the initial
version.

=back

=item November 13, 2003

=over 2

=item *

Added more YAML rationale articles.

=item *

Fixed existing link to YAML discussion thread to point to new
L<http://nntp.x.perl.org/group/> site.

=item *

Added and deprecated the L<"private"> field.

=item *

Added L<"abstract">, L<"configure">, L<"requires_packages">,
L<"requires_os">, L<"excludes_os">, and L<"no_index"> fields.

=item *

Bumped version.

=back

=item November 16, 2003

=over 2

=item *

Added L<"generation">, L<"authored_by"> fields.

=item *

Add alternative proposal to the L<"recommends"> field.

=item *

Add proposal for a L<"requires_build_tools"> field.

=back

=item December 9, 2003

=over 2

=item *

Added link to latest version of this specification on CPAN.

=item *

Added section L<"VERSION SPECIFICATIONS">.

=item *

Chang name from Module::Build::META-spec to CPAN::META::Specification.

=item *

Add proposal for L<"auto_regenerate"> field.

=back

=item December 15, 2003

=over 2

=item *

Add L<"index"> field as a compliment to L<"no_index">

=item *

Add L<"keywords"> field as a means to aid searching distributions.

=item *

Add L<"TERMINOLOGY"> section to explain certain terms that may be
ambiguous.

=back

=item July 26, 2005

=over 2

=item *

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.

=item *

Changed C<authored_by> to C<author>, since that's always been what
it's actually called in actual F<META.yml> files.

=item *

Added the "==" operator to the list of supported version-checking
operators.

=item *

Noted that the C<distribution_type> field is basically meaningless,
and shouldn't really be used.

=item *

Clarified C<dynamic_config> a bit.

=back

=item August 23, 2005

=over 2

=item *

Removed the name C<CPAN::META::Specification>, since that implies a
module that doesn't actually exist.

=back

=item June 12, 2007

=over 2

=item *

Added C<configure_requires>.

=back

MR SKB