CPAN::...eta_1_2(3perl) Perl Programmers Reference GuideCPAN::...eta_1_2(3perl)
NAME
CPAN::Meta::History::Meta_1_2 - Version 1.2 metadata specification for
META.yml
PREFACE
This is a historical copy of the version 1.2 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 0.2611 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
urls:
license: http://dev.perl.org/licenses/
meta-spec:
version: 1.2
url: http://module-build.sourceforge.net/META-spec-v1.2.html
generated_by: Module::Build version 0.20
DESCRIPTION
This document describes version 1.2 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.
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>.
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:
• Module::Build design plans
<http://www.nntp.perl.org/group/perl.makemaker/2002/04/msg407.html>
• Not keen on YAML <http://www.nntp.perl.org/group/perl.module-
authors/2003/11/msg1353.html>
• META Concerns <http://www.nntp.perl.org/group/perl.module-
authors/2003/11/msg1385.html>
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 for other
developers to use.
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).
VERSION SPECIFICATIONS
Some fields require a version specification (ex. "requires",
"recommends", "build_requires", etc.). This section details the version
specifications that are currently supported.
If a single version is listed, then that version is considered to be the
minimum version supported.
If 0 is given as the version number, then any version is supported.
Additionally, for more complicated requirements, the specification
supports a list of versions, each of which may be optionally preceded by
a relational operator.
Supported operators include < (less than), <= (less than or equal), >
(greater than), >= (greater than or equal), == (equal), and != (not
equal).
If a list is given then it is evaluated from left to right so that any
specifications in the list that conflict with a previous specification
are overridden by the later.
Examples:
>= 1.2, != 1.5, < 2.0
Any version from version 1.2 onward, except version 1.5, that also
precedes version 2.0.
HEADER
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.
meta-spec
Example:
meta-spec:
version: 1.2
url: http://module-build.sourceforge.net/META-spec-v1.2.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/author/GAAS/libwww-perl/>).
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:
perl
The distribution may be copied and redistributed under the same
terms as perl itself (this is by far the most common licensing
option for modules on CPAN). This is a dual license, in which the
user may choose between either the GPL version 1 or the Artistic
version 1 license.
gpl The distribution is distributed under the terms of the GNU General
Public License version 2 (<http://opensource.org/licenses/GPL-2.0>).
lgpl
The distribution is distributed under the terms of the GNU Lesser
General Public License version 2
(<http://opensource.org/licenses/LGPL-2.1>).
artistic
The distribution is licensed under the Artistic License version 1,
as specified by the Artistic file in the standard perl distribution
(<http://opensource.org/licenses/Artistic-Perl-1.0>).
bsd The distribution is licensed under the BSD 3-Clause License
(<http://opensource.org/licenses/BSD-3-Clause>).
open_source
The distribution is licensed under some other Open Source
Initiative-approved license listed at
<http://www.opensource.org/licenses/>.
unrestricted
The distribution is licensed under a license that is not approved by
www.opensource.org <http://www.opensource.org/> but that allows
distribution without restrictions.
restrictive
The distribution may not be redistributed without special permission
from the author and/or copyright holder.
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 "module"s (which can also mean a
collection of modules), but some things are "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.
requires
Example:
requires:
Data::Dumper: 0
File::Find: 1.03
(Spec 1.0) [optional] {map} A YAML mapping indicating the Perl modules
this distribution requires for proper operation. The keys are the
module names, and the values are version specifications as described in
Module::Build for the "requires" parameter.
recommends
Example:
recommends:
Data::Dumper: 0
File::Find: 1.03
(Spec 1.0) [optional] {map} A YAML mapping indicating the Perl modules
this distribution recommends for enhanced operation.
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
- bar:
description: This feature is not available on this platform.
excludes_os: MSWin32
(Spec 1.1) [optional] {map} A YAML sequence 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", "conflicts", "requires_packages", "requires_os", and
"excludes_os" 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 modules
required for building and/or testing of this distribution. These
dependencies are not required after the module is installed.
conflicts
Example:
conflicts:
Data::Dumper: 0
File::Find: 1.03
(Spec 1.0) [optional] {map} A YAML mapping indicating the Perl modules
that cannot be installed while this distribution is installed. This is
a pretty uncommon situation.
dynamic_config
Example:
dynamic_config: 0
(Spec 1.0) [optional] {boolean} A boolean flag indicating whether a
Build.PL or 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 if 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).
private
(Deprecated) (Spec 1.0) [optional] {map} This field has been renamed to
"no_index". 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} 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 Module::Build that can generate the "provides"
mapping for your distribution automatically, make sure you examine what
it generates to make sure it makes sense - indexers will usually trust
the "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 "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.
no_index
Example:
no_index:
file:
- My/Module.pm
dir:
- 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 "provides" field is present.
(Note: I'm not actually sure who looks at this field, or exactly what
they do with it. This spec could be off in some way from actual usage.)
file
(Spec 1.1) [optional] Exclude any listed file(s).
dir
(Spec 1.1) [optional] Exclude anything below the listed directory(ies).
package
(Spec 1.1) [optional] Exclude the listed package(s).
namespace
(Spec 1.1) [optional] Excludes anything below the listed namespace(s),
but not the listed namespace(s) its self.
keywords
Example:
keywords:
- make
- build
- install
(Spec 1.1) [optional] {list} A sequence of keywords/phrases that
describe this distribution.
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
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 "homepage", "license",
and "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:
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. 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 META.yml was generated by hand, it is 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]
SEE ALSO
CPAN <http://www.cpan.org/>
CPAN.pm
CPANPLUS
Data::Dumper
ExtUtils::MakeMaker
Module::Build
Module::Install
XML <http://www.w3.org/XML/>
YAML <http://www.yaml.org/>
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.
• 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.
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