CPAN::Meta::Spec(3p) Perl Programmers Reference Guide CPAN::Meta::Spec(3p) #
CPAN::Meta::Spec(3p) Perl Programmers Reference Guide CPAN::Meta::Spec(3p)
NNAAMMEE #
CPAN::Meta::Spec - specification for CPAN distribution metadata
VVEERRSSIIOONN #
version 2.150010
SSYYNNOOPPSSIISS #
my $distmeta = {
name => 'Module-Build',
abstract => 'Build and install Perl modules',
description => "Module::Build is a system for "
. "building, testing, and installing Perl modules. "
. "It is meant to ... blah blah blah ...",
version => '0.36',
release_status => 'stable',
author => [
'Ken Williams <kwilliams@cpan.org>',
'Module-Build List <module-build@perl.org>', # additional contact
],
license => [ 'perl_5' ],
prereqs => {
runtime => {
requires => {
'perl' => '5.006',
'ExtUtils::Install' => '0',
'File::Basename' => '0',
'File::Compare' => '0',
'IO::File' => '0',
},
recommends => {
'Archive::Tar' => '1.00',
'ExtUtils::Install' => '0.3',
'ExtUtils::ParseXS' => '2.02',
},
},
build => {
requires => {
'Test::More' => '0',
},
}
},
resources => {
license => ['http://dev.perl.org/licenses/'],
},
optional_features => {
domination => {
description => 'Take over the world',
prereqs => {
develop => { requires => { 'Genius::Evil' => '1.234' } },
runtime => { requires => { 'Machine::Weather' => '2.0' } },
},
},
},
dynamic_config => 1,
keywords => [ qw/ toolchain cpan dual-life / ],
'meta-spec' => {
version => '2',
url => 'https://metacpan.org/pod/CPAN::Meta::Spec',
},
generated_by => 'Module::Build version 0.36',
};
DDEESSCCRRIIPPTTIIOONN #
This document describes version 2 of the CPAN distribution metadata
specification, also known as the "CPAN Meta Spec".
Revisions of this specification for typo corrections and prose
clarifications may be issued as CPAN::Meta::Spec 2._x. These revisions
will never change semantics or add or remove specified behavior.
Distribution metadata describe important properties of Perl
distributions. Distribution building tools like Module::Build,
Module::Install, ExtUtils::MakeMaker or Dist::Zilla should create a
metadata file in accordance with this specification and include it with
the distribution for use by automated tools that index, examine, package
or install Perl distributions.
TTEERRMMIINNOOLLOOGGYY #
distribution
This is the primary object described by the metadata. 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 contained in a single file.
Modules usually contain one or more packages and are often referred
to by the name of a primary package that can be mapped to the file
name. For example, one might refer to "File::Spec" instead of
_F_i_l_e_/_S_p_e_c_._p_m
package
This refers to a namespace declared with the Perl "package"
statement. In Perl, packages often have a version number property
given by the $VERSION variable in the namespace.
consumer
This refers to code that reads a metadata file, deserializes it into
a data structure in memory, or interprets a data structure of
metadata elements.
producer
This refers to code that constructs a metadata data structure,
serializes into a bytestream and/or writes it to disk.
must, should, may, etc.
These terms are interpreted as described in IETF RFC 2119.
DDAATTAA TTYYPPEESS #
Fields in the "STRUCTURE" section describe data elements, each of which
has an associated data type as described herein. There are four
primitive types: Boolean, String, List and Map. Other types are subtypes
of primitives and define compound data structures or define constraints
on the values of a data element.
BBoooolleeaann A _B_o_o_l_e_a_n is used to provide a true or false value. It mmuusstt be represented as a defined value that is either “1” or “0” or stringifies to those values.
SSttrriinngg A _S_t_r_i_n_g is data element containing a non-zero length sequence of Unicode characters, such as an ordinary Perl scalar that is not a reference.
LLiisstt A _L_i_s_t is an ordered collection of zero or more data elements. Elements of a List may be of mixed types.
Producers mmuusstt represent List elements using a data structure which
unambiguously indicates that multiple values are possible, such as a
reference to a Perl array (an "arrayref").
Consumers expecting a List mmuusstt consider a String as equivalent to a List
of length 1.
MMaapp A _M_a_p is an unordered collection of zero or more data elements (“values”), indexed by associated String elements (“keys”). The Map’s value elements may be of mixed types.
LLiicceennssee SSttrriinngg A _L_i_c_e_n_s_e _S_t_r_i_n_g is a subtype of String with a restricted set of values. Valid values are described in detail in the description of the “license” field.
UURRLL #
_U_R_L is a subtype of String containing a Uniform Resource Locator or
Identifier. [ This type is called URL and not URI for historical
reasons. ]
VVeerrssiioonn A _V_e_r_s_i_o_n is a subtype of String containing a value that describes the version number of packages or distributions. Restrictions on format are described in detail in the “Version Formats” section.
VVeerrssiioonn RRaannggee The _V_e_r_s_i_o_n _R_a_n_g_e type is a subtype of String. It describes a range of Versions that may be present or installed to fulfill prerequisites. It is specified in detail in the “Version Ranges” section.
SSTTRRUUCCTTUURREE #
The metadata structure is a data element of type Map. This section
describes valid keys within the Map.
Any keys not described in this specification document (whether top-level
or within compound data structures described herein) are considered
_c_u_s_t_o_m _k_e_y_s and mmuusstt begin with an "x" or "X" and be followed by an
underscore; i.e. they must match the pattern: "qr{\Ax_}i". If a custom
key refers to a compound data structure, subkeys within it do not need an
"x_" or "X_" prefix.
Consumers of metadata may ignore any or all custom keys. All other keys
not described herein are invalid and should be ignored by consumers.
Producers must not generate or output invalid keys.
For each key, an example is provided followed by a description. The
description begins with the version of spec in which the key was added or
in which the definition was modified, whether the key is _r_e_q_u_i_r_e_d or
_o_p_t_i_o_n_a_l and the data type of the corresponding data element. These
items are in parentheses, brackets and braces, respectively.
If a data type is a Map or Map subtype, valid subkeys will be described
as well.
Some fields are marked _D_e_p_r_e_c_a_t_e_d. These are shown for historical
context and must not be produced in or consumed from any metadata
structure of version 2 or higher.
RREEQQUUIIRREEDD FFIIEELLDDSS #
_a_b_s_t_r_a_c_t
Example:
abstract => 'Build and install Perl modules'
(Spec 1.2) [required] {String}
This is a short description of the purpose of the distribution.
_a_u_t_h_o_r
Example:
author => [ 'Ken Williams <kwilliams@cpan.org>' ]
(Spec 1.2) [required] {List of one or more Strings}
This List indicates the person(s) to contact concerning the distribution.
The preferred form of the contact string is:
contact-name <email-address>
This field provides a general contact list independent of other
structured fields provided within the "resources" field, such as
"bugtracker". The addressee(s) can be contacted for any purpose
including but not limited to (security) problems with the distribution,
questions about the distribution or bugs in the distribution.
A distribution's original author is usually the contact listed within
this field. Co-maintainers, successor maintainers or mailing lists
devoted to the distribution may also be listed in addition to or instead
of the original author.
_d_y_n_a_m_i_c___c_o_n_f_i_g
Example:
dynamic_config => 1
(Spec 2) [required] {Boolean}
A boolean flag indicating whether a _B_u_i_l_d_._P_L or _M_a_k_e_f_i_l_e_._P_L (or similar)
must be executed to determine prerequisites.
This field should be set to a true value if the distribution performs
some dynamic configuration (asking questions, sensing the environment,
etc.) as part of its configuration. This field should be set to a false
value to indicate that prerequisites included in metadata may be
considered final and valid for static analysis.
Note: when this field is true, post-configuration prerequisites are not
guaranteed to bear any relation whatsoever to those stated in the
metadata, and relying on them doing so is an error. See also
"Prerequisites for dynamically configured distributions" in the
implementors' notes.
This field explicitly ddooeess nnoott indicate whether installation may be
safely performed without using a Makefile or Build file, as there may be
special files to install or custom installation targets (e.g. for dual-
life modules that exist on CPAN as well as in the Perl core). This field
only defines whether or not prerequisites are exactly as given in the
metadata.
_g_e_n_e_r_a_t_e_d___b_y
Example:
generated_by => 'Module::Build version 0.36'
(Spec 1.0) [required] {String}
This field indicates the tool that was used to create this metadata.
There are no defined semantics for this field, but it is traditional to
use a string in the form "Generating::Package version 1.23" or the
author's name, if the file was generated by hand.
_l_i_c_e_n_s_e
Example:
license => [ 'perl_5' ]
license => [ 'apache_2_0', 'mozilla_1_0' ]
(Spec 2) [required] {List of one or more License Strings}
One or more licenses that apply to some or all of the files in the
distribution. If multiple licenses are listed, the distribution
documentation should be consulted to clarify the interpretation of
multiple licenses.
The following list of license strings are valid:
string description
------------- -----------------------------------------------
agpl_3 GNU Affero General Public License, Version 3
apache_1_1 Apache Software License, Version 1.1
apache_2_0 Apache License, Version 2.0
artistic_1 Artistic License, (Version 1)
artistic_2 Artistic License, Version 2.0
bsd BSD License (three-clause)
freebsd FreeBSD License (two-clause)
gfdl_1_2 GNU Free Documentation License, Version 1.2
gfdl_1_3 GNU Free Documentation License, Version 1.3
gpl_1 GNU General Public License, Version 1
gpl_2 GNU General Public License, Version 2
gpl_3 GNU General Public License, Version 3
lgpl_2_1 GNU Lesser General Public License, Version 2.1
lgpl_3_0 GNU Lesser General Public License, Version 3.0
mit MIT (aka X11) License
mozilla_1_0 Mozilla Public License, Version 1.0
mozilla_1_1 Mozilla Public License, Version 1.1
openssl OpenSSL License
perl_5 The Perl 5 License (Artistic 1 & GPL 1 or later)
qpl_1_0 Q Public License, Version 1.0
ssleay Original SSLeay License
sun Sun Internet Standards Source License (SISSL)
zlib zlib License
The following license strings are also valid and indicate other licensing
not described above:
string description
------------- -----------------------------------------------
open_source Other Open Source Initiative (OSI) approved license
restricted Requires special permission from copyright holder
unrestricted Not an OSI approved license, but not restricted
unknown License not provided in metadata
All other strings are invalid in the license field.
_m_e_t_a_-_s_p_e_c
Example:
'meta-spec' => {
version => '2',
url => 'http://search.cpan.org/perldoc?CPAN::Meta::Spec',
}
(Spec 1.2) [required] {Map}
This field indicates the version of the CPAN Meta Spec that should be
used to interpret the metadata. Consumers must check this key as soon as
possible and abort further metadata processing if the meta-spec version
is not supported by the consumer.
The following keys are valid, but only "version" is required.
version
This subkey gives the integer _V_e_r_s_i_o_n of the CPAN Meta Spec against
which the document was generated.
url This is a _U_R_L of the metadata specification document corresponding to
the given version. This is strictly for human-consumption and should
not impact the interpretation of the document.
For the version 2 spec, either of these are recommended:
• "https://metacpan.org/pod/CPAN::Meta::Spec"
• "http://search.cpan.org/perldoc?CPAN::Meta::Spec"
_n_a_m_e
Example:
name => 'Module-Build'
(Spec 1.0) [required] {String}
This field is the name of the distribution. This is often created by
taking the "main package" in the distribution and changing "::" to "-",
but the name may be completely unrelated to the packages within the
distribution. For example, LWP::UserAgent is distributed as part of the
distribution name "libwww-perl".
_r_e_l_e_a_s_e___s_t_a_t_u_s
Example:
release_status => 'stable'
(Spec 2) [required] {String}
This field provides the release status of this distribution. If the
"version" field contains an underscore character, then "release_status"
mmuusstt nnoott be "stable."
The "release_status" field mmuusstt have one of the following values:
stable
This indicates an ordinary, "final" release that should be indexed by
PAUSE or other indexers.
testing
This indicates a "beta" release that is substantially complete, but
has an elevated risk of bugs and requires additional testing. The
distribution should not be installed over a stable release without an
explicit request or other confirmation from a user. This release
status may also be used for "release candidate" versions of a
distribution.
unstable
This indicates an "alpha" release that is under active development,
but has been released for early feedback or testing and may be
missing features or may have serious bugs. The distribution should
not be installed over a stable release without an explicit request or
other confirmation from a user.
Consumers mmaayy use this field to determine how to index the distribution
for CPAN or other repositories in addition to or in replacement of
heuristics based on version number or file name.
_v_e_r_s_i_o_n
Example:
version => '0.36'
(Spec 1.0) [required] {Version}
This field gives the version of the distribution to which the metadata
structure refers.
OOPPTTIIOONNAALL FFIIEELLDDSS #
_d_e_s_c_r_i_p_t_i_o_n
Example:
description => "Module::Build is a system for "
. "building, testing, and installing Perl modules. "
. "It is meant to ... blah blah blah ...",
(Spec 2) [optional] {String}
A longer, more complete description of the purpose or intended use of the
distribution than the one provided by the "abstract" key.
_k_e_y_w_o_r_d_s
Example:
keywords => [ qw/ toolchain cpan dual-life / ]
(Spec 1.1) [optional] {List of zero or more Strings}
A List of keywords that describe this distribution. Keywords mmuusstt nnoott
include whitespace.
_n_o___i_n_d_e_x
Example:
no_index => {
file => [ 'My/Module.pm' ],
directory => [ 'My/Private' ],
package => [ 'My::Module::Secret' ],
namespace => [ 'My::Module::Sample' ],
}
(Spec 1.2) [optional] {Map}
This Map describes any files, directories, packages, and namespaces that
are private to the packaging or implementation of the distribution and
should be ignored by indexing or search tools. Note that this is a list
of exclusions, and the spec does not define what to _i_n_c_l_u_d_e - see
"Indexing distributions a la PAUSE" in the implementors notes for more
information.
Valid subkeys are as follows:
file
A _L_i_s_t of relative paths to files. Paths mmuusstt bbee specified with unix
conventions.
directory
A _L_i_s_t of relative paths to directories. Paths mmuusstt bbee specified
with unix conventions.
[ Note: previous editions of the spec had "dir" instead of
"directory" ]
package
A _L_i_s_t of package names.
namespace
A _L_i_s_t of package namespaces, where anything below the namespace must
be ignored, but _n_o_t the namespace itself.
In the example above for "no_index", "My::Module::Sample::Foo" would
be ignored, but "My::Module::Sample" would not.
_o_p_t_i_o_n_a_l___f_e_a_t_u_r_e_s
Example:
optional_features => {
sqlite => {
description => 'Provides SQLite support',
prereqs => {
runtime => {
requires => {
'DBD::SQLite' => '1.25'
}
}
}
}
}
(Spec 2) [optional] {Map}
This Map describes optional features with incremental prerequisites.
Each key of the "optional_features" Map is a String used to identify the
feature and each value is a Map with additional information about the
feature. Valid subkeys include:
description
This is a String describing the feature. Every optional feature
should provide a description
prereqs
This entry is required and has the same structure as that of the
"prereqs" key. It provides a list of package requirements that must
be satisfied for the feature to be supported or enabled.
There is one crucial restriction: the prereqs of an optional feature
mmuusstt nnoott include "configure" phase prereqs.
Consumers mmuusstt nnoott include optional features as prerequisites without
explicit instruction from users (whether via interactive prompting, a
function parameter or a configuration value, etc. ).
If an optional feature is used by a consumer to add additional
prerequisites, the consumer should merge the optional feature
prerequisites into those given by the "prereqs" key using the same
semantics. See "Merging and Resolving Prerequisites" for details on
merging prerequisites.
_S_u_g_g_e_s_t_i_o_n _f_o_r _d_i_s_u_s_e_: Because there is currently no way for a
distribution to specify a dependency on an optional feature of another
dependency, the use of "optional_feature" is discouraged. Instead,
create a separate, installable distribution that ensures the desired
feature is available. For example, if "Foo::Bar" has a "Baz" feature,
release a separate "Foo-Bar-Baz" distribution that satisfies requirements
for the feature.
_p_r_e_r_e_q_s
Example:
prereqs => {
runtime => {
requires => {
'perl' => '5.006',
'File::Spec' => '0.86',
‘JSON’ => ‘2.16’, #
},
recommends => {
‘JSON::XS’ => ‘2.26’, #
},
suggests => {
'Archive::Tar' => '0',
},
},
build => {
requires => {
'Alien::SDL' => '1.00',
},
},
test => {
recommends => {
'Test::Deep' => '0.10',
},
}
}
(Spec 2) [optional] {Map}
This is a Map that describes all the prerequisites of the distribution.
The keys are phases of activity, such as "configure", "build", "test" or
"runtime". Values are Maps in which the keys name the type of
prerequisite relationship such as "requires", "recommends", or "suggests"
and the value provides a set of prerequisite relations. The set of
relations mmuusstt be specified as a Map of package names to version ranges.
The full definition for this field is given in the "Prereq Spec" section.
_p_r_o_v_i_d_e_s
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 1.2) [optional] {Map}
This describes all packages provided by this distribution. This
information is used by distribution and automation mechanisms like PAUSE,
CPAN, metacpan.org and search.cpan.org to build indexes saying in which
distribution various packages can be found.
The keys of "provides" are package names that can be found within the
distribution. If a package name key is provided, it must have a Map with
the following valid subkeys:
file
This field is required. It must contain a Unix-style relative file
path from the root of the distribution directory to a file that
contains or generates the package. It may be given as "META.yml" or
"META.json" to claim a package for indexing without needing a "*.pm".
version
If it exists, this field must contains a _V_e_r_s_i_o_n String for the
package. If the package does not have a $VERSION, this field must be
omitted.
_r_e_s_o_u_r_c_e_s
Example:
resources => {
license => [ 'http://dev.perl.org/licenses/' ],
homepage => 'http://sourceforge.net/projects/module-build',
bugtracker => {
web => 'http://rt.cpan.org/Public/Dist/Display.html?Name=CPAN-Meta',
mailto => 'meta-bugs@example.com',
},
repository => {
url => 'git://github.com/dagolden/cpan-meta.git',
web => 'http://github.com/dagolden/cpan-meta',
type => 'git',
},
x_twitter => 'http://twitter.com/cpan_linked/',
}
(Spec 2) [optional] {Map}
This field describes resources related to this distribution.
Valid subkeys include:
homepage
The official home of this project on the web.
license
A List of _U_R_L's that relate to this distribution's license. As with
the top-level "license" field, distribution documentation should be
consulted to clarify the interpretation of multiple licenses provided
here.
bugtracker
This entry describes the bug tracking system for this distribution.
It is a Map with the following valid keys:
web - a URL pointing to a web front-end for the bug tracker
mailto - an email address to which bugs can be sent
repository
This entry describes the source control repository for this
distribution. It is a Map with the following valid keys:
url - a URL pointing to the repository itself
web - a URL pointing to a web front-end for the repository
type - a lowercase string indicating the VCS used
Because a url like "http://myrepo.example.com/" is ambiguous as to
type, producers should provide a "type" whenever a "url" key is
given. The "type" field should be the name of the most common
program used to work with the repository, e.g. "git", "svn", "cvs",
"darcs", "bzr" or "hg".
DDEEPPRREECCAATTEEDD FFIIEELLDDSS #
_b_u_i_l_d___r_e_q_u_i_r_e_s
_(_D_e_p_r_e_c_a_t_e_d _i_n _S_p_e_c _2_) [optional] {String}
Replaced by "prereqs"
_c_o_n_f_i_g_u_r_e___r_e_q_u_i_r_e_s
_(_D_e_p_r_e_c_a_t_e_d _i_n _S_p_e_c _2_) [optional] {String}
Replaced by "prereqs"
_c_o_n_f_l_i_c_t_s
_(_D_e_p_r_e_c_a_t_e_d _i_n _S_p_e_c _2_) [optional] {String}
Replaced by "prereqs"
_d_i_s_t_r_i_b_u_t_i_o_n___t_y_p_e
_(_D_e_p_r_e_c_a_t_e_d _i_n _S_p_e_c _2_) [optional] {String}
This field indicated 'module' or 'script' but was considered meaningless,
since many distributions are hybrids of several kinds of things.
_l_i_c_e_n_s_e___u_r_i
_(_D_e_p_r_e_c_a_t_e_d _i_n _S_p_e_c _1_._2_) [optional] {URL}
Replaced by "license" in "resources"
_p_r_i_v_a_t_e
_(_D_e_p_r_e_c_a_t_e_d _i_n _S_p_e_c _1_._2_) [optional] {Map}
This field has been renamed to "no_index".
_r_e_c_o_m_m_e_n_d_s
_(_D_e_p_r_e_c_a_t_e_d _i_n _S_p_e_c _2_) [optional] {String}
Replaced by "prereqs"
_r_e_q_u_i_r_e_s
_(_D_e_p_r_e_c_a_t_e_d _i_n _S_p_e_c _2_) [optional] {String}
Replaced by "prereqs"
VVEERRSSIIOONN NNUUMMBBEERRSS #
VVeerrssiioonn FFoorrmmaattss This section defines the Version type, used by several fields in the CPAN Meta Spec.
Version numbers must be treated as strings, not numbers. For example,
1.200 mmuusstt nnoott be serialized as 1.2. Version comparison should be
delegated to the Perl version module, version 0.80 or newer.
Unless otherwise specified, version numbers mmuusstt appear in one of two
formats:
Decimal versions
Decimal versions are regular "decimal numbers", with some
limitations. They mmuusstt be non-negative and mmuusstt begin and end with a
digit. A single underscore mmaayy be included, but mmuusstt be between two
digits. They mmuusstt nnoott use exponential notation ("1.23e-2").
version => '1.234' # OK
version => '1.23_04' # OK
version => '1.23_04_05' # Illegal
version => '1.' # Illegal
version => '.1' # Illegal
Dotted-integer versions
Dotted-integer (also known as dotted-decimal) versions consist of
positive integers separated by full stop characters (i.e. "dots",
"periods" or "decimal points"). This are equivalent in format to
Perl "v-strings", with some additional restrictions on form. They
must be given in "normal" form, which has a leading "v" character and
at least three integer components. To retain a one-to-one mapping
with decimal versions, all components after the first sshhoouulldd be
restricted to the range 0 to 999. The final component mmaayy be
separated by an underscore character instead of a period.
version => 'v1.2.3' # OK
version => 'v1.2_3' # OK
version => 'v1.2.3.4' # OK
version => 'v1.2.3_4' # OK
version => 'v2009.10.31' # OK
version => 'v1.2' # Illegal
version => '1.2.3' # Illegal
version => 'v1.2_3_4' # Illegal
version => 'v1.2009.10.31' # Not recommended
VVeerrssiioonn RRaannggeess Some fields (prereq, optional_features) indicate the particular version(s) of some other module that may be required as a prerequisite. This section details the Version Range type used to provide this information.
The simplest format for a Version Range is just the version number
itself, e.g. 2.4. This means that aatt lleeaasstt version 2.4 must be present.
To indicate that aannyy version of a prerequisite is okay, even if the
prerequisite doesn't define a version at all, use the version 0.
Alternatively, a version range mmaayy use the operators < (less than), <=
(less than or equal), > (greater than), >= (greater than or equal), ==
(equal), and != (not equal). 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 mmaayy be AND-ed
together using commas. The specification ">= 1.2, != 1.5, < 2.0"
indicates a version that must be aatt lleeaasstt 1.2, lleessss tthhaann 2.0, and nnoott
eeqquuaall ttoo 1.5.
PPRREERREEQQUUIISSIITTEESS #
PPrreerreeqq SSppeecc The “prereqs” key in the top-level metadata and within “optional_features” define the relationship between a distribution and other packages. The prereq spec structure is a hierarchical data structure which divides prerequisites into _P_h_a_s_e_s of activity in the installation process and _R_e_l_a_t_i_o_n_s_h_i_p_s that indicate how prerequisites should be resolved.
For example, to specify that "Data::Dumper" is "required" during the
"test" phase, this entry would appear in the distribution metadata:
prereqs => {
test => {
requires => {
'Data::Dumper' => '2.00'
}
}
}
_P_h_a_s_e_s
Requirements for regular use must be listed in the "runtime" phase.
Other requirements should be listed in the earliest stage in which they
are required and consumers must accumulate and satisfy requirements
across phases before executing the activity. For example, "build"
requirements must also be available during the "test" phase.
before action requirements that must be met
---------------- --------------------------------
perl Build.PL configure
perl Makefile.PL
make configure, runtime, build
Build
make test configure, runtime, build, test
Build test
Consumers that install the distribution must ensure that _r_u_n_t_i_m_e
requirements are also installed and may install dependencies from other
phases.
after action requirements that must be met
---------------- --------------------------------
make install runtime
Build install
configure
The configure phase occurs before any dynamic configuration has been
attempted. Libraries required by the configure phase mmuusstt be
available for use before the distribution building tool has been
executed.
build
The build phase is when the distribution's source code is compiled
(if necessary) and otherwise made ready for installation.
test
The test phase is when the distribution's automated test suite is
run. Any library that is needed only for testing and not for
subsequent use should be listed here.
runtime
The runtime phase refers not only to when the distribution's contents
are installed, but also to its continued use. Any library that is a
prerequisite for regular use of this distribution should be indicated
here.
develop
The develop phase's prereqs are libraries needed to work on the
distribution's source code as its author does. These tools might be
needed to build a release tarball, to run author-only tests, or to
perform other tasks related to developing new versions of the
distribution.
_R_e_l_a_t_i_o_n_s_h_i_p_s
requires
These dependencies mmuusstt be installed for proper completion of the
phase.
recommends
Recommended dependencies are _s_t_r_o_n_g_l_y encouraged and should be
satisfied except in resource constrained environments.
suggests
These dependencies are optional, but are suggested for enhanced
operation of the described distribution.
conflicts
These libraries cannot be installed when the phase is in operation.
This is a very rare situation, and the "conflicts" relationship
should be used with great caution, or not at all.
MMeerrggiinngg aanndd RReessoollvviinngg PPrreerreeqquuiissiitteess Whenever metadata consumers merge prerequisites, either from different phases or from “optional_features”, they should merged in a way which preserves the intended semantics of the prerequisite structure. Generally, this means concatenating the version specifications using commas, as described in the “Version Ranges” section.
Another subtle error that can occur in resolving prerequisites comes from
the way that modules in prerequisites are indexed to distribution files
on CPAN. When a module is deleted from a distribution, prerequisites
calling for that module could indicate an older distribution should be
installed, potentially overwriting files from a newer distribution.
For example, as of Oct 31, 2009, the CPAN index file contained these
module-distribution mappings:
Class::MOP 0.94 D/DR/DROLSKY/Class-MOP-0.94.tar.gz
Class::MOP::Class 0.94 D/DR/DROLSKY/Class-MOP-0.94.tar.gz
Class::MOP::Class::Immutable 0.04 S/ST/STEVAN/Class-MOP-0.36.tar.gz
Consider the case where "Class::MOP" 0.94 is installed. If a
distribution specified "Class::MOP::Class::Immutable" as a prerequisite,
it could result in Class-MOP-0.36.tar.gz being installed, overwriting any
files from Class-MOP-0.94.tar.gz.
Consumers of metadata sshhoouulldd test whether prerequisites would result in
installed module files being "downgraded" to an older version and mmaayy
warn users or ignore the prerequisite that would cause such a result.
SSEERRIIAALLIIZZAATTIIOONN #
Distribution metadata should be serialized (as a hashref) as JSON-encoded
data and packaged with distributions as the file _M_E_T_A_._j_s_o_n.
In the past, the distribution metadata structure had been packed with
distributions as _M_E_T_A_._y_m_l, a file in the YAML Tiny format (for which, see
YAML::Tiny). Tools that consume distribution metadata from disk should
be capable of loading _M_E_T_A_._y_m_l, but should prefer _M_E_T_A_._j_s_o_n if both are
found.
NNOOTTEESS FFOORR IIMMPPLLEEMMEENNTTOORRSS #
EExxttrraaccttiinngg VVeerrssiioonn NNuummbbeerrss ffrroomm PPeerrll MMoodduulleess To get the version number from a Perl module, consumers should use the “MM->parse_version($file)” method provided by ExtUtils::MakeMaker or Module::Metadata. For example, for the module given by $mod, the version may be retrieved in one of the following ways:
# via ExtUtils::MakeMaker
my $file = MM->_installed_file_for_module($mod);
my $version = MM->parse_version($file)
The private "_installed_file_for_module" method may be replaced with
other methods for locating a module in @INC.
# via Module::Metadata
my $info = Module::Metadata->new_from_module($mod);
my $version = $info->version;
If only a filename is available, the following approach may be used:
# via Module::Build
my $info = Module::Metadata->new_from_file($file);
my $version = $info->version;
CCoommppaarriinngg VVeerrssiioonn NNuummbbeerrss The version module provides the most reliable way to compare version numbers in all the various ways they might be provided or might exist within modules. Given two strings containing version numbers, $v1 and $v2, they should be converted to “version” objects before using ordinary comparison operators. For example:
use version;
if ( version->new($v1) <=> version->new($v2) ) {
print "Versions are not equal\n";
}
If the only comparison needed is whether an installed module is of a
sufficiently high version, a direct test may be done using the string
form of "eval" and the "use" function. For example, for module $mod and
version prerequisite $prereq:
if ( eval "use $mod $prereq (); 1" ) {
print "Module $mod version is OK.\n";
}
If the values of $mod and $prereq have not been scrubbed, however, this
presents security implications.
PPrreerreeqquuiissiitteess ffoorr ddyynnaammiiccaallllyy ccoonnffiigguurreedd ddiissttrriibbuuttiioonnss When “dynamic_config” is true, it is an error to presume that the prerequisites given in distribution metadata will have any relationship whatsoever to the actual prerequisites of the distribution.
In practice, however, one can generally expect such prerequisites to be
one of two things:
• The minimum prerequisites for the distribution, to which dynamic
configuration will only add items
• Whatever the distribution configured with on the releaser's machine
at release time
The second case often turns out to have identical results to the first
case, albeit only by accident.
As such, consumers may use this data for informational analysis, but
presenting it to the user as canonical or relying on it as such is
invariably the height of folly.
IInnddeexxiinngg ddiissttrriibbuuttiioonnss aa llaa PPAAUUSSEE While no_index tells you what must be ignored when indexing, this spec holds no opinion on how you should get your initial candidate list of things to possibly index. For “normal” distributions you might consider simply indexing the contents of lib/, but there are many fascinating oddities on CPAN and many dists from the days when it was normal to put the main .pm file in the root of the distribution archive - so PAUSE currently indexes all .pm and .PL files that are not either (a) specifically excluded by no_index (b) in “inc”, “xt”, or “t” directories, or common ‘mistake’ directories such as “perl5”.
Or: If you're trying to be PAUSE-like, make sure you skip "inc", "xt" and
"t" as well as anything marked as no_index.
Also remember: If the META file contains a provides field, you shouldn't
be indexing anything in the first place - just use that.
SSEEEE AALLSSOO #
• CPAN, <http://www.cpan.org/>
• JSON, <http://json.org/>
• YAML, <http://www.yaml.org/>
• CPAN #
• CPANPLUS #
• ExtUtils::MakeMaker
• Module::Build
• Module::Install
• CPAN::Meta::History::Meta_1_4
HHIISSTTOORRYY #
Ken Williams wrote the original CPAN Meta Spec (also known as the
"META.yml spec") in 2003 and maintained it through several revisions with
input from various members of the community. In 2005, Randy Sims
redrafted it from HTML to POD for the version 1.2 release. Ken continued
to maintain the spec through version 1.4.
In late 2009, David Golden organized the version 2 proposal review
process. David and Ricardo Signes drafted the final version 2 spec in
April 2010 based on the version 1.4 spec and patches contributed during
the proposal process.
AAUUTTHHOORRSS #
• David Golden <dagolden@cpan.org>
• Ricardo Signes <rjbs@cpan.org>
• Adam Kennedy <adamk@cpan.org>
CCOOPPYYRRIIGGHHTT AANNDD LLIICCEENNSSEE #
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 v5.36.3 2019-02-13 CPAN::Meta::Spec(3p)