Add a little bit on handling of broken behavior that cannot be deprecated.

[gitmo/Moose.git] / lib / Moose / Manual / Support.pod

=pod

=head1 NAME

Moose::Manual::Support - Policies regarding support, releases, and
compatibility.

=head1 SUPPORT POLICY

There are two principles to Moose's policy of supported behavior.

=over 4

=item 1.

Moose favors correctness over everything.

=item 2.

Moose supports documented and tested behavior, not accidental behavior or side
effects.

=back

If a behavior has never been documented or tested, the behavior is
I<officially> undefined. Relying upon undocumented and untested behavior is
done at your own risk.

If a behavior is documented or tested but found to be incorrect later, the
behavior will go through a deprecation period. During the deprecation period,
use of that feature will cause a warning. Eventually, the deprecated feature
will be removed.

In some cases, it is not possible to deprecate a behavior. In this case, the
behavior will simply be changed in a major release.

=head1 RELEASE SCHEDULE

Moose is on a system of quarterly major releases, with minor releases as
needed between major releases. A minor release is defined as one that makes
every attempt to preserve backwards compatibility. Currently this means that we
did not introduce any new dependency conflicts, and that we did not make any
changes to documented or tested behavior (this typically means that minor
releases will not change any existing tests in the test suite, although they
can add new ones). A minor release can include new features and bug fixes.

Major releases may be backwards incompatible. Moose prioritizes
correctness over backwards compatibility or performance; see the L<Deprecation
Policy> to understand how backwards incompatible changes are announced.

Major releases are scheduled to happen during fixed release windows. If the
window is missed, then there will not be a major release until the next
release window. The release windows are one month long, and occur during the
months of January, April, July, and October.

Before a major release, a series of development releases will be made so that
users can test the upcoming major release before it is distributed to CPAN. It
is in the best interests of everyone involved if these releases are tested as
widely as possible.

=head1 DEPRECATION POLICY

Moose has always prioritized correctness over performance and backwards
compatibility.

Major deprecations or API changes are documented in the Changes file as well
as in L<Moose::Manual::Delta>. The Moose developers will also make an effort
to warn users of upcoming deprecations and breakage through the Moose blog
(http://blog.moose.perl.org).

Deprecated APIs will be preserved for at least one year I<after the major
release which deprecates that API>. Deprecated APIs will only be removed in a
major release.

Moose will also warn during installation if the version of Moose being
installed will break an installed dependency. Unfortunately, due to the nature
of the Perl install process these warnings may be easy to miss.

=head1 BACKWARDS COMPATIBILITY

We try to ensure compatibility by having a extensive test suite (last
count just over around 5123 tests), as well as testing a number of
packages (currently just under 100 packages) that depend on Moose before
any release.

The current list of downstream dependencies that are tested is in
C<xt/author/test-my-dependents.t>.

=head1 VERSION NUMBERS

Moose version numbers consist of three parts, in the form X.YYZZ. The X is the
"special magic number" that only gets changed for really big changes. Think of
this as being like the "5" in Perl 5.12.1.

The YY portion is the major version number. Moose uses even numbers for stable
releases, and odd numbers for trial releases. The ZZ is the minor version, and
it simply increases monotonically. It starts at "00" each time a new major
version is released.

Semantically, this means that any two releases which share a major version
should be API-compatible with each other. In other words, 2.0200, 2.0201, and
2.0274 are all API-compatible.

Prior to version 2.0, Moose version numbers were monotonically incrementing
two decimal values (0.01, 0.02, ... 1.11, 1.12, etc.).

Moose was declared production ready at version 0.18 (via L<<
http://www.perlmonks.org/?node_id=608144 >>).

=head1 PERL VERSION COMPATIBILITY

As of version 2.00, Moose officially supports being run on perl 5.8.3+. Our
current policy is to support the earliest version of Perl shipped in the latest
stable release of any major operating system (this tends to mean CentOS). We
will provide at least six months notice (two major releases) when we decide to
increase the officially supported Perl version. The next time this will happen
is in January of 2012, when Moose 2.06 will increase the minimum officially
supported Perl version to 5.10.1.

"Officially supported" does not mean that these are the only versions of Perl
that Moose will work with. Our declared perl dependency will remain at 5.8.3 as
long as our test suite continues to pass on 5.8.3. What this does mean is that
the core Moose dev team will not be spending any time fixing bugs on versions
that aren't officially supported, and new contributions will not be rejected
due to being incompatible with older versions of perl except in the most
trivial of cases. We will, however, still welcome patches to make Moose
compatible with earlier versions, if other people are still interested in
maintaining compatibility. Note that although performance regressions are
acceptable in order to maintain backwards compatibility (as long as they only
affect the older versions), functionality changes and buggy behavior will not
be. If it becomes impossible to provide identical functionality between modern
Perl versions and unsupported Perl versions, we will increase our declared perl
dependency instead.

=head1 CONTRIBUTING

Moose has an open contribution policy. Anybody is welcome to submit a
patch. Please see L<Moose::Manual::Contributing> for more details.

=cut