Document no "+foo" for role attrs, and related composition_class_roles change

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

=pod

=head1 NAME

Moose::Manual::Delta - Important Changes in Moose

=head1 DESCRIPTION

This documents any important or noteworthy changes in Moose, with a
focus on backwards. This does duplicate data from the F<Changes> file,
but aims to provide more details and when possible workarounds.

Besides helping keep up with changes, you can also use this document
for finding the lowest version of Moose that supported a given
feature.  If you encounter a problem and have a solution but don't see
it documented here, or think we missed an important feature, please
send us a patch.

=head1 0.93_01 and 0.94

=over 4

=item "no Moose" now removes C<blessed> and C<confess>

Moose is now smart enough to know exactly what it exported, even when it
re-exports functions from other packages. When you unimport Moose, it will
remove these functions from your namespace unless you I<also> imported them
directly from their respective packages.

If you have a C<no Moose> in your code I<before> you call C<blessed> or
C<confess>, your code will break. You can either move the C<no Moose> call
later in your code, or explicitly import the relevant functions from the
packages that provide them.

=item L<Moose::Exporter> is smarter about unimporting re-exports

The change above comes from a general improvement to L<Moose::Exporter>. It
will now unimport any function it exports, even if that function is a
re-export from another package.

=item Attributes in roles can no longer override class attributes with "+foo"

Previously, this worked more or less accidentally, because role attributes
weren't objects. This was never documented, but a few MooseX modules took
advantage of this.

=item The composition_class_roles attribute in L<Moose::Meta::Role> is now a method

This was done to make it possible for roles to alter the the list of
composition class roles by applying a method modifiers. Previously, this was
an attribute and MooseX modules override it. Since that no longer works, this
was made a method.

This I<should> be an attribute, so this may switch back to being an attribute
in the future if we can figure out how to make this work.

=back

=head1 0.93

=over 4

=item Calling $object->new() is no longer deprecated

We decided to undeprecate this. Now it just works.

=item Both C<get_method_map> and C<get_attribute_map> is deprecated

These metaclass methods were never meant to be public, and they are both now
deprecated. The work around if you still need the functionality they provided
is to iterate over the list of names manually.

    my %fields = map { $_ => $meta->get_attribute($_) } $meta->get_attribute_list;

This was actually a change in L<Class::MOP>, but this version of Moose
requires a version of L<Class::MOP> that includes said change.

=back

=head1 0.90

=over 4

=item Added Native delegation for Code refs

See L<Moose::Meta::Attribute::Native::Trait::Code> for details.

=item Calling $object->new() is deprecated

Moose has long supported this, but it's never really been documented, and we
don't think this is a good practice. If you want to construct an object from
an existing object, you should provide some sort of alternate constructor like
C<< $object->clone >>.

Calling C<< $object->new >> now issues a warning, and will be an error in a
future release.

=item Moose no longer warns if you call C<make_immutable> for a class with mutable ancestors

While in theory this is a good thing to warn about, we found so many
exceptions to this that doing this properly became quite problematic.

=back

=head1 Version 0.89_02

=over 4

=item New Native delegation methods from L<List::Util> and L<List::MoreUtils>

In particular, we now have C<reduce>, C<shuffle>, C<uniq>, and C<natatime>.

=item The Moose::Exporter with_caller feature is now deprecated

Use C<with_meta> instead. The C<with_caller> option will start warning in a
future release.

=item Moose now warns if you call C<make_immutable> for a class with mutable ancestors

This is dangerous because modifying a class after a subclass has been
immutabilized will lead to incorrect results in the subclass, due to inlining,
caching, etc. This occasionally happens accidentally, when a class loads one
of its subclasses in the middle of its class definition, so pointing out that
this may cause issues should be helpful. Metaclasses (classes that inherit
from L<Class::MOP::Object>) are currently exempt from this check, since at the
moment we aren't very consistent about which metaclasses we immutabilize.

=item C<enum> and C<duck_type> now take arrayrefs for all forms

Previously, calling these functions with a list would take the first element of
the list as the type constraint name, and use the remainder as the enum values
or method names. This makes the interface inconsistent with the anon-type forms
of these functions (which must take an arrayref), and a free-form list where
the first value is sometimes special is hard to validate (and harder to give
reasonable error messages for). These functions have been changed to take
arrayrefs in all their forms - so, C<< enum 'My::Type' => [qw(foo bar)] >> is
now the preferred way to create an enum type constraint. The old syntax still
works for now, but it will hopefully be deprecated and removed in a future
release.

=back

=head1 Version 0.89_01

L<Moose::Meta::Attribute::Native> has been moved into the Moose core from
L<MooseX::AttributeHelpers>.  Major changes include:

=over 4

=item C<traits>, not C<metaclass>

Method providers are only available via traits.

=item C<handles>, not C<provides> or C<curries>

The C<provides> syntax was like core Moose C<< handles => HASHREF >>
syntax, but with the keys and values reversed.  This was confusing,
and AttributeHelpers now uses C<< handles => HASHREF >> in a way that
should be intuitive to anyone already familiar with how it is used for
other attributes.

The C<curries> functionality provided by AttributeHelpers has been
generalized to apply to all cases of C<< handles => HASHREF >>, though
not every piece of functionality has been ported (currying with a
CODEREF is not supported).

=item C<empty> is now C<is_empty>, and means empty, not non-empty

Previously, the C<empty> method provided by Arrays and Hashes returned true if
the attribute was B<not> empty (no elements).  Now it returns true if the
attribute B<is> empty. It was also renamed to C<is_empty>, to reflect this.

=item C<find> was renamed to C<first>, and C<first> and C<last> were removed

L<List::Util> refers to the functionality that we used to provide under C<find>
as L<first|List::Util/first>, so that will likely be more familiar (and will
fit in better if we decide to add more List::Util functions). C<first> and
C<last> were removed, since their functionality is easily duplicated with
curries of C<get>.

=item Helpers that take a coderef of one argument now use C<$_>

Subroutines passed as the first argument to C<first>, C<map>, and C<grep> now
receive their argument in C<$_> rather than as a parameter to the subroutine.
Helpers that take a coderef of two or more arguments remain using the argument
list (there are technical limitations to using C<$a> and C<$b> like C<sort>
does).

See L<Moose::Meta::Attribute::Native> for the new documentation.

=back

The C<alias> and C<excludes> role parameters have been renamed to C<-alias>
and C<-excludes>. The old names still work, but new code should use the new
names, and eventually the old ones will be deprecated and removed.

=head1 Version 0.89

C<< use Moose -metaclass => 'Foo' >> now does alias resolution, just like
C<-traits> (and the C<metaclass> and C<traits> options to C<has>).

Added two functions C<meta_class_alias> and C<meta_attribute_alias> to
L<Moose::Util>, to simplify aliasing metaclasses and metatraits. This is
a wrapper around the old

  package Moose::Meta::Class::Custom::Trait::FooTrait;
  sub register_implementation { 'My::Meta::Trait' }

way of doing this.

=head1 Version 0.84

When an attribute generates I<no> accessors, we now warn. This is to help
users who forget the C<is> option. If you really do not want any accessors,
you can use C<< is => 'bare' >>. You can maintain back compat with older
versions of Moose by using something like:

    ($Moose::VERSION >= 0.84 ? is => 'bare' : ())

When an accessor overwrites an existing method, we now warn. To work around
this warning (if you really must have this behavior), you can explicitly
remove the method before creating it as an accessor:

    sub foo {}

    __PACKAGE__->meta->remove_method('foo');

    has foo => (
        is => 'ro',
    );

When an unknown option is passed to C<has>, we now warn. You can silence
the warning by fixing your code. :)

The C<Role> type has been deprecated. On its own, it was useless,
since it just checked C<< $object->can('does') >>. If you were using
it as a parent type, just call C<role_type('Role::Name')> to create an
appropriate type instead.

=head1 Version 0.78

C<use Moose::Exporter;> now imports C<strict> and C<warnings> into packages
that use it.

=head1 Version 0.77

C<DEMOLISHALL> and C<DEMOLISH> now receive an argument indicating whether or
not we are in global destruction.

=head1 Version 0.76

Type constraints no longer run coercions for a value that already matches the
constraint.  This may affect some (arguably buggy) edge case coercions that
rely on side effects in the C<via> clause.

=head1 Version 0.75

L<Moose::Exporter> now accepts the C<-metaclass> option for easily
overriding the metaclass (without L<metaclass>). This works for classes
and roles.

=head1 Version 0.74

Added a C<duck_type> sugar function to L<Moose::Util::TypeConstraints>
to make integration with non-Moose classes easier. It simply checks if
C<< $obj->can() >> a list of methods.

A number of methods (mostly inherited from L<Class::MOP>) have been
renamed with a leading underscore to indicate their internal-ness. The
old method names will still work for a while, but will warn that the
method has been renamed. In a few cases, the method will be removed
entirely in the future. This may affect MooseX authors who were using
these methods.

=head1 Version 0.73

Calling C<subtype> with a name as the only argument now throws an
exception. If you want an anonymous subtype do:

    my $subtype = subtype as 'Foo';

This is related to the changes in version 0.71_01.

The C<is_needed> method in L<Moose::Meta::Method::Destructor> is now
only usable as a class method. Previously, it worked as a class or
object method, with a different internal implementation for each
version.

The internals of making a class immutable changed a lot in Class::MOP
0.78_02, and Moose's internals have changed along with it. The
external C<< $metaclass->make_immutable >> method still works the same
way.

=head1 Version 0.72

A mutable class accepted C<< Foo->new(undef) >> without complaint,
while an immutable class would blow up with an unhelpful error. Now,
in both cases we throw a helpful error instead.

This "feature" was originally added to allow for cases such as this:

  my $args;

  if ( something() ) {
      $args = {...};
  }

  return My::Class->new($args);

But we decided this is a bad idea and a little too magical, because it
can easily mask real errors.

=head1 Version 0.71_01

Calling C<type> or C<subtype> without the sugar helpers (C<as>,
C<where>, C<message>) is now deprecated.

As a side effect, this meant we ended up using Perl prototypes on
C<as>, and code like this will no longer work:

  use Moose::Util::TypeConstraints;
  use Declare::Constraints::Simple -All;

  subtype 'ArrayOfInts'
      => as 'ArrayRef'
      => IsArrayRef(IsInt);

Instead it must be changed to this:

  subtype(
      'ArrayOfInts' => {
          as    => 'ArrayRef',
          where => IsArrayRef(IsInt)
      }
  );

If you want to maintain backwards compat with older versions of Moose,
you must explicitly test Moose's C<VERSION>:

  if ( Moose->VERSION < 0.71_01 ) {
      subtype 'ArrayOfInts'
          => as 'ArrayRef'
          => IsArrayRef(IsInt);
  }
  else {
      subtype(
          'ArrayOfInts' => {
              as    => 'ArrayRef',
              where => IsArrayRef(IsInt)
          }
      );
  }

=head1 Version 0.70

We no longer pass the meta-attribute object as a final argument to
triggers. This actually changed for inlined code a while back, but the
non-inlined version and the docs were still out of date.

If by some chance you actually used this feature, the workaround is
simple. You fetch the attribute object from out of the C<$self>
that is passed as the first argument to trigger, like so:

  has 'foo' => (
      is      => 'ro',
      isa     => 'Any',
      trigger => sub {
          my ( $self, $value ) = @_;
          my $attr = $self->meta->find_attribute_by_name('foo');

          # ...
      }
  );

=head1 Version 0.66

If you created a subtype and passed a parent that Moose didn't know
about, it simply ignored the parent. Now it automatically creates the
parent as a class type. This may not be what you want, but is less
broken than before.

You could declare a name with subtype such as "Foo!Bar". Moose would
accept this allowed, but if you used it in a parameterized type such
as "ArrayRef[Foo!Bar]" it wouldn't work. We now do some vetting on
names created via the sugar functions, so that they can only contain
alphanumerics, ":", and ".".

=head1 Version 0.65

Methods created via an attribute can now fulfill a C<requires>
declaration for a role. Honestly we don't know why Stevan didn't make
this work originally, he was just insane or something.

Stack traces from inlined code will now report the line and file as
being in your class, as opposed to in Moose guts.

=head1 Version 0.62_02

When a class does not provide all of a role's required methods, the
error thrown now mentions all of the missing methods, as opposed to
just the first missing method.

Moose will no longer inline a constructor for your class unless it
inherits its constructor from Moose::Object, and will warn when it
doesn't inline. If you want to force inlining anyway, pass
C<< replace_constructor => 1 >> to C<make_immutable>.

If you want to get rid of the warning, pass C<< inline_constructor =>
0 >>.

=head1 Version 0.62

Removed the (deprecated) C<make_immutable> keyword.

Removing an attribute from a class now also removes delegation
(C<handles>) methods installed for that attribute. This is correct
behavior, but if you were wrongly relying on it you might get bit.

=head1 Version 0.58

Roles now add methods by calling C<add_method>, not
C<alias_method>. They make sure to always provide a method object,
which will be cloned internally. This means that it is now possible to
track the source of a method provided by a role, and even follow its
history through intermediate roles.  This means that methods added by
a role now show up when looking at a class's method list/map.

Parameter and Union args are now sorted, this makes Int|Str the same
constraint as Str|Int. Also, incoming type constraint strings are
normalized to remove all whitespace differences. This is mostly for
internals and should not affect outside code.

L<Moose::Exporter> will no longer remove a subroutine that the
exporting package re-exports. Moose re-exports the Carp::confess
function, among others. The reasoning is that we cannot know whether
you have also explicitly imported those functions for your own use, so
we err on the safe side and always keep them.

=head1 Version 0.56

C<Moose::init_meta> should now be called as a method.

New modules for extension writers, L<Moose::Exporter> and
L<Moose::Util::MetaRole>.

=head1 Version 0.55_01

Implemented metaclass traits (and wrote a recipe for it):

  use Moose -traits => 'Foo'

This should make writing small Moose extensions a little
easier.

=head1 Version 0.55

Fixed C<coerce> to accept anon types just like C<subtype> can.
So that you can do:

  coerce $some_anon_type => from 'Str' => via { ... };

=head1 Version 0.51

Added C<BUILDARGS>, a new step in C<< Moose::Object->new() >>.

=head1 Version 0.49

Fixed how the C<< is => (ro|rw) >> works with custom defined
C<reader>, C<writer> and C<accessor> options. See the below table for
details:

  is => ro, writer => _foo    # turns into (reader => foo, writer => _foo)
  is => rw, writer => _foo    # turns into (reader => foo, writer => _foo)
  is => rw, accessor => _foo  # turns into (accessor => _foo)
  is => ro, accessor => _foo  # error, accesor is rw

=head1 Version 0.45

The C<before/around/after> method modifiers now support regexp
matching of method names. NOTE: this only works for classes, it is
currently not supported in roles, but, ... patches welcome.

The C<has> keyword for roles now accepts the same array ref form that
L<Moose>.pm does for classes.

A trigger on a read-only attribute is no longer an error, as it's
useful to trigger off of the constructor.

Subtypes of parameterizable types now are parameterizable types
themselves.

=head1 Version 0.44

Fixed issue where C<DEMOLISHALL> was eating the value in C<$@>, and so
not working correctly. It still kind of eats them, but so does vanilla
perl.

=head1 Version 0.41

Inherited attributes may now be extended without restriction on the
type ('isa', 'does').

The entire set of Moose::Meta::TypeConstraint::* classes were
refactored in this release. If you were relying on their internals you
should test your code carefully.

=head1 Version 0.40

Documenting the use of '+name' with attributes that come from recently
composed roles. It makes sense, people are using it, and so why not
just officially support it.

The C<< Moose::Meta::Class->create >> method now supports roles.

It is now possible to make anonymous enum types by passing C<enum> an
array reference instead of the C<< enum $name => @values >>.

=head1 Version 0.37

Added the C<make_immutable> keyword as a shortcut to calling
C<make_immutable> on the meta object. This eventually got removed!

Made C<< init_arg => undef >> work in Moose. This means "do not accept
a constructor parameter for this attribute".

Type errors now use the provided message. Prior to this release they
didn't.

=head1 Version 0.34

Moose is now a postmodern object system :)

The Role system was completely refactored. It is 100% backwards
compat, but the internals were totally changed. If you relied on the
internals then you are advised to test carefully.

Added method exclusion and aliasing for Roles in this release.

Added the L<Moose::Util::TypeConstraints::OptimizedConstraints>
module.

Passing a list of values to an accessor (which is only expecting one
value) used to be silently ignored, now it throws an error.

=head1 Version 0.26

Added parameterized types and did a pretty heavy refactoring of the
type constraint system.

Better framework extendability and better support for "making your own
Moose".

=head1 Version 0.25 or before

Honestly, you shouldn't be using versions of Moose that are this old,
so many bug fixes and speed improvements have been made you would be
crazy to not upgrade.

Also, I am tired of going through the Changelog so I am stopping here,
if anyone would like to continue this please feel free.

=head1 AUTHOR

Stevan Little E<lt>stevan@iinteractive.comE<gt>

=head1 COPYRIGHT AND LICENSE

Copyright 2009 by Infinity Interactive, Inc.

L<http://www.iinteractive.com>

This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.

=cut