5 Moose::Manual::Delta - Important Changes in Moose
9 This documents any important or noteworthy changes in Moose, with a
10 focus on backwards. This does duplicate data from the F<Changes> file,
11 but aims to provide more details and when possible workarounds.
13 Besides helping keep up with changes, you can also use this document
14 for finding the lowest version of Moose that supported a given
15 feature. If you encounter a problem and have a solution but don't see
16 it documented here, or think we missed an important feature, please
25 In previous versions of Moose, the Native delegations were created as
26 closures. The generated code was often quite slow compared to doing the same
27 thing by hand. For example, the Array's push delegation ended up doing
30 push @{ $self->$reader() }, @_;
32 If the attribute was created without a reader, the C<$reader> sub reference
33 followed a very slow code path. Even with a reader, this is still slower than
36 Native delegations are now generated as inline code, just like other
37 accessors, so we can access the slot directly.
39 In addition, native traits now do proper constraint checking in all cases. In
40 particular, constraint checking has been improved for array and hash
41 references. Previously, only the I<contained> type (the C<Str> in
42 C<HashRef[Str]>) would be checked when a new value was added to the
43 collection. However, if there was a constraint that applied to the whole
44 value, this was never checked.
46 In addition, coercions are now called on the whole value.
48 The delegation methods now do more argument checking. All of the methods check
49 that a valid number of arguments were passed to the method. In addition, the
50 delegation methods check that the arguments are sane (array indexes, hash
51 keys, numbers, etc.) when applicable. We have tried to emulate the behavior of
52 Perl builtins as much as possible.
54 Finally, triggers are called whenever the value of the attribute is changed by
57 These changes are only likely to break code in a few cases.
59 The inlning code may or may not preserve the original reference when changes
60 are made. In some cases, methods which change the value may replace it
61 entirely. This will break tied values.
63 If you have a typed arrayref or hashref attribute where the type enforces a
64 constraint on the whole collection, this constraint will now be checked. It's
65 possible that code which previously ran without errors will now cause the
66 constraint to fail. However, presumably this is a good thing ;)
68 If you are passing invalid arguments to a delegation which were previously
69 being ignore, these calls will now fail.
71 If your code relied on the trigger only being called for a regular writer,
72 that may cause problems.
74 As always, you are encouraged to test before deploying the latest version of
83 =item All deprecated features now warn
85 Previously, deprecation mostly consisted of simply saying "X is deprecated" in
86 the Changes file. We were not very consistent about actually warning. Now, all
87 deprecated features still present in Moose actually give a warning. The
88 warning is issued once per calling package. See L<Moose::Deprecated> for more
91 =item You cannot pass C<< coerce => 1 >> unless the attribute's type constraint has a coercion
93 Previously, this was accepted, and it sort of worked, except that if you
94 attempted to set the attribute after the object was created, you would get a
97 Now you will get a warning when you attempt to define the attribute.
99 =item C<no Moose>, C<no Moose::Role>, and C<no Moose::Exporter> no longer unimport strict and warnings
101 This change was made in 1.05, and has now been reverted. We don't know if the
102 user has explicitly loaded strict or warnings on their own, and unimporting
103 them is just broken in that case.
105 =item Reversed logic when defining which options can be changed
107 L<Moose::Meta::Attribute> now allows all options to be changed in an
108 overridden attribute. The previous behaviour required each option to be
109 whitelisted using the C<legal_options_for_inheritance> method. This method has
110 been removed, and there is a new method, C<illegal_options_for_inheritance>,
111 which can now be used to prevent certain options from being changeable.
113 In addition, we only throw an error if the illegal option is actually
114 changed. If the superclass didn't specify this option at all when defining the
115 attribute, the subclass version can still add it as an option.
117 Example of overriding this in an attribute trait:
119 package Bar::Meta::Attribute;
122 has 'my_illegal_option' => (
127 around illegal_options_for_inheritance => sub {
128 return ( shift->(@_), qw/my_illegal_option/ );
137 =item L<Moose::Object/BUILD> methods are now called when calling C<new_object>
139 Previously, C<BUILD> methods would only be called from C<Moose::Object::new>,
140 but now they are also called when constructing an object via
141 C<Moose::Meta::Class::new_object>. C<BUILD> methods are an inherent part of the
142 object construction process, and this should make C<< $meta->new_object >>
143 actually usable without forcing people to use C<< $meta->name->new >>.
145 =item C<no Moose>, C<no Moose::Role>, and C<no Moose::Exporter> now unimport strict and warnings
147 In the interest of having C<no Moose> clean up everything that C<use Moose>
148 does in the calling scope, C<no Moose> (as well as all other
149 L<Moose::Exporter>-using modules) now unimports strict and warnings.
151 =item Metaclass compatibility checking and fixing should be much more robust
153 The L<metaclass compatibility|Moose/METACLASS COMPATIBILITY AND MOOSE> checking
154 and fixing algorithms have been completely rewritten, in both Class::MOP and
155 Moose. This should resolve many confusing errors when dealing with non-Moose
156 inheritance and with custom metaclasses for things like attributes,
157 constructors, etc. For correct code, the only thing that should require a
158 change is that custom error metaclasses must now inherit from
159 L<Moose::Error::Default>.
167 =item Moose::Meta::TypeConstraint::Class is_subtype_of behavior
169 Earlier versions of L<is_subtype_of|Moose::Meta::TypeConstraint::Class/is_subtype_of>
170 would incorrectly return true when called with itself, its own TC name or
171 its class name as an argument. (i.e. $foo_tc->is_subtype_of('Foo') == 1) This
172 behavior was a caused by C<isa> being checked before the class name. The old
173 behavior can be accessed with L<is_type_of|Moose::Meta::TypeConstraint::Class/is_type_of>
181 =item Moose::Meta::Attribute::Native::Trait::Code no longer creates reader methods by default
183 Earlier versions of L<Moose::Meta::Attribute::Native::Trait::Code> created
184 read-only accessors for the attributes it's been applied to, even if you didn't
185 ask for it with C<< is => 'ro' >>. This incorrect behaviour has now been fixed.
193 =item Moose::Util add_method_modifier behavior
195 add_method_modifier (and subsequently the sugar functions Moose::before,
196 Moose::after, and Moose::around) can now accept arrayrefs, with the same
197 behavior as lists. Types other than arrayref and regexp result in an error.
201 =head1 0.93_01 and 0.94
205 =item Moose::Util::MetaRole API has changed
207 The C<apply_metaclass_roles> function is now called C<apply_metaroles>. The
208 way arguments are supplied has been changed to force you to distinguish
209 between metaroles applied to L<Moose::Meta::Class> (and helpers) versus
210 L<Moose::Meta::Role>.
212 The old API still works, but will warn in a future release, and eventually be
215 =item Moose::Meta::Role has real attributes
217 The attributes returned by L<Moose::Meta::Role> are now instances of the
218 L<Moose::Meta::Role::Attribute> class, instead of bare hash references.
220 =item "no Moose" now removes C<blessed> and C<confess>
222 Moose is now smart enough to know exactly what it exported, even when it
223 re-exports functions from other packages. When you unimport Moose, it will
224 remove these functions from your namespace unless you I<also> imported them
225 directly from their respective packages.
227 If you have a C<no Moose> in your code I<before> you call C<blessed> or
228 C<confess>, your code will break. You can either move the C<no Moose> call
229 later in your code, or explicitly import the relevant functions from the
230 packages that provide them.
232 =item L<Moose::Exporter> is smarter about unimporting re-exports
234 The change above comes from a general improvement to L<Moose::Exporter>. It
235 will now unimport any function it exports, even if that function is a
236 re-export from another package.
238 =item Attributes in roles can no longer override class attributes with "+foo"
240 Previously, this worked more or less accidentally, because role attributes
241 weren't objects. This was never documented, but a few MooseX modules took
244 =item The composition_class_roles attribute in L<Moose::Meta::Role> is now a method
246 This was done to make it possible for roles to alter the the list of
247 composition class roles by applying a method modifiers. Previously, this was
248 an attribute and MooseX modules override it. Since that no longer works, this
251 This I<should> be an attribute, so this may switch back to being an attribute
252 in the future if we can figure out how to make this work.
260 =item Calling $object->new() is no longer deprecated
262 We decided to undeprecate this. Now it just works.
264 =item Both C<get_method_map> and C<get_attribute_map> is deprecated
266 These metaclass methods were never meant to be public, and they are both now
267 deprecated. The work around if you still need the functionality they provided
268 is to iterate over the list of names manually.
270 my %fields = map { $_ => $meta->get_attribute($_) } $meta->get_attribute_list;
272 This was actually a change in L<Class::MOP>, but this version of Moose
273 requires a version of L<Class::MOP> that includes said change.
281 =item Added Native delegation for Code refs
283 See L<Moose::Meta::Attribute::Native::Trait::Code> for details.
285 =item Calling $object->new() is deprecated
287 Moose has long supported this, but it's never really been documented, and we
288 don't think this is a good practice. If you want to construct an object from
289 an existing object, you should provide some sort of alternate constructor like
290 C<< $object->clone >>.
292 Calling C<< $object->new >> now issues a warning, and will be an error in a
295 =item Moose no longer warns if you call C<make_immutable> for a class with mutable ancestors
297 While in theory this is a good thing to warn about, we found so many
298 exceptions to this that doing this properly became quite problematic.
306 =item New Native delegation methods from L<List::Util> and L<List::MoreUtils>
308 In particular, we now have C<reduce>, C<shuffle>, C<uniq>, and C<natatime>.
310 =item The Moose::Exporter with_caller feature is now deprecated
312 Use C<with_meta> instead. The C<with_caller> option will start warning in a
315 =item Moose now warns if you call C<make_immutable> for a class with mutable ancestors
317 This is dangerous because modifying a class after a subclass has been
318 immutabilized will lead to incorrect results in the subclass, due to inlining,
319 caching, etc. This occasionally happens accidentally, when a class loads one
320 of its subclasses in the middle of its class definition, so pointing out that
321 this may cause issues should be helpful. Metaclasses (classes that inherit
322 from L<Class::MOP::Object>) are currently exempt from this check, since at the
323 moment we aren't very consistent about which metaclasses we immutabilize.
325 =item C<enum> and C<duck_type> now take arrayrefs for all forms
327 Previously, calling these functions with a list would take the first element of
328 the list as the type constraint name, and use the remainder as the enum values
329 or method names. This makes the interface inconsistent with the anon-type forms
330 of these functions (which must take an arrayref), and a free-form list where
331 the first value is sometimes special is hard to validate (and harder to give
332 reasonable error messages for). These functions have been changed to take
333 arrayrefs in all their forms - so, C<< enum 'My::Type' => [qw(foo bar)] >> is
334 now the preferred way to create an enum type constraint. The old syntax still
335 works for now, but it will hopefully be deprecated and removed in a future
342 L<Moose::Meta::Attribute::Native> has been moved into the Moose core from
343 L<MooseX::AttributeHelpers>. Major changes include:
347 =item C<traits>, not C<metaclass>
349 Method providers are only available via traits.
351 =item C<handles>, not C<provides> or C<curries>
353 The C<provides> syntax was like core Moose C<< handles => HASHREF >>
354 syntax, but with the keys and values reversed. This was confusing,
355 and AttributeHelpers now uses C<< handles => HASHREF >> in a way that
356 should be intuitive to anyone already familiar with how it is used for
359 The C<curries> functionality provided by AttributeHelpers has been
360 generalized to apply to all cases of C<< handles => HASHREF >>, though
361 not every piece of functionality has been ported (currying with a
362 CODEREF is not supported).
364 =item C<empty> is now C<is_empty>, and means empty, not non-empty
366 Previously, the C<empty> method provided by Arrays and Hashes returned true if
367 the attribute was B<not> empty (no elements). Now it returns true if the
368 attribute B<is> empty. It was also renamed to C<is_empty>, to reflect this.
370 =item C<find> was renamed to C<first>, and C<first> and C<last> were removed
372 L<List::Util> refers to the functionality that we used to provide under C<find>
373 as L<first|List::Util/first>, so that will likely be more familiar (and will
374 fit in better if we decide to add more List::Util functions). C<first> and
375 C<last> were removed, since their functionality is easily duplicated with
378 =item Helpers that take a coderef of one argument now use C<$_>
380 Subroutines passed as the first argument to C<first>, C<map>, and C<grep> now
381 receive their argument in C<$_> rather than as a parameter to the subroutine.
382 Helpers that take a coderef of two or more arguments remain using the argument
383 list (there are technical limitations to using C<$a> and C<$b> like C<sort>
386 See L<Moose::Meta::Attribute::Native> for the new documentation.
390 The C<alias> and C<excludes> role parameters have been renamed to C<-alias>
391 and C<-excludes>. The old names still work, but new code should use the new
392 names, and eventually the old ones will be deprecated and removed.
396 C<< use Moose -metaclass => 'Foo' >> now does alias resolution, just like
397 C<-traits> (and the C<metaclass> and C<traits> options to C<has>).
399 Added two functions C<meta_class_alias> and C<meta_attribute_alias> to
400 L<Moose::Util>, to simplify aliasing metaclasses and metatraits. This is
401 a wrapper around the old
403 package Moose::Meta::Class::Custom::Trait::FooTrait;
404 sub register_implementation { 'My::Meta::Trait' }
410 When an attribute generates I<no> accessors, we now warn. This is to help
411 users who forget the C<is> option. If you really do not want any accessors,
412 you can use C<< is => 'bare' >>. You can maintain back compat with older
413 versions of Moose by using something like:
415 ($Moose::VERSION >= 0.84 ? is => 'bare' : ())
417 When an accessor overwrites an existing method, we now warn. To work around
418 this warning (if you really must have this behavior), you can explicitly
419 remove the method before creating it as an accessor:
423 __PACKAGE__->meta->remove_method('foo');
429 When an unknown option is passed to C<has>, we now warn. You can silence
430 the warning by fixing your code. :)
432 The C<Role> type has been deprecated. On its own, it was useless,
433 since it just checked C<< $object->can('does') >>. If you were using
434 it as a parent type, just call C<role_type('Role::Name')> to create an
435 appropriate type instead.
439 C<use Moose::Exporter;> now imports C<strict> and C<warnings> into packages
444 C<DEMOLISHALL> and C<DEMOLISH> now receive an argument indicating whether or
445 not we are in global destruction.
449 Type constraints no longer run coercions for a value that already matches the
450 constraint. This may affect some (arguably buggy) edge case coercions that
451 rely on side effects in the C<via> clause.
455 L<Moose::Exporter> now accepts the C<-metaclass> option for easily
456 overriding the metaclass (without L<metaclass>). This works for classes
461 Added a C<duck_type> sugar function to L<Moose::Util::TypeConstraints>
462 to make integration with non-Moose classes easier. It simply checks if
463 C<< $obj->can() >> a list of methods.
465 A number of methods (mostly inherited from L<Class::MOP>) have been
466 renamed with a leading underscore to indicate their internal-ness. The
467 old method names will still work for a while, but will warn that the
468 method has been renamed. In a few cases, the method will be removed
469 entirely in the future. This may affect MooseX authors who were using
474 Calling C<subtype> with a name as the only argument now throws an
475 exception. If you want an anonymous subtype do:
477 my $subtype = subtype as 'Foo';
479 This is related to the changes in version 0.71_01.
481 The C<is_needed> method in L<Moose::Meta::Method::Destructor> is now
482 only usable as a class method. Previously, it worked as a class or
483 object method, with a different internal implementation for each
486 The internals of making a class immutable changed a lot in Class::MOP
487 0.78_02, and Moose's internals have changed along with it. The
488 external C<< $metaclass->make_immutable >> method still works the same
493 A mutable class accepted C<< Foo->new(undef) >> without complaint,
494 while an immutable class would blow up with an unhelpful error. Now,
495 in both cases we throw a helpful error instead.
497 This "feature" was originally added to allow for cases such as this:
505 return My::Class->new($args);
507 But we decided this is a bad idea and a little too magical, because it
508 can easily mask real errors.
512 Calling C<type> or C<subtype> without the sugar helpers (C<as>,
513 C<where>, C<message>) is now deprecated.
515 As a side effect, this meant we ended up using Perl prototypes on
516 C<as>, and code like this will no longer work:
518 use Moose::Util::TypeConstraints;
519 use Declare::Constraints::Simple -All;
521 subtype 'ArrayOfInts'
523 => IsArrayRef(IsInt);
525 Instead it must be changed to this:
530 where => IsArrayRef(IsInt)
534 If you want to maintain backwards compat with older versions of Moose,
535 you must explicitly test Moose's C<VERSION>:
537 if ( Moose->VERSION < 0.71_01 ) {
538 subtype 'ArrayOfInts'
540 => IsArrayRef(IsInt);
546 where => IsArrayRef(IsInt)
553 We no longer pass the meta-attribute object as a final argument to
554 triggers. This actually changed for inlined code a while back, but the
555 non-inlined version and the docs were still out of date.
557 If by some chance you actually used this feature, the workaround is
558 simple. You fetch the attribute object from out of the C<$self>
559 that is passed as the first argument to trigger, like so:
565 my ( $self, $value ) = @_;
566 my $attr = $self->meta->find_attribute_by_name('foo');
574 If you created a subtype and passed a parent that Moose didn't know
575 about, it simply ignored the parent. Now it automatically creates the
576 parent as a class type. This may not be what you want, but is less
579 You could declare a name with subtype such as "Foo!Bar". Moose would
580 accept this allowed, but if you used it in a parameterized type such
581 as "ArrayRef[Foo!Bar]" it wouldn't work. We now do some vetting on
582 names created via the sugar functions, so that they can only contain
583 alphanumerics, ":", and ".".
587 Methods created via an attribute can now fulfill a C<requires>
588 declaration for a role. Honestly we don't know why Stevan didn't make
589 this work originally, he was just insane or something.
591 Stack traces from inlined code will now report the line and file as
592 being in your class, as opposed to in Moose guts.
596 When a class does not provide all of a role's required methods, the
597 error thrown now mentions all of the missing methods, as opposed to
598 just the first missing method.
600 Moose will no longer inline a constructor for your class unless it
601 inherits its constructor from Moose::Object, and will warn when it
602 doesn't inline. If you want to force inlining anyway, pass
603 C<< replace_constructor => 1 >> to C<make_immutable>.
605 If you want to get rid of the warning, pass C<< inline_constructor =>
610 Removed the (deprecated) C<make_immutable> keyword.
612 Removing an attribute from a class now also removes delegation
613 (C<handles>) methods installed for that attribute. This is correct
614 behavior, but if you were wrongly relying on it you might get bit.
618 Roles now add methods by calling C<add_method>, not
619 C<alias_method>. They make sure to always provide a method object,
620 which will be cloned internally. This means that it is now possible to
621 track the source of a method provided by a role, and even follow its
622 history through intermediate roles. This means that methods added by
623 a role now show up when looking at a class's method list/map.
625 Parameter and Union args are now sorted, this makes Int|Str the same
626 constraint as Str|Int. Also, incoming type constraint strings are
627 normalized to remove all whitespace differences. This is mostly for
628 internals and should not affect outside code.
630 L<Moose::Exporter> will no longer remove a subroutine that the
631 exporting package re-exports. Moose re-exports the Carp::confess
632 function, among others. The reasoning is that we cannot know whether
633 you have also explicitly imported those functions for your own use, so
634 we err on the safe side and always keep them.
638 C<Moose::init_meta> should now be called as a method.
640 New modules for extension writers, L<Moose::Exporter> and
641 L<Moose::Util::MetaRole>.
645 Implemented metaclass traits (and wrote a recipe for it):
647 use Moose -traits => 'Foo'
649 This should make writing small Moose extensions a little
654 Fixed C<coerce> to accept anon types just like C<subtype> can.
657 coerce $some_anon_type => from 'Str' => via { ... };
661 Added C<BUILDARGS>, a new step in C<< Moose::Object->new() >>.
665 Fixed how the C<< is => (ro|rw) >> works with custom defined
666 C<reader>, C<writer> and C<accessor> options. See the below table for
669 is => ro, writer => _foo # turns into (reader => foo, writer => _foo)
670 is => rw, writer => _foo # turns into (reader => foo, writer => _foo)
671 is => rw, accessor => _foo # turns into (accessor => _foo)
672 is => ro, accessor => _foo # error, accesor is rw
676 The C<before/around/after> method modifiers now support regexp
677 matching of method names. NOTE: this only works for classes, it is
678 currently not supported in roles, but, ... patches welcome.
680 The C<has> keyword for roles now accepts the same array ref form that
681 L<Moose>.pm does for classes.
683 A trigger on a read-only attribute is no longer an error, as it's
684 useful to trigger off of the constructor.
686 Subtypes of parameterizable types now are parameterizable types
691 Fixed issue where C<DEMOLISHALL> was eating the value in C<$@>, and so
692 not working correctly. It still kind of eats them, but so does vanilla
697 Inherited attributes may now be extended without restriction on the
698 type ('isa', 'does').
700 The entire set of Moose::Meta::TypeConstraint::* classes were
701 refactored in this release. If you were relying on their internals you
702 should test your code carefully.
706 Documenting the use of '+name' with attributes that come from recently
707 composed roles. It makes sense, people are using it, and so why not
708 just officially support it.
710 The C<< Moose::Meta::Class->create >> method now supports roles.
712 It is now possible to make anonymous enum types by passing C<enum> an
713 array reference instead of the C<< enum $name => @values >>.
717 Added the C<make_immutable> keyword as a shortcut to calling
718 C<make_immutable> on the meta object. This eventually got removed!
720 Made C<< init_arg => undef >> work in Moose. This means "do not accept
721 a constructor parameter for this attribute".
723 Type errors now use the provided message. Prior to this release they
728 Moose is now a postmodern object system :)
730 The Role system was completely refactored. It is 100% backwards
731 compat, but the internals were totally changed. If you relied on the
732 internals then you are advised to test carefully.
734 Added method exclusion and aliasing for Roles in this release.
736 Added the L<Moose::Util::TypeConstraints::OptimizedConstraints>
739 Passing a list of values to an accessor (which is only expecting one
740 value) used to be silently ignored, now it throws an error.
744 Added parameterized types and did a pretty heavy refactoring of the
745 type constraint system.
747 Better framework extendability and better support for "making your own
750 =head1 0.25 or before
752 Honestly, you shouldn't be using versions of Moose that are this old,
753 so many bug fixes and speed improvements have been made you would be
754 crazy to not upgrade.
756 Also, I am tired of going through the Changelog so I am stopping here,
757 if anyone would like to continue this please feel free.
761 Stevan Little E<lt>stevan@iinteractive.comE<gt>
763 =head1 COPYRIGHT AND LICENSE
765 Copyright 2009 by Infinity Interactive, Inc.
767 L<http://www.iinteractive.com>
769 This library is free software; you can redistribute it and/or modify
770 it under the same terms as Perl itself.