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 inlining 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 ignored, 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
77 =item Defaults is and default for String, Counter, and Bool
79 A few native traits (String, Counter, Bool) provide default values or "is" and
80 "default" when you created an attribute. Allowing them to provide these values
81 is now deprecated. Supply the value yourself when creating the attribute.
83 =item The C<meta> method
85 Moose and Class::MOP have been cleaned up internally enough to make the
86 C<meta> method that you get by default optional. C<use Moose> and
87 C<use Moose::Role> now can take an additional C<-meta_name> option, which
88 tells Moose what name to use when installing the C<meta> method. Passing
89 C<undef> to this option suppresses generation of the C<meta> method
90 entirely. This should be useful for users of modules which also use a C<meta>
91 method or function, such as L<Curses> or L<Rose::DB::Object>.
99 =item All deprecated features now warn
101 Previously, deprecation mostly consisted of simply saying "X is deprecated" in
102 the Changes file. We were not very consistent about actually warning. Now, all
103 deprecated features still present in Moose actually give a warning. The
104 warning is issued once per calling package. See L<Moose::Deprecated> for more
107 =item You cannot pass C<< coerce => 1 >> unless the attribute's type constraint has a coercion
109 Previously, this was accepted, and it sort of worked, except that if you
110 attempted to set the attribute after the object was created, you would get a
113 Now you will get a warning when you attempt to define the attribute.
115 =item C<no Moose>, C<no Moose::Role>, and C<no Moose::Exporter> no longer unimport strict and warnings
117 This change was made in 1.05, and has now been reverted. We don't know if the
118 user has explicitly loaded strict or warnings on their own, and unimporting
119 them is just broken in that case.
121 =item Reversed logic when defining which options can be changed
123 L<Moose::Meta::Attribute> now allows all options to be changed in an
124 overridden attribute. The previous behaviour required each option to be
125 whitelisted using the C<legal_options_for_inheritance> method. This method has
126 been removed, and there is a new method, C<illegal_options_for_inheritance>,
127 which can now be used to prevent certain options from being changeable.
129 In addition, we only throw an error if the illegal option is actually
130 changed. If the superclass didn't specify this option at all when defining the
131 attribute, the subclass version can still add it as an option.
133 Example of overriding this in an attribute trait:
135 package Bar::Meta::Attribute;
138 has 'my_illegal_option' => (
143 around illegal_options_for_inheritance => sub {
144 return ( shift->(@_), qw/my_illegal_option/ );
153 =item L<Moose::Object/BUILD> methods are now called when calling C<new_object>
155 Previously, C<BUILD> methods would only be called from C<Moose::Object::new>,
156 but now they are also called when constructing an object via
157 C<Moose::Meta::Class::new_object>. C<BUILD> methods are an inherent part of the
158 object construction process, and this should make C<< $meta->new_object >>
159 actually usable without forcing people to use C<< $meta->name->new >>.
161 =item C<no Moose>, C<no Moose::Role>, and C<no Moose::Exporter> now unimport strict and warnings
163 In the interest of having C<no Moose> clean up everything that C<use Moose>
164 does in the calling scope, C<no Moose> (as well as all other
165 L<Moose::Exporter>-using modules) now unimports strict and warnings.
167 =item Metaclass compatibility checking and fixing should be much more robust
169 The L<metaclass compatibility|Moose/METACLASS COMPATIBILITY AND MOOSE> checking
170 and fixing algorithms have been completely rewritten, in both Class::MOP and
171 Moose. This should resolve many confusing errors when dealing with non-Moose
172 inheritance and with custom metaclasses for things like attributes,
173 constructors, etc. For correct code, the only thing that should require a
174 change is that custom error metaclasses must now inherit from
175 L<Moose::Error::Default>.
183 =item Moose::Meta::TypeConstraint::Class is_subtype_of behavior
185 Earlier versions of L<is_subtype_of|Moose::Meta::TypeConstraint::Class/is_subtype_of>
186 would incorrectly return true when called with itself, its own TC name or
187 its class name as an argument. (i.e. $foo_tc->is_subtype_of('Foo') == 1) This
188 behavior was a caused by C<isa> being checked before the class name. The old
189 behavior can be accessed with L<is_type_of|Moose::Meta::TypeConstraint::Class/is_type_of>
197 =item Moose::Meta::Attribute::Native::Trait::Code no longer creates reader methods by default
199 Earlier versions of L<Moose::Meta::Attribute::Native::Trait::Code> created
200 read-only accessors for the attributes it's been applied to, even if you didn't
201 ask for it with C<< is => 'ro' >>. This incorrect behaviour has now been fixed.
209 =item Moose::Util add_method_modifier behavior
211 add_method_modifier (and subsequently the sugar functions Moose::before,
212 Moose::after, and Moose::around) can now accept arrayrefs, with the same
213 behavior as lists. Types other than arrayref and regexp result in an error.
217 =head1 0.93_01 and 0.94
221 =item Moose::Util::MetaRole API has changed
223 The C<apply_metaclass_roles> function is now called C<apply_metaroles>. The
224 way arguments are supplied has been changed to force you to distinguish
225 between metaroles applied to L<Moose::Meta::Class> (and helpers) versus
226 L<Moose::Meta::Role>.
228 The old API still works, but will warn in a future release, and eventually be
231 =item Moose::Meta::Role has real attributes
233 The attributes returned by L<Moose::Meta::Role> are now instances of the
234 L<Moose::Meta::Role::Attribute> class, instead of bare hash references.
236 =item "no Moose" now removes C<blessed> and C<confess>
238 Moose is now smart enough to know exactly what it exported, even when it
239 re-exports functions from other packages. When you unimport Moose, it will
240 remove these functions from your namespace unless you I<also> imported them
241 directly from their respective packages.
243 If you have a C<no Moose> in your code I<before> you call C<blessed> or
244 C<confess>, your code will break. You can either move the C<no Moose> call
245 later in your code, or explicitly import the relevant functions from the
246 packages that provide them.
248 =item L<Moose::Exporter> is smarter about unimporting re-exports
250 The change above comes from a general improvement to L<Moose::Exporter>. It
251 will now unimport any function it exports, even if that function is a
252 re-export from another package.
254 =item Attributes in roles can no longer override class attributes with "+foo"
256 Previously, this worked more or less accidentally, because role attributes
257 weren't objects. This was never documented, but a few MooseX modules took
260 =item The composition_class_roles attribute in L<Moose::Meta::Role> is now a method
262 This was done to make it possible for roles to alter the the list of
263 composition class roles by applying a method modifiers. Previously, this was
264 an attribute and MooseX modules override it. Since that no longer works, this
267 This I<should> be an attribute, so this may switch back to being an attribute
268 in the future if we can figure out how to make this work.
276 =item Calling $object->new() is no longer deprecated
278 We decided to undeprecate this. Now it just works.
280 =item Both C<get_method_map> and C<get_attribute_map> is deprecated
282 These metaclass methods were never meant to be public, and they are both now
283 deprecated. The work around if you still need the functionality they provided
284 is to iterate over the list of names manually.
286 my %fields = map { $_ => $meta->get_attribute($_) } $meta->get_attribute_list;
288 This was actually a change in L<Class::MOP>, but this version of Moose
289 requires a version of L<Class::MOP> that includes said change.
297 =item Added Native delegation for Code refs
299 See L<Moose::Meta::Attribute::Native::Trait::Code> for details.
301 =item Calling $object->new() is deprecated
303 Moose has long supported this, but it's never really been documented, and we
304 don't think this is a good practice. If you want to construct an object from
305 an existing object, you should provide some sort of alternate constructor like
306 C<< $object->clone >>.
308 Calling C<< $object->new >> now issues a warning, and will be an error in a
311 =item Moose no longer warns if you call C<make_immutable> for a class with mutable ancestors
313 While in theory this is a good thing to warn about, we found so many
314 exceptions to this that doing this properly became quite problematic.
322 =item New Native delegation methods from L<List::Util> and L<List::MoreUtils>
324 In particular, we now have C<reduce>, C<shuffle>, C<uniq>, and C<natatime>.
326 =item The Moose::Exporter with_caller feature is now deprecated
328 Use C<with_meta> instead. The C<with_caller> option will start warning in a
331 =item Moose now warns if you call C<make_immutable> for a class with mutable ancestors
333 This is dangerous because modifying a class after a subclass has been
334 immutabilized will lead to incorrect results in the subclass, due to inlining,
335 caching, etc. This occasionally happens accidentally, when a class loads one
336 of its subclasses in the middle of its class definition, so pointing out that
337 this may cause issues should be helpful. Metaclasses (classes that inherit
338 from L<Class::MOP::Object>) are currently exempt from this check, since at the
339 moment we aren't very consistent about which metaclasses we immutabilize.
341 =item C<enum> and C<duck_type> now take arrayrefs for all forms
343 Previously, calling these functions with a list would take the first element of
344 the list as the type constraint name, and use the remainder as the enum values
345 or method names. This makes the interface inconsistent with the anon-type forms
346 of these functions (which must take an arrayref), and a free-form list where
347 the first value is sometimes special is hard to validate (and harder to give
348 reasonable error messages for). These functions have been changed to take
349 arrayrefs in all their forms - so, C<< enum 'My::Type' => [qw(foo bar)] >> is
350 now the preferred way to create an enum type constraint. The old syntax still
351 works for now, but it will hopefully be deprecated and removed in a future
358 L<Moose::Meta::Attribute::Native> has been moved into the Moose core from
359 L<MooseX::AttributeHelpers>. Major changes include:
363 =item C<traits>, not C<metaclass>
365 Method providers are only available via traits.
367 =item C<handles>, not C<provides> or C<curries>
369 The C<provides> syntax was like core Moose C<< handles => HASHREF >>
370 syntax, but with the keys and values reversed. This was confusing,
371 and AttributeHelpers now uses C<< handles => HASHREF >> in a way that
372 should be intuitive to anyone already familiar with how it is used for
375 The C<curries> functionality provided by AttributeHelpers has been
376 generalized to apply to all cases of C<< handles => HASHREF >>, though
377 not every piece of functionality has been ported (currying with a
378 CODEREF is not supported).
380 =item C<empty> is now C<is_empty>, and means empty, not non-empty
382 Previously, the C<empty> method provided by Arrays and Hashes returned true if
383 the attribute was B<not> empty (no elements). Now it returns true if the
384 attribute B<is> empty. It was also renamed to C<is_empty>, to reflect this.
386 =item C<find> was renamed to C<first>, and C<first> and C<last> were removed
388 L<List::Util> refers to the functionality that we used to provide under C<find>
389 as L<first|List::Util/first>, so that will likely be more familiar (and will
390 fit in better if we decide to add more List::Util functions). C<first> and
391 C<last> were removed, since their functionality is easily duplicated with
394 =item Helpers that take a coderef of one argument now use C<$_>
396 Subroutines passed as the first argument to C<first>, C<map>, and C<grep> now
397 receive their argument in C<$_> rather than as a parameter to the subroutine.
398 Helpers that take a coderef of two or more arguments remain using the argument
399 list (there are technical limitations to using C<$a> and C<$b> like C<sort>
402 See L<Moose::Meta::Attribute::Native> for the new documentation.
406 The C<alias> and C<excludes> role parameters have been renamed to C<-alias>
407 and C<-excludes>. The old names still work, but new code should use the new
408 names, and eventually the old ones will be deprecated and removed.
412 C<< use Moose -metaclass => 'Foo' >> now does alias resolution, just like
413 C<-traits> (and the C<metaclass> and C<traits> options to C<has>).
415 Added two functions C<meta_class_alias> and C<meta_attribute_alias> to
416 L<Moose::Util>, to simplify aliasing metaclasses and metatraits. This is
417 a wrapper around the old
419 package Moose::Meta::Class::Custom::Trait::FooTrait;
420 sub register_implementation { 'My::Meta::Trait' }
426 When an attribute generates I<no> accessors, we now warn. This is to help
427 users who forget the C<is> option. If you really do not want any accessors,
428 you can use C<< is => 'bare' >>. You can maintain back compat with older
429 versions of Moose by using something like:
431 ($Moose::VERSION >= 0.84 ? is => 'bare' : ())
433 When an accessor overwrites an existing method, we now warn. To work around
434 this warning (if you really must have this behavior), you can explicitly
435 remove the method before creating it as an accessor:
439 __PACKAGE__->meta->remove_method('foo');
445 When an unknown option is passed to C<has>, we now warn. You can silence
446 the warning by fixing your code. :)
448 The C<Role> type has been deprecated. On its own, it was useless,
449 since it just checked C<< $object->can('does') >>. If you were using
450 it as a parent type, just call C<role_type('Role::Name')> to create an
451 appropriate type instead.
455 C<use Moose::Exporter;> now imports C<strict> and C<warnings> into packages
460 C<DEMOLISHALL> and C<DEMOLISH> now receive an argument indicating whether or
461 not we are in global destruction.
465 Type constraints no longer run coercions for a value that already matches the
466 constraint. This may affect some (arguably buggy) edge case coercions that
467 rely on side effects in the C<via> clause.
471 L<Moose::Exporter> now accepts the C<-metaclass> option for easily
472 overriding the metaclass (without L<metaclass>). This works for classes
477 Added a C<duck_type> sugar function to L<Moose::Util::TypeConstraints>
478 to make integration with non-Moose classes easier. It simply checks if
479 C<< $obj->can() >> a list of methods.
481 A number of methods (mostly inherited from L<Class::MOP>) have been
482 renamed with a leading underscore to indicate their internal-ness. The
483 old method names will still work for a while, but will warn that the
484 method has been renamed. In a few cases, the method will be removed
485 entirely in the future. This may affect MooseX authors who were using
490 Calling C<subtype> with a name as the only argument now throws an
491 exception. If you want an anonymous subtype do:
493 my $subtype = subtype as 'Foo';
495 This is related to the changes in version 0.71_01.
497 The C<is_needed> method in L<Moose::Meta::Method::Destructor> is now
498 only usable as a class method. Previously, it worked as a class or
499 object method, with a different internal implementation for each
502 The internals of making a class immutable changed a lot in Class::MOP
503 0.78_02, and Moose's internals have changed along with it. The
504 external C<< $metaclass->make_immutable >> method still works the same
509 A mutable class accepted C<< Foo->new(undef) >> without complaint,
510 while an immutable class would blow up with an unhelpful error. Now,
511 in both cases we throw a helpful error instead.
513 This "feature" was originally added to allow for cases such as this:
521 return My::Class->new($args);
523 But we decided this is a bad idea and a little too magical, because it
524 can easily mask real errors.
528 Calling C<type> or C<subtype> without the sugar helpers (C<as>,
529 C<where>, C<message>) is now deprecated.
531 As a side effect, this meant we ended up using Perl prototypes on
532 C<as>, and code like this will no longer work:
534 use Moose::Util::TypeConstraints;
535 use Declare::Constraints::Simple -All;
537 subtype 'ArrayOfInts'
539 => IsArrayRef(IsInt);
541 Instead it must be changed to this:
546 where => IsArrayRef(IsInt)
550 If you want to maintain backwards compat with older versions of Moose,
551 you must explicitly test Moose's C<VERSION>:
553 if ( Moose->VERSION < 0.71_01 ) {
554 subtype 'ArrayOfInts'
556 => IsArrayRef(IsInt);
562 where => IsArrayRef(IsInt)
569 We no longer pass the meta-attribute object as a final argument to
570 triggers. This actually changed for inlined code a while back, but the
571 non-inlined version and the docs were still out of date.
573 If by some chance you actually used this feature, the workaround is
574 simple. You fetch the attribute object from out of the C<$self>
575 that is passed as the first argument to trigger, like so:
581 my ( $self, $value ) = @_;
582 my $attr = $self->meta->find_attribute_by_name('foo');
590 If you created a subtype and passed a parent that Moose didn't know
591 about, it simply ignored the parent. Now it automatically creates the
592 parent as a class type. This may not be what you want, but is less
595 You could declare a name with subtype such as "Foo!Bar". Moose would
596 accept this allowed, but if you used it in a parameterized type such
597 as "ArrayRef[Foo!Bar]" it wouldn't work. We now do some vetting on
598 names created via the sugar functions, so that they can only contain
599 alphanumerics, ":", and ".".
603 Methods created via an attribute can now fulfill a C<requires>
604 declaration for a role. Honestly we don't know why Stevan didn't make
605 this work originally, he was just insane or something.
607 Stack traces from inlined code will now report the line and file as
608 being in your class, as opposed to in Moose guts.
612 When a class does not provide all of a role's required methods, the
613 error thrown now mentions all of the missing methods, as opposed to
614 just the first missing method.
616 Moose will no longer inline a constructor for your class unless it
617 inherits its constructor from Moose::Object, and will warn when it
618 doesn't inline. If you want to force inlining anyway, pass
619 C<< replace_constructor => 1 >> to C<make_immutable>.
621 If you want to get rid of the warning, pass C<< inline_constructor =>
626 Removed the (deprecated) C<make_immutable> keyword.
628 Removing an attribute from a class now also removes delegation
629 (C<handles>) methods installed for that attribute. This is correct
630 behavior, but if you were wrongly relying on it you might get bit.
634 Roles now add methods by calling C<add_method>, not
635 C<alias_method>. They make sure to always provide a method object,
636 which will be cloned internally. This means that it is now possible to
637 track the source of a method provided by a role, and even follow its
638 history through intermediate roles. This means that methods added by
639 a role now show up when looking at a class's method list/map.
641 Parameter and Union args are now sorted, this makes Int|Str the same
642 constraint as Str|Int. Also, incoming type constraint strings are
643 normalized to remove all whitespace differences. This is mostly for
644 internals and should not affect outside code.
646 L<Moose::Exporter> will no longer remove a subroutine that the
647 exporting package re-exports. Moose re-exports the Carp::confess
648 function, among others. The reasoning is that we cannot know whether
649 you have also explicitly imported those functions for your own use, so
650 we err on the safe side and always keep them.
654 C<Moose::init_meta> should now be called as a method.
656 New modules for extension writers, L<Moose::Exporter> and
657 L<Moose::Util::MetaRole>.
661 Implemented metaclass traits (and wrote a recipe for it):
663 use Moose -traits => 'Foo'
665 This should make writing small Moose extensions a little
670 Fixed C<coerce> to accept anon types just like C<subtype> can.
673 coerce $some_anon_type => from 'Str' => via { ... };
677 Added C<BUILDARGS>, a new step in C<< Moose::Object->new() >>.
681 Fixed how the C<< is => (ro|rw) >> works with custom defined
682 C<reader>, C<writer> and C<accessor> options. See the below table for
685 is => ro, writer => _foo # turns into (reader => foo, writer => _foo)
686 is => rw, writer => _foo # turns into (reader => foo, writer => _foo)
687 is => rw, accessor => _foo # turns into (accessor => _foo)
688 is => ro, accessor => _foo # error, accesor is rw
692 The C<before/around/after> method modifiers now support regexp
693 matching of method names. NOTE: this only works for classes, it is
694 currently not supported in roles, but, ... patches welcome.
696 The C<has> keyword for roles now accepts the same array ref form that
697 L<Moose>.pm does for classes.
699 A trigger on a read-only attribute is no longer an error, as it's
700 useful to trigger off of the constructor.
702 Subtypes of parameterizable types now are parameterizable types
707 Fixed issue where C<DEMOLISHALL> was eating the value in C<$@>, and so
708 not working correctly. It still kind of eats them, but so does vanilla
713 Inherited attributes may now be extended without restriction on the
714 type ('isa', 'does').
716 The entire set of Moose::Meta::TypeConstraint::* classes were
717 refactored in this release. If you were relying on their internals you
718 should test your code carefully.
722 Documenting the use of '+name' with attributes that come from recently
723 composed roles. It makes sense, people are using it, and so why not
724 just officially support it.
726 The C<< Moose::Meta::Class->create >> method now supports roles.
728 It is now possible to make anonymous enum types by passing C<enum> an
729 array reference instead of the C<< enum $name => @values >>.
733 Added the C<make_immutable> keyword as a shortcut to calling
734 C<make_immutable> on the meta object. This eventually got removed!
736 Made C<< init_arg => undef >> work in Moose. This means "do not accept
737 a constructor parameter for this attribute".
739 Type errors now use the provided message. Prior to this release they
744 Moose is now a postmodern object system :)
746 The Role system was completely refactored. It is 100% backwards
747 compat, but the internals were totally changed. If you relied on the
748 internals then you are advised to test carefully.
750 Added method exclusion and aliasing for Roles in this release.
752 Added the L<Moose::Util::TypeConstraints::OptimizedConstraints>
755 Passing a list of values to an accessor (which is only expecting one
756 value) used to be silently ignored, now it throws an error.
760 Added parameterized types and did a pretty heavy refactoring of the
761 type constraint system.
763 Better framework extendability and better support for "making your own
766 =head1 0.25 or before
768 Honestly, you shouldn't be using versions of Moose that are this old,
769 so many bug fixes and speed improvements have been made you would be
770 crazy to not upgrade.
772 Also, I am tired of going through the Changelog so I am stopping here,
773 if anyone would like to continue this please feel free.
777 Stevan Little E<lt>stevan@iinteractive.comE<gt>
779 =head1 COPYRIGHT AND LICENSE
781 Copyright 2009 by Infinity Interactive, Inc.
783 L<http://www.iinteractive.com>
785 This library is free software; you can redistribute it and/or modify
786 it under the same terms as Perl itself.