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. If you have a
58 typed arrayref or hashref attribute where the type enforces a constraint on
59 the whole collection, this constraint will now be checked. It's possible that
60 code which previously ran without errors will now cause the constraint to
61 fail. However, presumably this is a good thing ;)
63 If you are passing invalid arguments to a delegation which were previously
64 being ignore, these will now fail.
66 The other issue is the use of a trigger. If your code relied on the trigger
67 only being called for a regular writer, that may cause problems.
69 As always, you are encouraged to test before deploying the latest version of
78 =item All deprecated features now warn
80 Previously, deprecation mostly consisted of simply saying "X is deprecated" in
81 the Changes file. We were not very consistent about actually warning. Now, all
82 deprecated features still present in Moose actually give a warning. The
83 warning is issued once per calling package. See L<Moose::Deprecated> for more
86 =item You cannot pass C<< coerce => 1 >> unless the attribute's type constraint has a coercion
88 Previously, this was accepted, and it sort of worked, except that if you
89 attempted to set the attribute after the object was created, you would get a
92 Now you will get a warning when you attempt to define the attribute.
94 =item C<no Moose>, C<no Moose::Role>, and C<no Moose::Exporter> no longer unimport strict and warnings
96 This change was made in 1.05, and has now been reverted. We don't know if the
97 user has explicitly loaded strict or warnings on their own, and unimporting
98 them is just broken in that case.
100 =item Reversed logic when defining which options can be changed
102 L<Moose::Meta::Attribute> now allows all options to be changed in an
103 overridden attribute. The previous behaviour required each option to be
104 whitelisted using the C<legal_options_for_inheritance> method. This method has
105 been removed, and there is a new method, C<illegal_options_for_inheritance>,
106 which can now be used to prevent certain options from being changeable.
108 In addition, we only throw an error if the illegal option is actually
109 changed. If the superclass didn't specify this option at all when defining the
110 attribute, the subclass version can still add it as an option.
112 Example of overriding this in an attribute trait:
114 package Bar::Meta::Attribute;
117 has 'my_illegal_option' => (
122 around illegal_options_for_inheritance => sub {
123 return ( shift->(@_), qw/my_illegal_option/ );
132 =item L<Moose::Object/BUILD> methods are now called when calling C<new_object>
134 Previously, C<BUILD> methods would only be called from C<Moose::Object::new>,
135 but now they are also called when constructing an object via
136 C<Moose::Meta::Class::new_object>. C<BUILD> methods are an inherent part of the
137 object construction process, and this should make C<< $meta->new_object >>
138 actually usable without forcing people to use C<< $meta->name->new >>.
140 =item C<no Moose>, C<no Moose::Role>, and C<no Moose::Exporter> now unimport strict and warnings
142 In the interest of having C<no Moose> clean up everything that C<use Moose>
143 does in the calling scope, C<no Moose> (as well as all other
144 L<Moose::Exporter>-using modules) now unimports strict and warnings.
146 =item Metaclass compatibility checking and fixing should be much more robust
148 The L<metaclass compatibility|Moose/METACLASS COMPATIBILITY AND MOOSE> checking
149 and fixing algorithms have been completely rewritten, in both Class::MOP and
150 Moose. This should resolve many confusing errors when dealing with non-Moose
151 inheritance and with custom metaclasses for things like attributes,
152 constructors, etc. For correct code, the only thing that should require a
153 change is that custom error metaclasses must now inherit from
154 L<Moose::Error::Default>.
162 =item Moose::Meta::TypeConstraint::Class is_subtype_of behavior
164 Earlier versions of L<is_subtype_of|Moose::Meta::TypeConstraint::Class/is_subtype_of>
165 would incorrectly return true when called with itself, its own TC name or
166 its class name as an argument. (i.e. $foo_tc->is_subtype_of('Foo') == 1) This
167 behavior was a caused by C<isa> being checked before the class name. The old
168 behavior can be accessed with L<is_type_of|Moose::Meta::TypeConstraint::Class/is_type_of>
176 =item Moose::Meta::Attribute::Native::Trait::Code no longer creates reader methods by default
178 Earlier versions of L<Moose::Meta::Attribute::Native::Trait::Code> created
179 read-only accessors for the attributes it's been applied to, even if you didn't
180 ask for it with C<< is => 'ro' >>. This incorrect behaviour has now been fixed.
188 =item Moose::Util add_method_modifier behavior
190 add_method_modifier (and subsequently the sugar functions Moose::before,
191 Moose::after, and Moose::around) can now accept arrayrefs, with the same
192 behavior as lists. Types other than arrayref and regexp result in an error.
196 =head1 0.93_01 and 0.94
200 =item Moose::Util::MetaRole API has changed
202 The C<apply_metaclass_roles> function is now called C<apply_metaroles>. The
203 way arguments are supplied has been changed to force you to distinguish
204 between metaroles applied to L<Moose::Meta::Class> (and helpers) versus
205 L<Moose::Meta::Role>.
207 The old API still works, but will warn in a future release, and eventually be
210 =item Moose::Meta::Role has real attributes
212 The attributes returned by L<Moose::Meta::Role> are now instances of the
213 L<Moose::Meta::Role::Attribute> class, instead of bare hash references.
215 =item "no Moose" now removes C<blessed> and C<confess>
217 Moose is now smart enough to know exactly what it exported, even when it
218 re-exports functions from other packages. When you unimport Moose, it will
219 remove these functions from your namespace unless you I<also> imported them
220 directly from their respective packages.
222 If you have a C<no Moose> in your code I<before> you call C<blessed> or
223 C<confess>, your code will break. You can either move the C<no Moose> call
224 later in your code, or explicitly import the relevant functions from the
225 packages that provide them.
227 =item L<Moose::Exporter> is smarter about unimporting re-exports
229 The change above comes from a general improvement to L<Moose::Exporter>. It
230 will now unimport any function it exports, even if that function is a
231 re-export from another package.
233 =item Attributes in roles can no longer override class attributes with "+foo"
235 Previously, this worked more or less accidentally, because role attributes
236 weren't objects. This was never documented, but a few MooseX modules took
239 =item The composition_class_roles attribute in L<Moose::Meta::Role> is now a method
241 This was done to make it possible for roles to alter the the list of
242 composition class roles by applying a method modifiers. Previously, this was
243 an attribute and MooseX modules override it. Since that no longer works, this
246 This I<should> be an attribute, so this may switch back to being an attribute
247 in the future if we can figure out how to make this work.
255 =item Calling $object->new() is no longer deprecated
257 We decided to undeprecate this. Now it just works.
259 =item Both C<get_method_map> and C<get_attribute_map> is deprecated
261 These metaclass methods were never meant to be public, and they are both now
262 deprecated. The work around if you still need the functionality they provided
263 is to iterate over the list of names manually.
265 my %fields = map { $_ => $meta->get_attribute($_) } $meta->get_attribute_list;
267 This was actually a change in L<Class::MOP>, but this version of Moose
268 requires a version of L<Class::MOP> that includes said change.
276 =item Added Native delegation for Code refs
278 See L<Moose::Meta::Attribute::Native::Trait::Code> for details.
280 =item Calling $object->new() is deprecated
282 Moose has long supported this, but it's never really been documented, and we
283 don't think this is a good practice. If you want to construct an object from
284 an existing object, you should provide some sort of alternate constructor like
285 C<< $object->clone >>.
287 Calling C<< $object->new >> now issues a warning, and will be an error in a
290 =item Moose no longer warns if you call C<make_immutable> for a class with mutable ancestors
292 While in theory this is a good thing to warn about, we found so many
293 exceptions to this that doing this properly became quite problematic.
301 =item New Native delegation methods from L<List::Util> and L<List::MoreUtils>
303 In particular, we now have C<reduce>, C<shuffle>, C<uniq>, and C<natatime>.
305 =item The Moose::Exporter with_caller feature is now deprecated
307 Use C<with_meta> instead. The C<with_caller> option will start warning in a
310 =item Moose now warns if you call C<make_immutable> for a class with mutable ancestors
312 This is dangerous because modifying a class after a subclass has been
313 immutabilized will lead to incorrect results in the subclass, due to inlining,
314 caching, etc. This occasionally happens accidentally, when a class loads one
315 of its subclasses in the middle of its class definition, so pointing out that
316 this may cause issues should be helpful. Metaclasses (classes that inherit
317 from L<Class::MOP::Object>) are currently exempt from this check, since at the
318 moment we aren't very consistent about which metaclasses we immutabilize.
320 =item C<enum> and C<duck_type> now take arrayrefs for all forms
322 Previously, calling these functions with a list would take the first element of
323 the list as the type constraint name, and use the remainder as the enum values
324 or method names. This makes the interface inconsistent with the anon-type forms
325 of these functions (which must take an arrayref), and a free-form list where
326 the first value is sometimes special is hard to validate (and harder to give
327 reasonable error messages for). These functions have been changed to take
328 arrayrefs in all their forms - so, C<< enum 'My::Type' => [qw(foo bar)] >> is
329 now the preferred way to create an enum type constraint. The old syntax still
330 works for now, but it will hopefully be deprecated and removed in a future
337 L<Moose::Meta::Attribute::Native> has been moved into the Moose core from
338 L<MooseX::AttributeHelpers>. Major changes include:
342 =item C<traits>, not C<metaclass>
344 Method providers are only available via traits.
346 =item C<handles>, not C<provides> or C<curries>
348 The C<provides> syntax was like core Moose C<< handles => HASHREF >>
349 syntax, but with the keys and values reversed. This was confusing,
350 and AttributeHelpers now uses C<< handles => HASHREF >> in a way that
351 should be intuitive to anyone already familiar with how it is used for
354 The C<curries> functionality provided by AttributeHelpers has been
355 generalized to apply to all cases of C<< handles => HASHREF >>, though
356 not every piece of functionality has been ported (currying with a
357 CODEREF is not supported).
359 =item C<empty> is now C<is_empty>, and means empty, not non-empty
361 Previously, the C<empty> method provided by Arrays and Hashes returned true if
362 the attribute was B<not> empty (no elements). Now it returns true if the
363 attribute B<is> empty. It was also renamed to C<is_empty>, to reflect this.
365 =item C<find> was renamed to C<first>, and C<first> and C<last> were removed
367 L<List::Util> refers to the functionality that we used to provide under C<find>
368 as L<first|List::Util/first>, so that will likely be more familiar (and will
369 fit in better if we decide to add more List::Util functions). C<first> and
370 C<last> were removed, since their functionality is easily duplicated with
373 =item Helpers that take a coderef of one argument now use C<$_>
375 Subroutines passed as the first argument to C<first>, C<map>, and C<grep> now
376 receive their argument in C<$_> rather than as a parameter to the subroutine.
377 Helpers that take a coderef of two or more arguments remain using the argument
378 list (there are technical limitations to using C<$a> and C<$b> like C<sort>
381 See L<Moose::Meta::Attribute::Native> for the new documentation.
385 The C<alias> and C<excludes> role parameters have been renamed to C<-alias>
386 and C<-excludes>. The old names still work, but new code should use the new
387 names, and eventually the old ones will be deprecated and removed.
391 C<< use Moose -metaclass => 'Foo' >> now does alias resolution, just like
392 C<-traits> (and the C<metaclass> and C<traits> options to C<has>).
394 Added two functions C<meta_class_alias> and C<meta_attribute_alias> to
395 L<Moose::Util>, to simplify aliasing metaclasses and metatraits. This is
396 a wrapper around the old
398 package Moose::Meta::Class::Custom::Trait::FooTrait;
399 sub register_implementation { 'My::Meta::Trait' }
405 When an attribute generates I<no> accessors, we now warn. This is to help
406 users who forget the C<is> option. If you really do not want any accessors,
407 you can use C<< is => 'bare' >>. You can maintain back compat with older
408 versions of Moose by using something like:
410 ($Moose::VERSION >= 0.84 ? is => 'bare' : ())
412 When an accessor overwrites an existing method, we now warn. To work around
413 this warning (if you really must have this behavior), you can explicitly
414 remove the method before creating it as an accessor:
418 __PACKAGE__->meta->remove_method('foo');
424 When an unknown option is passed to C<has>, we now warn. You can silence
425 the warning by fixing your code. :)
427 The C<Role> type has been deprecated. On its own, it was useless,
428 since it just checked C<< $object->can('does') >>. If you were using
429 it as a parent type, just call C<role_type('Role::Name')> to create an
430 appropriate type instead.
434 C<use Moose::Exporter;> now imports C<strict> and C<warnings> into packages
439 C<DEMOLISHALL> and C<DEMOLISH> now receive an argument indicating whether or
440 not we are in global destruction.
444 Type constraints no longer run coercions for a value that already matches the
445 constraint. This may affect some (arguably buggy) edge case coercions that
446 rely on side effects in the C<via> clause.
450 L<Moose::Exporter> now accepts the C<-metaclass> option for easily
451 overriding the metaclass (without L<metaclass>). This works for classes
456 Added a C<duck_type> sugar function to L<Moose::Util::TypeConstraints>
457 to make integration with non-Moose classes easier. It simply checks if
458 C<< $obj->can() >> a list of methods.
460 A number of methods (mostly inherited from L<Class::MOP>) have been
461 renamed with a leading underscore to indicate their internal-ness. The
462 old method names will still work for a while, but will warn that the
463 method has been renamed. In a few cases, the method will be removed
464 entirely in the future. This may affect MooseX authors who were using
469 Calling C<subtype> with a name as the only argument now throws an
470 exception. If you want an anonymous subtype do:
472 my $subtype = subtype as 'Foo';
474 This is related to the changes in version 0.71_01.
476 The C<is_needed> method in L<Moose::Meta::Method::Destructor> is now
477 only usable as a class method. Previously, it worked as a class or
478 object method, with a different internal implementation for each
481 The internals of making a class immutable changed a lot in Class::MOP
482 0.78_02, and Moose's internals have changed along with it. The
483 external C<< $metaclass->make_immutable >> method still works the same
488 A mutable class accepted C<< Foo->new(undef) >> without complaint,
489 while an immutable class would blow up with an unhelpful error. Now,
490 in both cases we throw a helpful error instead.
492 This "feature" was originally added to allow for cases such as this:
500 return My::Class->new($args);
502 But we decided this is a bad idea and a little too magical, because it
503 can easily mask real errors.
507 Calling C<type> or C<subtype> without the sugar helpers (C<as>,
508 C<where>, C<message>) is now deprecated.
510 As a side effect, this meant we ended up using Perl prototypes on
511 C<as>, and code like this will no longer work:
513 use Moose::Util::TypeConstraints;
514 use Declare::Constraints::Simple -All;
516 subtype 'ArrayOfInts'
518 => IsArrayRef(IsInt);
520 Instead it must be changed to this:
525 where => IsArrayRef(IsInt)
529 If you want to maintain backwards compat with older versions of Moose,
530 you must explicitly test Moose's C<VERSION>:
532 if ( Moose->VERSION < 0.71_01 ) {
533 subtype 'ArrayOfInts'
535 => IsArrayRef(IsInt);
541 where => IsArrayRef(IsInt)
548 We no longer pass the meta-attribute object as a final argument to
549 triggers. This actually changed for inlined code a while back, but the
550 non-inlined version and the docs were still out of date.
552 If by some chance you actually used this feature, the workaround is
553 simple. You fetch the attribute object from out of the C<$self>
554 that is passed as the first argument to trigger, like so:
560 my ( $self, $value ) = @_;
561 my $attr = $self->meta->find_attribute_by_name('foo');
569 If you created a subtype and passed a parent that Moose didn't know
570 about, it simply ignored the parent. Now it automatically creates the
571 parent as a class type. This may not be what you want, but is less
574 You could declare a name with subtype such as "Foo!Bar". Moose would
575 accept this allowed, but if you used it in a parameterized type such
576 as "ArrayRef[Foo!Bar]" it wouldn't work. We now do some vetting on
577 names created via the sugar functions, so that they can only contain
578 alphanumerics, ":", and ".".
582 Methods created via an attribute can now fulfill a C<requires>
583 declaration for a role. Honestly we don't know why Stevan didn't make
584 this work originally, he was just insane or something.
586 Stack traces from inlined code will now report the line and file as
587 being in your class, as opposed to in Moose guts.
591 When a class does not provide all of a role's required methods, the
592 error thrown now mentions all of the missing methods, as opposed to
593 just the first missing method.
595 Moose will no longer inline a constructor for your class unless it
596 inherits its constructor from Moose::Object, and will warn when it
597 doesn't inline. If you want to force inlining anyway, pass
598 C<< replace_constructor => 1 >> to C<make_immutable>.
600 If you want to get rid of the warning, pass C<< inline_constructor =>
605 Removed the (deprecated) C<make_immutable> keyword.
607 Removing an attribute from a class now also removes delegation
608 (C<handles>) methods installed for that attribute. This is correct
609 behavior, but if you were wrongly relying on it you might get bit.
613 Roles now add methods by calling C<add_method>, not
614 C<alias_method>. They make sure to always provide a method object,
615 which will be cloned internally. This means that it is now possible to
616 track the source of a method provided by a role, and even follow its
617 history through intermediate roles. This means that methods added by
618 a role now show up when looking at a class's method list/map.
620 Parameter and Union args are now sorted, this makes Int|Str the same
621 constraint as Str|Int. Also, incoming type constraint strings are
622 normalized to remove all whitespace differences. This is mostly for
623 internals and should not affect outside code.
625 L<Moose::Exporter> will no longer remove a subroutine that the
626 exporting package re-exports. Moose re-exports the Carp::confess
627 function, among others. The reasoning is that we cannot know whether
628 you have also explicitly imported those functions for your own use, so
629 we err on the safe side and always keep them.
633 C<Moose::init_meta> should now be called as a method.
635 New modules for extension writers, L<Moose::Exporter> and
636 L<Moose::Util::MetaRole>.
640 Implemented metaclass traits (and wrote a recipe for it):
642 use Moose -traits => 'Foo'
644 This should make writing small Moose extensions a little
649 Fixed C<coerce> to accept anon types just like C<subtype> can.
652 coerce $some_anon_type => from 'Str' => via { ... };
656 Added C<BUILDARGS>, a new step in C<< Moose::Object->new() >>.
660 Fixed how the C<< is => (ro|rw) >> works with custom defined
661 C<reader>, C<writer> and C<accessor> options. See the below table for
664 is => ro, writer => _foo # turns into (reader => foo, writer => _foo)
665 is => rw, writer => _foo # turns into (reader => foo, writer => _foo)
666 is => rw, accessor => _foo # turns into (accessor => _foo)
667 is => ro, accessor => _foo # error, accesor is rw
671 The C<before/around/after> method modifiers now support regexp
672 matching of method names. NOTE: this only works for classes, it is
673 currently not supported in roles, but, ... patches welcome.
675 The C<has> keyword for roles now accepts the same array ref form that
676 L<Moose>.pm does for classes.
678 A trigger on a read-only attribute is no longer an error, as it's
679 useful to trigger off of the constructor.
681 Subtypes of parameterizable types now are parameterizable types
686 Fixed issue where C<DEMOLISHALL> was eating the value in C<$@>, and so
687 not working correctly. It still kind of eats them, but so does vanilla
692 Inherited attributes may now be extended without restriction on the
693 type ('isa', 'does').
695 The entire set of Moose::Meta::TypeConstraint::* classes were
696 refactored in this release. If you were relying on their internals you
697 should test your code carefully.
701 Documenting the use of '+name' with attributes that come from recently
702 composed roles. It makes sense, people are using it, and so why not
703 just officially support it.
705 The C<< Moose::Meta::Class->create >> method now supports roles.
707 It is now possible to make anonymous enum types by passing C<enum> an
708 array reference instead of the C<< enum $name => @values >>.
712 Added the C<make_immutable> keyword as a shortcut to calling
713 C<make_immutable> on the meta object. This eventually got removed!
715 Made C<< init_arg => undef >> work in Moose. This means "do not accept
716 a constructor parameter for this attribute".
718 Type errors now use the provided message. Prior to this release they
723 Moose is now a postmodern object system :)
725 The Role system was completely refactored. It is 100% backwards
726 compat, but the internals were totally changed. If you relied on the
727 internals then you are advised to test carefully.
729 Added method exclusion and aliasing for Roles in this release.
731 Added the L<Moose::Util::TypeConstraints::OptimizedConstraints>
734 Passing a list of values to an accessor (which is only expecting one
735 value) used to be silently ignored, now it throws an error.
739 Added parameterized types and did a pretty heavy refactoring of the
740 type constraint system.
742 Better framework extendability and better support for "making your own
745 =head1 0.25 or before
747 Honestly, you shouldn't be using versions of Moose that are this old,
748 so many bug fixes and speed improvements have been made you would be
749 crazy to not upgrade.
751 Also, I am tired of going through the Changelog so I am stopping here,
752 if anyone would like to continue this please feel free.
756 Stevan Little E<lt>stevan@iinteractive.comE<gt>
758 =head1 COPYRIGHT AND LICENSE
760 Copyright 2009 by Infinity Interactive, Inc.
762 L<http://www.iinteractive.com>
764 This library is free software; you can redistribute it and/or modify
765 it under the same terms as Perl itself.