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
23 =item Configurable stacktraces
25 Classes which use the L<Moose::Error::Default> error class can now have
26 stacktraces disabled by setting the C<MOOSE_ERROR_STYLE> env var to C<croak>.
27 This is experimental, fairly incomplete, and won't work in all cases (because
28 Moose's error system in general is all of these things), but this should allow
29 for reducing at least some of the verbosity in most cases.
37 =item Native Delegations
39 In previous versions of Moose, the Native delegations were created as
40 closures. The generated code was often quite slow compared to doing the same
41 thing by hand. For example, the Array's push delegation ended up doing
44 push @{ $self->$reader() }, @_;
46 If the attribute was created without a reader, the C<$reader> sub reference
47 followed a very slow code path. Even with a reader, this is still slower than
50 Native delegations are now generated as inline code, just like other
51 accessors, so we can access the slot directly.
53 In addition, native traits now do proper constraint checking in all cases. In
54 particular, constraint checking has been improved for array and hash
55 references. Previously, only the I<contained> type (the C<Str> in
56 C<HashRef[Str]>) would be checked when a new value was added to the
57 collection. However, if there was a constraint that applied to the whole
58 value, this was never checked.
60 In addition, coercions are now called on the whole value.
62 The delegation methods now do more argument checking. All of the methods check
63 that a valid number of arguments were passed to the method. In addition, the
64 delegation methods check that the arguments are sane (array indexes, hash
65 keys, numbers, etc.) when applicable. We have tried to emulate the behavior of
66 Perl builtins as much as possible.
68 Finally, triggers are called whenever the value of the attribute is changed by
71 These changes are only likely to break code in a few cases.
73 The inlining code may or may not preserve the original reference when changes
74 are made. In some cases, methods which change the value may replace it
75 entirely. This will break tied values.
77 If you have a typed arrayref or hashref attribute where the type enforces a
78 constraint on the whole collection, this constraint will now be checked. It's
79 possible that code which previously ran without errors will now cause the
80 constraint to fail. However, presumably this is a good thing ;)
82 If you are passing invalid arguments to a delegation which were previously
83 being ignored, these calls will now fail.
85 If your code relied on the trigger only being called for a regular writer,
86 that may cause problems.
88 As always, you are encouraged to test before deploying the latest version of
91 =item Defaults is and default for String, Counter, and Bool
93 A few native traits (String, Counter, Bool) provide default values of "is" and
94 "default" when you created an attribute. Allowing them to provide these values
95 is now deprecated. Supply the value yourself when creating the attribute.
97 =item The C<meta> method
99 Moose and Class::MOP have been cleaned up internally enough to make the
100 C<meta> method that you get by default optional. C<use Moose> and
101 C<use Moose::Role> now can take an additional C<-meta_name> option, which
102 tells Moose what name to use when installing the C<meta> method. Passing
103 C<undef> to this option suppresses generation of the C<meta> method
104 entirely. This should be useful for users of modules which also use a C<meta>
105 method or function, such as L<Curses> or L<Rose::DB::Object>.
113 =item All deprecated features now warn
115 Previously, deprecation mostly consisted of simply saying "X is deprecated" in
116 the Changes file. We were not very consistent about actually warning. Now, all
117 deprecated features still present in Moose actually give a warning. The
118 warning is issued once per calling package. See L<Moose::Deprecated> for more
121 =item You cannot pass C<< coerce => 1 >> unless the attribute's type constraint has a coercion
123 Previously, this was accepted, and it sort of worked, except that if you
124 attempted to set the attribute after the object was created, you would get a
127 Now you will get a warning when you attempt to define the attribute.
129 =item C<no Moose>, C<no Moose::Role>, and C<no Moose::Exporter> no longer unimport strict and warnings
131 This change was made in 1.05, and has now been reverted. We don't know if the
132 user has explicitly loaded strict or warnings on their own, and unimporting
133 them is just broken in that case.
135 =item Reversed logic when defining which options can be changed
137 L<Moose::Meta::Attribute> now allows all options to be changed in an
138 overridden attribute. The previous behaviour required each option to be
139 whitelisted using the C<legal_options_for_inheritance> method. This method has
140 been removed, and there is a new method, C<illegal_options_for_inheritance>,
141 which can now be used to prevent certain options from being changeable.
143 In addition, we only throw an error if the illegal option is actually
144 changed. If the superclass didn't specify this option at all when defining the
145 attribute, the subclass version can still add it as an option.
147 Example of overriding this in an attribute trait:
149 package Bar::Meta::Attribute;
152 has 'my_illegal_option' => (
157 around illegal_options_for_inheritance => sub {
158 return ( shift->(@_), qw/my_illegal_option/ );
167 =item L<Moose::Object/BUILD> methods are now called when calling C<new_object>
169 Previously, C<BUILD> methods would only be called from C<Moose::Object::new>,
170 but now they are also called when constructing an object via
171 C<Moose::Meta::Class::new_object>. C<BUILD> methods are an inherent part of the
172 object construction process, and this should make C<< $meta->new_object >>
173 actually usable without forcing people to use C<< $meta->name->new >>.
175 =item C<no Moose>, C<no Moose::Role>, and C<no Moose::Exporter> now unimport strict and warnings
177 In the interest of having C<no Moose> clean up everything that C<use Moose>
178 does in the calling scope, C<no Moose> (as well as all other
179 L<Moose::Exporter>-using modules) now unimports strict and warnings.
181 =item Metaclass compatibility checking and fixing should be much more robust
183 The L<metaclass compatibility|Moose/METACLASS COMPATIBILITY AND MOOSE> checking
184 and fixing algorithms have been completely rewritten, in both Class::MOP and
185 Moose. This should resolve many confusing errors when dealing with non-Moose
186 inheritance and with custom metaclasses for things like attributes,
187 constructors, etc. For correct code, the only thing that should require a
188 change is that custom error metaclasses must now inherit from
189 L<Moose::Error::Default>.
197 =item Moose::Meta::TypeConstraint::Class is_subtype_of behavior
199 Earlier versions of L<is_subtype_of|Moose::Meta::TypeConstraint::Class/is_subtype_of>
200 would incorrectly return true when called with itself, its own TC name or
201 its class name as an argument. (i.e. $foo_tc->is_subtype_of('Foo') == 1) This
202 behavior was a caused by C<isa> being checked before the class name. The old
203 behavior can be accessed with L<is_type_of|Moose::Meta::TypeConstraint::Class/is_type_of>
211 =item Moose::Meta::Attribute::Native::Trait::Code no longer creates reader methods by default
213 Earlier versions of L<Moose::Meta::Attribute::Native::Trait::Code> created
214 read-only accessors for the attributes it's been applied to, even if you didn't
215 ask for it with C<< is => 'ro' >>. This incorrect behaviour has now been fixed.
223 =item Moose::Util add_method_modifier behavior
225 add_method_modifier (and subsequently the sugar functions Moose::before,
226 Moose::after, and Moose::around) can now accept arrayrefs, with the same
227 behavior as lists. Types other than arrayref and regexp result in an error.
231 =head1 0.93_01 and 0.94
235 =item Moose::Util::MetaRole API has changed
237 The C<apply_metaclass_roles> function is now called C<apply_metaroles>. The
238 way arguments are supplied has been changed to force you to distinguish
239 between metaroles applied to L<Moose::Meta::Class> (and helpers) versus
240 L<Moose::Meta::Role>.
242 The old API still works, but will warn in a future release, and eventually be
245 =item Moose::Meta::Role has real attributes
247 The attributes returned by L<Moose::Meta::Role> are now instances of the
248 L<Moose::Meta::Role::Attribute> class, instead of bare hash references.
250 =item "no Moose" now removes C<blessed> and C<confess>
252 Moose is now smart enough to know exactly what it exported, even when it
253 re-exports functions from other packages. When you unimport Moose, it will
254 remove these functions from your namespace unless you I<also> imported them
255 directly from their respective packages.
257 If you have a C<no Moose> in your code I<before> you call C<blessed> or
258 C<confess>, your code will break. You can either move the C<no Moose> call
259 later in your code, or explicitly import the relevant functions from the
260 packages that provide them.
262 =item L<Moose::Exporter> is smarter about unimporting re-exports
264 The change above comes from a general improvement to L<Moose::Exporter>. It
265 will now unimport any function it exports, even if that function is a
266 re-export from another package.
268 =item Attributes in roles can no longer override class attributes with "+foo"
270 Previously, this worked more or less accidentally, because role attributes
271 weren't objects. This was never documented, but a few MooseX modules took
274 =item The composition_class_roles attribute in L<Moose::Meta::Role> is now a method
276 This was done to make it possible for roles to alter the the list of
277 composition class roles by applying a method modifiers. Previously, this was
278 an attribute and MooseX modules override it. Since that no longer works, this
281 This I<should> be an attribute, so this may switch back to being an attribute
282 in the future if we can figure out how to make this work.
290 =item Calling $object->new() is no longer deprecated
292 We decided to undeprecate this. Now it just works.
294 =item Both C<get_method_map> and C<get_attribute_map> is deprecated
296 These metaclass methods were never meant to be public, and they are both now
297 deprecated. The work around if you still need the functionality they provided
298 is to iterate over the list of names manually.
300 my %fields = map { $_ => $meta->get_attribute($_) } $meta->get_attribute_list;
302 This was actually a change in L<Class::MOP>, but this version of Moose
303 requires a version of L<Class::MOP> that includes said change.
311 =item Added Native delegation for Code refs
313 See L<Moose::Meta::Attribute::Native::Trait::Code> for details.
315 =item Calling $object->new() is deprecated
317 Moose has long supported this, but it's never really been documented, and we
318 don't think this is a good practice. If you want to construct an object from
319 an existing object, you should provide some sort of alternate constructor like
320 C<< $object->clone >>.
322 Calling C<< $object->new >> now issues a warning, and will be an error in a
325 =item Moose no longer warns if you call C<make_immutable> for a class with mutable ancestors
327 While in theory this is a good thing to warn about, we found so many
328 exceptions to this that doing this properly became quite problematic.
336 =item New Native delegation methods from L<List::Util> and L<List::MoreUtils>
338 In particular, we now have C<reduce>, C<shuffle>, C<uniq>, and C<natatime>.
340 =item The Moose::Exporter with_caller feature is now deprecated
342 Use C<with_meta> instead. The C<with_caller> option will start warning in a
345 =item Moose now warns if you call C<make_immutable> for a class with mutable ancestors
347 This is dangerous because modifying a class after a subclass has been
348 immutabilized will lead to incorrect results in the subclass, due to inlining,
349 caching, etc. This occasionally happens accidentally, when a class loads one
350 of its subclasses in the middle of its class definition, so pointing out that
351 this may cause issues should be helpful. Metaclasses (classes that inherit
352 from L<Class::MOP::Object>) are currently exempt from this check, since at the
353 moment we aren't very consistent about which metaclasses we immutabilize.
355 =item C<enum> and C<duck_type> now take arrayrefs for all forms
357 Previously, calling these functions with a list would take the first element of
358 the list as the type constraint name, and use the remainder as the enum values
359 or method names. This makes the interface inconsistent with the anon-type forms
360 of these functions (which must take an arrayref), and a free-form list where
361 the first value is sometimes special is hard to validate (and harder to give
362 reasonable error messages for). These functions have been changed to take
363 arrayrefs in all their forms - so, C<< enum 'My::Type' => [qw(foo bar)] >> is
364 now the preferred way to create an enum type constraint. The old syntax still
365 works for now, but it will hopefully be deprecated and removed in a future
372 L<Moose::Meta::Attribute::Native> has been moved into the Moose core from
373 L<MooseX::AttributeHelpers>. Major changes include:
377 =item C<traits>, not C<metaclass>
379 Method providers are only available via traits.
381 =item C<handles>, not C<provides> or C<curries>
383 The C<provides> syntax was like core Moose C<< handles => HASHREF >>
384 syntax, but with the keys and values reversed. This was confusing,
385 and AttributeHelpers now uses C<< handles => HASHREF >> in a way that
386 should be intuitive to anyone already familiar with how it is used for
389 The C<curries> functionality provided by AttributeHelpers has been
390 generalized to apply to all cases of C<< handles => HASHREF >>, though
391 not every piece of functionality has been ported (currying with a
392 CODEREF is not supported).
394 =item C<empty> is now C<is_empty>, and means empty, not non-empty
396 Previously, the C<empty> method provided by Arrays and Hashes returned true if
397 the attribute was B<not> empty (no elements). Now it returns true if the
398 attribute B<is> empty. It was also renamed to C<is_empty>, to reflect this.
400 =item C<find> was renamed to C<first>, and C<first> and C<last> were removed
402 L<List::Util> refers to the functionality that we used to provide under C<find>
403 as L<first|List::Util/first>, so that will likely be more familiar (and will
404 fit in better if we decide to add more List::Util functions). C<first> and
405 C<last> were removed, since their functionality is easily duplicated with
408 =item Helpers that take a coderef of one argument now use C<$_>
410 Subroutines passed as the first argument to C<first>, C<map>, and C<grep> now
411 receive their argument in C<$_> rather than as a parameter to the subroutine.
412 Helpers that take a coderef of two or more arguments remain using the argument
413 list (there are technical limitations to using C<$a> and C<$b> like C<sort>
416 See L<Moose::Meta::Attribute::Native> for the new documentation.
420 The C<alias> and C<excludes> role parameters have been renamed to C<-alias>
421 and C<-excludes>. The old names still work, but new code should use the new
422 names, and eventually the old ones will be deprecated and removed.
426 C<< use Moose -metaclass => 'Foo' >> now does alias resolution, just like
427 C<-traits> (and the C<metaclass> and C<traits> options to C<has>).
429 Added two functions C<meta_class_alias> and C<meta_attribute_alias> to
430 L<Moose::Util>, to simplify aliasing metaclasses and metatraits. This is
431 a wrapper around the old
433 package Moose::Meta::Class::Custom::Trait::FooTrait;
434 sub register_implementation { 'My::Meta::Trait' }
440 When an attribute generates I<no> accessors, we now warn. This is to help
441 users who forget the C<is> option. If you really do not want any accessors,
442 you can use C<< is => 'bare' >>. You can maintain back compat with older
443 versions of Moose by using something like:
445 ($Moose::VERSION >= 0.84 ? is => 'bare' : ())
447 When an accessor overwrites an existing method, we now warn. To work around
448 this warning (if you really must have this behavior), you can explicitly
449 remove the method before creating it as an accessor:
453 __PACKAGE__->meta->remove_method('foo');
459 When an unknown option is passed to C<has>, we now warn. You can silence
460 the warning by fixing your code. :)
462 The C<Role> type has been deprecated. On its own, it was useless,
463 since it just checked C<< $object->can('does') >>. If you were using
464 it as a parent type, just call C<role_type('Role::Name')> to create an
465 appropriate type instead.
469 C<use Moose::Exporter;> now imports C<strict> and C<warnings> into packages
474 C<DEMOLISHALL> and C<DEMOLISH> now receive an argument indicating whether or
475 not we are in global destruction.
479 Type constraints no longer run coercions for a value that already matches the
480 constraint. This may affect some (arguably buggy) edge case coercions that
481 rely on side effects in the C<via> clause.
485 L<Moose::Exporter> now accepts the C<-metaclass> option for easily
486 overriding the metaclass (without L<metaclass>). This works for classes
491 Added a C<duck_type> sugar function to L<Moose::Util::TypeConstraints>
492 to make integration with non-Moose classes easier. It simply checks if
493 C<< $obj->can() >> a list of methods.
495 A number of methods (mostly inherited from L<Class::MOP>) have been
496 renamed with a leading underscore to indicate their internal-ness. The
497 old method names will still work for a while, but will warn that the
498 method has been renamed. In a few cases, the method will be removed
499 entirely in the future. This may affect MooseX authors who were using
504 Calling C<subtype> with a name as the only argument now throws an
505 exception. If you want an anonymous subtype do:
507 my $subtype = subtype as 'Foo';
509 This is related to the changes in version 0.71_01.
511 The C<is_needed> method in L<Moose::Meta::Method::Destructor> is now
512 only usable as a class method. Previously, it worked as a class or
513 object method, with a different internal implementation for each
516 The internals of making a class immutable changed a lot in Class::MOP
517 0.78_02, and Moose's internals have changed along with it. The
518 external C<< $metaclass->make_immutable >> method still works the same
523 A mutable class accepted C<< Foo->new(undef) >> without complaint,
524 while an immutable class would blow up with an unhelpful error. Now,
525 in both cases we throw a helpful error instead.
527 This "feature" was originally added to allow for cases such as this:
535 return My::Class->new($args);
537 But we decided this is a bad idea and a little too magical, because it
538 can easily mask real errors.
542 Calling C<type> or C<subtype> without the sugar helpers (C<as>,
543 C<where>, C<message>) is now deprecated.
545 As a side effect, this meant we ended up using Perl prototypes on
546 C<as>, and code like this will no longer work:
548 use Moose::Util::TypeConstraints;
549 use Declare::Constraints::Simple -All;
551 subtype 'ArrayOfInts'
553 => IsArrayRef(IsInt);
555 Instead it must be changed to this:
560 where => IsArrayRef(IsInt)
564 If you want to maintain backwards compat with older versions of Moose,
565 you must explicitly test Moose's C<VERSION>:
567 if ( Moose->VERSION < 0.71_01 ) {
568 subtype 'ArrayOfInts'
570 => IsArrayRef(IsInt);
576 where => IsArrayRef(IsInt)
583 We no longer pass the meta-attribute object as a final argument to
584 triggers. This actually changed for inlined code a while back, but the
585 non-inlined version and the docs were still out of date.
587 If by some chance you actually used this feature, the workaround is
588 simple. You fetch the attribute object from out of the C<$self>
589 that is passed as the first argument to trigger, like so:
595 my ( $self, $value ) = @_;
596 my $attr = $self->meta->find_attribute_by_name('foo');
604 If you created a subtype and passed a parent that Moose didn't know
605 about, it simply ignored the parent. Now it automatically creates the
606 parent as a class type. This may not be what you want, but is less
609 You could declare a name with subtype such as "Foo!Bar". Moose would
610 accept this allowed, but if you used it in a parameterized type such
611 as "ArrayRef[Foo!Bar]" it wouldn't work. We now do some vetting on
612 names created via the sugar functions, so that they can only contain
613 alphanumerics, ":", and ".".
617 Methods created via an attribute can now fulfill a C<requires>
618 declaration for a role. Honestly we don't know why Stevan didn't make
619 this work originally, he was just insane or something.
621 Stack traces from inlined code will now report the line and file as
622 being in your class, as opposed to in Moose guts.
626 When a class does not provide all of a role's required methods, the
627 error thrown now mentions all of the missing methods, as opposed to
628 just the first missing method.
630 Moose will no longer inline a constructor for your class unless it
631 inherits its constructor from Moose::Object, and will warn when it
632 doesn't inline. If you want to force inlining anyway, pass
633 C<< replace_constructor => 1 >> to C<make_immutable>.
635 If you want to get rid of the warning, pass C<< inline_constructor =>
640 Removed the (deprecated) C<make_immutable> keyword.
642 Removing an attribute from a class now also removes delegation
643 (C<handles>) methods installed for that attribute. This is correct
644 behavior, but if you were wrongly relying on it you might get bit.
648 Roles now add methods by calling C<add_method>, not
649 C<alias_method>. They make sure to always provide a method object,
650 which will be cloned internally. This means that it is now possible to
651 track the source of a method provided by a role, and even follow its
652 history through intermediate roles. This means that methods added by
653 a role now show up when looking at a class's method list/map.
655 Parameter and Union args are now sorted, this makes Int|Str the same
656 constraint as Str|Int. Also, incoming type constraint strings are
657 normalized to remove all whitespace differences. This is mostly for
658 internals and should not affect outside code.
660 L<Moose::Exporter> will no longer remove a subroutine that the
661 exporting package re-exports. Moose re-exports the Carp::confess
662 function, among others. The reasoning is that we cannot know whether
663 you have also explicitly imported those functions for your own use, so
664 we err on the safe side and always keep them.
668 C<Moose::init_meta> should now be called as a method.
670 New modules for extension writers, L<Moose::Exporter> and
671 L<Moose::Util::MetaRole>.
675 Implemented metaclass traits (and wrote a recipe for it):
677 use Moose -traits => 'Foo'
679 This should make writing small Moose extensions a little
684 Fixed C<coerce> to accept anon types just like C<subtype> can.
687 coerce $some_anon_type => from 'Str' => via { ... };
691 Added C<BUILDARGS>, a new step in C<< Moose::Object->new() >>.
695 Fixed how the C<< is => (ro|rw) >> works with custom defined
696 C<reader>, C<writer> and C<accessor> options. See the below table for
699 is => ro, writer => _foo # turns into (reader => foo, writer => _foo)
700 is => rw, writer => _foo # turns into (reader => foo, writer => _foo)
701 is => rw, accessor => _foo # turns into (accessor => _foo)
702 is => ro, accessor => _foo # error, accesor is rw
706 The C<before/around/after> method modifiers now support regexp
707 matching of method names. NOTE: this only works for classes, it is
708 currently not supported in roles, but, ... patches welcome.
710 The C<has> keyword for roles now accepts the same array ref form that
711 L<Moose>.pm does for classes.
713 A trigger on a read-only attribute is no longer an error, as it's
714 useful to trigger off of the constructor.
716 Subtypes of parameterizable types now are parameterizable types
721 Fixed issue where C<DEMOLISHALL> was eating the value in C<$@>, and so
722 not working correctly. It still kind of eats them, but so does vanilla
727 Inherited attributes may now be extended without restriction on the
728 type ('isa', 'does').
730 The entire set of Moose::Meta::TypeConstraint::* classes were
731 refactored in this release. If you were relying on their internals you
732 should test your code carefully.
736 Documenting the use of '+name' with attributes that come from recently
737 composed roles. It makes sense, people are using it, and so why not
738 just officially support it.
740 The C<< Moose::Meta::Class->create >> method now supports roles.
742 It is now possible to make anonymous enum types by passing C<enum> an
743 array reference instead of the C<< enum $name => @values >>.
747 Added the C<make_immutable> keyword as a shortcut to calling
748 C<make_immutable> on the meta object. This eventually got removed!
750 Made C<< init_arg => undef >> work in Moose. This means "do not accept
751 a constructor parameter for this attribute".
753 Type errors now use the provided message. Prior to this release they
758 Moose is now a postmodern object system :)
760 The Role system was completely refactored. It is 100% backwards
761 compat, but the internals were totally changed. If you relied on the
762 internals then you are advised to test carefully.
764 Added method exclusion and aliasing for Roles in this release.
766 Added the L<Moose::Util::TypeConstraints::OptimizedConstraints>
769 Passing a list of values to an accessor (which is only expecting one
770 value) used to be silently ignored, now it throws an error.
774 Added parameterized types and did a pretty heavy refactoring of the
775 type constraint system.
777 Better framework extendability and better support for "making your own
780 =head1 0.25 or before
782 Honestly, you shouldn't be using versions of Moose that are this old,
783 so many bug fixes and speed improvements have been made you would be
784 crazy to not upgrade.
786 Also, I am tired of going through the Changelog so I am stopping here,
787 if anyone would like to continue this please feel free.
791 Stevan Little E<lt>stevan@iinteractive.comE<gt>
793 =head1 COPYRIGHT AND LICENSE
795 Copyright 2009 by Infinity Interactive, Inc.
797 L<http://www.iinteractive.com>
799 This library is free software; you can redistribute it and/or modify
800 it under the same terms as Perl itself.