1 package Moose::Manual::Delta;
3 # ABSTRACT: Important Changes in Moose
11 This documents any important or noteworthy changes in Moose, with a
12 focus on backwards. This does duplicate data from the F<Changes> file,
13 but aims to provide more details and when possible workarounds.
15 Besides helping keep up with changes, you can also use this document
16 for finding the lowest version of Moose that supported a given
17 feature. If you encounter a problem and have a solution but don't see
18 it documented here, or think we missed an important feature, please
25 =item Roles have their own default attribute metaclass
27 Previously, when a role was applied to a class, it would use the attribute
28 metaclass defined in the class when copying over the attributes in the role.
29 This was wrong, because for instance, using L<MooseX::FollowPBP> in the class
30 would end up renaming all of the accessors generated by the role, some of which
31 may be being called in the role, causing it to break. Roles now keep track of
32 their own attribute metaclass to use by default when being applied to a class
33 (defaulting to Moose::Meta::Attribute). This is modifiable using
34 L<Moose::Util::MetaRole> by passing the C<applied_attribute> key to the
35 C<role_metaroles> option, as in:
37 Moose::Util::MetaRole::apply_metaroles(
40 attribute => ['My::Meta::Role::Attribute'],
43 applied_attribute => ['My::Meta::Role::Attribute'],
53 =item Configurable stacktraces
55 Classes which use the L<Moose::Error::Default> error class can now have
56 stacktraces disabled by setting the C<MOOSE_ERROR_STYLE> env var to C<croak>.
57 This is experimental, fairly incomplete, and won't work in all cases (because
58 Moose's error system in general is all of these things), but this should allow
59 for reducing at least some of the verbosity in most cases.
67 =item Native Delegations
69 In previous versions of Moose, the Native delegations were created as
70 closures. The generated code was often quite slow compared to doing the same
71 thing by hand. For example, the Array's push delegation ended up doing
74 push @{ $self->$reader() }, @_;
76 If the attribute was created without a reader, the C<$reader> sub reference
77 followed a very slow code path. Even with a reader, this is still slower than
80 Native delegations are now generated as inline code, just like other
81 accessors, so we can access the slot directly.
83 In addition, native traits now do proper constraint checking in all cases. In
84 particular, constraint checking has been improved for array and hash
85 references. Previously, only the I<contained> type (the C<Str> in
86 C<HashRef[Str]>) would be checked when a new value was added to the
87 collection. However, if there was a constraint that applied to the whole
88 value, this was never checked.
90 In addition, coercions are now called on the whole value.
92 The delegation methods now do more argument checking. All of the methods check
93 that a valid number of arguments were passed to the method. In addition, the
94 delegation methods check that the arguments are sane (array indexes, hash
95 keys, numbers, etc.) when applicable. We have tried to emulate the behavior of
96 Perl builtins as much as possible.
98 Finally, triggers are called whenever the value of the attribute is changed by
101 These changes are only likely to break code in a few cases.
103 The inlining code may or may not preserve the original reference when changes
104 are made. In some cases, methods which change the value may replace it
105 entirely. This will break tied values.
107 If you have a typed arrayref or hashref attribute where the type enforces a
108 constraint on the whole collection, this constraint will now be checked. It's
109 possible that code which previously ran without errors will now cause the
110 constraint to fail. However, presumably this is a good thing ;)
112 If you are passing invalid arguments to a delegation which were previously
113 being ignored, these calls will now fail.
115 If your code relied on the trigger only being called for a regular writer,
116 that may cause problems.
118 As always, you are encouraged to test before deploying the latest version of
121 =item Defaults is and default for String, Counter, and Bool
123 A few native traits (String, Counter, Bool) provide default values of "is" and
124 "default" when you created an attribute. Allowing them to provide these values
125 is now deprecated. Supply the value yourself when creating the attribute.
127 =item The C<meta> method
129 Moose and Class::MOP have been cleaned up internally enough to make the
130 C<meta> method that you get by default optional. C<use Moose> and
131 C<use Moose::Role> now can take an additional C<-meta_name> option, which
132 tells Moose what name to use when installing the C<meta> method. Passing
133 C<undef> to this option suppresses generation of the C<meta> method
134 entirely. This should be useful for users of modules which also use a C<meta>
135 method or function, such as L<Curses> or L<Rose::DB::Object>.
143 =item All deprecated features now warn
145 Previously, deprecation mostly consisted of simply saying "X is deprecated" in
146 the Changes file. We were not very consistent about actually warning. Now, all
147 deprecated features still present in Moose actually give a warning. The
148 warning is issued once per calling package. See L<Moose::Deprecated> for more
151 =item You cannot pass C<< coerce => 1 >> unless the attribute's type constraint has a coercion
153 Previously, this was accepted, and it sort of worked, except that if you
154 attempted to set the attribute after the object was created, you would get a
157 Now you will get a warning when you attempt to define the attribute.
159 =item C<no Moose>, C<no Moose::Role>, and C<no Moose::Exporter> no longer unimport strict and warnings
161 This change was made in 1.05, and has now been reverted. We don't know if the
162 user has explicitly loaded strict or warnings on their own, and unimporting
163 them is just broken in that case.
165 =item Reversed logic when defining which options can be changed
167 L<Moose::Meta::Attribute> now allows all options to be changed in an
168 overridden attribute. The previous behaviour required each option to be
169 whitelisted using the C<legal_options_for_inheritance> method. This method has
170 been removed, and there is a new method, C<illegal_options_for_inheritance>,
171 which can now be used to prevent certain options from being changeable.
173 In addition, we only throw an error if the illegal option is actually
174 changed. If the superclass didn't specify this option at all when defining the
175 attribute, the subclass version can still add it as an option.
177 Example of overriding this in an attribute trait:
179 package Bar::Meta::Attribute;
182 has 'my_illegal_option' => (
187 around illegal_options_for_inheritance => sub {
188 return ( shift->(@_), qw/my_illegal_option/ );
197 =item L<Moose::Object/BUILD> methods are now called when calling C<new_object>
199 Previously, C<BUILD> methods would only be called from C<Moose::Object::new>,
200 but now they are also called when constructing an object via
201 C<Moose::Meta::Class::new_object>. C<BUILD> methods are an inherent part of the
202 object construction process, and this should make C<< $meta->new_object >>
203 actually usable without forcing people to use C<< $meta->name->new >>.
205 =item C<no Moose>, C<no Moose::Role>, and C<no Moose::Exporter> now unimport strict and warnings
207 In the interest of having C<no Moose> clean up everything that C<use Moose>
208 does in the calling scope, C<no Moose> (as well as all other
209 L<Moose::Exporter>-using modules) now unimports strict and warnings.
211 =item Metaclass compatibility checking and fixing should be much more robust
213 The L<metaclass compatibility|Moose/METACLASS COMPATIBILITY AND MOOSE> checking
214 and fixing algorithms have been completely rewritten, in both Class::MOP and
215 Moose. This should resolve many confusing errors when dealing with non-Moose
216 inheritance and with custom metaclasses for things like attributes,
217 constructors, etc. For correct code, the only thing that should require a
218 change is that custom error metaclasses must now inherit from
219 L<Moose::Error::Default>.
227 =item Moose::Meta::TypeConstraint::Class is_subtype_of behavior
229 Earlier versions of L<is_subtype_of|Moose::Meta::TypeConstraint::Class/is_subtype_of>
230 would incorrectly return true when called with itself, its own TC name or
231 its class name as an argument. (i.e. $foo_tc->is_subtype_of('Foo') == 1) This
232 behavior was a caused by C<isa> being checked before the class name. The old
233 behavior can be accessed with L<is_type_of|Moose::Meta::TypeConstraint::Class/is_type_of>
241 =item Moose::Meta::Attribute::Native::Trait::Code no longer creates reader methods by default
243 Earlier versions of L<Moose::Meta::Attribute::Native::Trait::Code> created
244 read-only accessors for the attributes it's been applied to, even if you didn't
245 ask for it with C<< is => 'ro' >>. This incorrect behaviour has now been fixed.
253 =item Moose::Util add_method_modifier behavior
255 add_method_modifier (and subsequently the sugar functions Moose::before,
256 Moose::after, and Moose::around) can now accept arrayrefs, with the same
257 behavior as lists. Types other than arrayref and regexp result in an error.
261 =head1 0.93_01 and 0.94
265 =item Moose::Util::MetaRole API has changed
267 The C<apply_metaclass_roles> function is now called C<apply_metaroles>. The
268 way arguments are supplied has been changed to force you to distinguish
269 between metaroles applied to L<Moose::Meta::Class> (and helpers) versus
270 L<Moose::Meta::Role>.
272 The old API still works, but will warn in a future release, and eventually be
275 =item Moose::Meta::Role has real attributes
277 The attributes returned by L<Moose::Meta::Role> are now instances of the
278 L<Moose::Meta::Role::Attribute> class, instead of bare hash references.
280 =item "no Moose" now removes C<blessed> and C<confess>
282 Moose is now smart enough to know exactly what it exported, even when it
283 re-exports functions from other packages. When you unimport Moose, it will
284 remove these functions from your namespace unless you I<also> imported them
285 directly from their respective packages.
287 If you have a C<no Moose> in your code I<before> you call C<blessed> or
288 C<confess>, your code will break. You can either move the C<no Moose> call
289 later in your code, or explicitly import the relevant functions from the
290 packages that provide them.
292 =item L<Moose::Exporter> is smarter about unimporting re-exports
294 The change above comes from a general improvement to L<Moose::Exporter>. It
295 will now unimport any function it exports, even if that function is a
296 re-export from another package.
298 =item Attributes in roles can no longer override class attributes with "+foo"
300 Previously, this worked more or less accidentally, because role attributes
301 weren't objects. This was never documented, but a few MooseX modules took
304 =item The composition_class_roles attribute in L<Moose::Meta::Role> is now a method
306 This was done to make it possible for roles to alter the the list of
307 composition class roles by applying a method modifiers. Previously, this was
308 an attribute and MooseX modules override it. Since that no longer works, this
311 This I<should> be an attribute, so this may switch back to being an attribute
312 in the future if we can figure out how to make this work.
320 =item Calling $object->new() is no longer deprecated
322 We decided to undeprecate this. Now it just works.
324 =item Both C<get_method_map> and C<get_attribute_map> is deprecated
326 These metaclass methods were never meant to be public, and they are both now
327 deprecated. The work around if you still need the functionality they provided
328 is to iterate over the list of names manually.
330 my %fields = map { $_ => $meta->get_attribute($_) } $meta->get_attribute_list;
332 This was actually a change in L<Class::MOP>, but this version of Moose
333 requires a version of L<Class::MOP> that includes said change.
341 =item Added Native delegation for Code refs
343 See L<Moose::Meta::Attribute::Native::Trait::Code> for details.
345 =item Calling $object->new() is deprecated
347 Moose has long supported this, but it's never really been documented, and we
348 don't think this is a good practice. If you want to construct an object from
349 an existing object, you should provide some sort of alternate constructor like
350 C<< $object->clone >>.
352 Calling C<< $object->new >> now issues a warning, and will be an error in a
355 =item Moose no longer warns if you call C<make_immutable> for a class with mutable ancestors
357 While in theory this is a good thing to warn about, we found so many
358 exceptions to this that doing this properly became quite problematic.
366 =item New Native delegation methods from L<List::Util> and L<List::MoreUtils>
368 In particular, we now have C<reduce>, C<shuffle>, C<uniq>, and C<natatime>.
370 =item The Moose::Exporter with_caller feature is now deprecated
372 Use C<with_meta> instead. The C<with_caller> option will start warning in a
375 =item Moose now warns if you call C<make_immutable> for a class with mutable ancestors
377 This is dangerous because modifying a class after a subclass has been
378 immutabilized will lead to incorrect results in the subclass, due to inlining,
379 caching, etc. This occasionally happens accidentally, when a class loads one
380 of its subclasses in the middle of its class definition, so pointing out that
381 this may cause issues should be helpful. Metaclasses (classes that inherit
382 from L<Class::MOP::Object>) are currently exempt from this check, since at the
383 moment we aren't very consistent about which metaclasses we immutabilize.
385 =item C<enum> and C<duck_type> now take arrayrefs for all forms
387 Previously, calling these functions with a list would take the first element of
388 the list as the type constraint name, and use the remainder as the enum values
389 or method names. This makes the interface inconsistent with the anon-type forms
390 of these functions (which must take an arrayref), and a free-form list where
391 the first value is sometimes special is hard to validate (and harder to give
392 reasonable error messages for). These functions have been changed to take
393 arrayrefs in all their forms - so, C<< enum 'My::Type' => [qw(foo bar)] >> is
394 now the preferred way to create an enum type constraint. The old syntax still
395 works for now, but it will hopefully be deprecated and removed in a future
402 L<Moose::Meta::Attribute::Native> has been moved into the Moose core from
403 L<MooseX::AttributeHelpers>. Major changes include:
407 =item C<traits>, not C<metaclass>
409 Method providers are only available via traits.
411 =item C<handles>, not C<provides> or C<curries>
413 The C<provides> syntax was like core Moose C<< handles => HASHREF >>
414 syntax, but with the keys and values reversed. This was confusing,
415 and AttributeHelpers now uses C<< handles => HASHREF >> in a way that
416 should be intuitive to anyone already familiar with how it is used for
419 The C<curries> functionality provided by AttributeHelpers has been
420 generalized to apply to all cases of C<< handles => HASHREF >>, though
421 not every piece of functionality has been ported (currying with a
422 CODEREF is not supported).
424 =item C<empty> is now C<is_empty>, and means empty, not non-empty
426 Previously, the C<empty> method provided by Arrays and Hashes returned true if
427 the attribute was B<not> empty (no elements). Now it returns true if the
428 attribute B<is> empty. It was also renamed to C<is_empty>, to reflect this.
430 =item C<find> was renamed to C<first>, and C<first> and C<last> were removed
432 L<List::Util> refers to the functionality that we used to provide under C<find>
433 as L<first|List::Util/first>, so that will likely be more familiar (and will
434 fit in better if we decide to add more List::Util functions). C<first> and
435 C<last> were removed, since their functionality is easily duplicated with
438 =item Helpers that take a coderef of one argument now use C<$_>
440 Subroutines passed as the first argument to C<first>, C<map>, and C<grep> now
441 receive their argument in C<$_> rather than as a parameter to the subroutine.
442 Helpers that take a coderef of two or more arguments remain using the argument
443 list (there are technical limitations to using C<$a> and C<$b> like C<sort>
446 See L<Moose::Meta::Attribute::Native> for the new documentation.
450 The C<alias> and C<excludes> role parameters have been renamed to C<-alias>
451 and C<-excludes>. The old names still work, but new code should use the new
452 names, and eventually the old ones will be deprecated and removed.
456 C<< use Moose -metaclass => 'Foo' >> now does alias resolution, just like
457 C<-traits> (and the C<metaclass> and C<traits> options to C<has>).
459 Added two functions C<meta_class_alias> and C<meta_attribute_alias> to
460 L<Moose::Util>, to simplify aliasing metaclasses and metatraits. This is
461 a wrapper around the old
463 package Moose::Meta::Class::Custom::Trait::FooTrait;
464 sub register_implementation { 'My::Meta::Trait' }
470 When an attribute generates I<no> accessors, we now warn. This is to help
471 users who forget the C<is> option. If you really do not want any accessors,
472 you can use C<< is => 'bare' >>. You can maintain back compat with older
473 versions of Moose by using something like:
475 ($Moose::VERSION >= 0.84 ? is => 'bare' : ())
477 When an accessor overwrites an existing method, we now warn. To work around
478 this warning (if you really must have this behavior), you can explicitly
479 remove the method before creating it as an accessor:
483 __PACKAGE__->meta->remove_method('foo');
489 When an unknown option is passed to C<has>, we now warn. You can silence
490 the warning by fixing your code. :)
492 The C<Role> type has been deprecated. On its own, it was useless,
493 since it just checked C<< $object->can('does') >>. If you were using
494 it as a parent type, just call C<role_type('Role::Name')> to create an
495 appropriate type instead.
499 C<use Moose::Exporter;> now imports C<strict> and C<warnings> into packages
504 C<DEMOLISHALL> and C<DEMOLISH> now receive an argument indicating whether or
505 not we are in global destruction.
509 Type constraints no longer run coercions for a value that already matches the
510 constraint. This may affect some (arguably buggy) edge case coercions that
511 rely on side effects in the C<via> clause.
515 L<Moose::Exporter> now accepts the C<-metaclass> option for easily
516 overriding the metaclass (without L<metaclass>). This works for classes
521 Added a C<duck_type> sugar function to L<Moose::Util::TypeConstraints>
522 to make integration with non-Moose classes easier. It simply checks if
523 C<< $obj->can() >> a list of methods.
525 A number of methods (mostly inherited from L<Class::MOP>) have been
526 renamed with a leading underscore to indicate their internal-ness. The
527 old method names will still work for a while, but will warn that the
528 method has been renamed. In a few cases, the method will be removed
529 entirely in the future. This may affect MooseX authors who were using
534 Calling C<subtype> with a name as the only argument now throws an
535 exception. If you want an anonymous subtype do:
537 my $subtype = subtype as 'Foo';
539 This is related to the changes in version 0.71_01.
541 The C<is_needed> method in L<Moose::Meta::Method::Destructor> is now
542 only usable as a class method. Previously, it worked as a class or
543 object method, with a different internal implementation for each
546 The internals of making a class immutable changed a lot in Class::MOP
547 0.78_02, and Moose's internals have changed along with it. The
548 external C<< $metaclass->make_immutable >> method still works the same
553 A mutable class accepted C<< Foo->new(undef) >> without complaint,
554 while an immutable class would blow up with an unhelpful error. Now,
555 in both cases we throw a helpful error instead.
557 This "feature" was originally added to allow for cases such as this:
565 return My::Class->new($args);
567 But we decided this is a bad idea and a little too magical, because it
568 can easily mask real errors.
572 Calling C<type> or C<subtype> without the sugar helpers (C<as>,
573 C<where>, C<message>) is now deprecated.
575 As a side effect, this meant we ended up using Perl prototypes on
576 C<as>, and code like this will no longer work:
578 use Moose::Util::TypeConstraints;
579 use Declare::Constraints::Simple -All;
581 subtype 'ArrayOfInts'
583 => IsArrayRef(IsInt);
585 Instead it must be changed to this:
590 where => IsArrayRef(IsInt)
594 If you want to maintain backwards compat with older versions of Moose,
595 you must explicitly test Moose's C<VERSION>:
597 if ( Moose->VERSION < 0.71_01 ) {
598 subtype 'ArrayOfInts'
600 => IsArrayRef(IsInt);
606 where => IsArrayRef(IsInt)
613 We no longer pass the meta-attribute object as a final argument to
614 triggers. This actually changed for inlined code a while back, but the
615 non-inlined version and the docs were still out of date.
617 If by some chance you actually used this feature, the workaround is
618 simple. You fetch the attribute object from out of the C<$self>
619 that is passed as the first argument to trigger, like so:
625 my ( $self, $value ) = @_;
626 my $attr = $self->meta->find_attribute_by_name('foo');
634 If you created a subtype and passed a parent that Moose didn't know
635 about, it simply ignored the parent. Now it automatically creates the
636 parent as a class type. This may not be what you want, but is less
639 You could declare a name with subtype such as "Foo!Bar". Moose would
640 accept this allowed, but if you used it in a parameterized type such
641 as "ArrayRef[Foo!Bar]" it wouldn't work. We now do some vetting on
642 names created via the sugar functions, so that they can only contain
643 alphanumerics, ":", and ".".
647 Methods created via an attribute can now fulfill a C<requires>
648 declaration for a role. Honestly we don't know why Stevan didn't make
649 this work originally, he was just insane or something.
651 Stack traces from inlined code will now report the line and file as
652 being in your class, as opposed to in Moose guts.
656 When a class does not provide all of a role's required methods, the
657 error thrown now mentions all of the missing methods, as opposed to
658 just the first missing method.
660 Moose will no longer inline a constructor for your class unless it
661 inherits its constructor from Moose::Object, and will warn when it
662 doesn't inline. If you want to force inlining anyway, pass
663 C<< replace_constructor => 1 >> to C<make_immutable>.
665 If you want to get rid of the warning, pass C<< inline_constructor =>
670 Removed the (deprecated) C<make_immutable> keyword.
672 Removing an attribute from a class now also removes delegation
673 (C<handles>) methods installed for that attribute. This is correct
674 behavior, but if you were wrongly relying on it you might get bit.
678 Roles now add methods by calling C<add_method>, not
679 C<alias_method>. They make sure to always provide a method object,
680 which will be cloned internally. This means that it is now possible to
681 track the source of a method provided by a role, and even follow its
682 history through intermediate roles. This means that methods added by
683 a role now show up when looking at a class's method list/map.
685 Parameter and Union args are now sorted, this makes Int|Str the same
686 constraint as Str|Int. Also, incoming type constraint strings are
687 normalized to remove all whitespace differences. This is mostly for
688 internals and should not affect outside code.
690 L<Moose::Exporter> will no longer remove a subroutine that the
691 exporting package re-exports. Moose re-exports the Carp::confess
692 function, among others. The reasoning is that we cannot know whether
693 you have also explicitly imported those functions for your own use, so
694 we err on the safe side and always keep them.
698 C<Moose::init_meta> should now be called as a method.
700 New modules for extension writers, L<Moose::Exporter> and
701 L<Moose::Util::MetaRole>.
705 Implemented metaclass traits (and wrote a recipe for it):
707 use Moose -traits => 'Foo'
709 This should make writing small Moose extensions a little
714 Fixed C<coerce> to accept anon types just like C<subtype> can.
717 coerce $some_anon_type => from 'Str' => via { ... };
721 Added C<BUILDARGS>, a new step in C<< Moose::Object->new() >>.
725 Fixed how the C<< is => (ro|rw) >> works with custom defined
726 C<reader>, C<writer> and C<accessor> options. See the below table for
729 is => ro, writer => _foo # turns into (reader => foo, writer => _foo)
730 is => rw, writer => _foo # turns into (reader => foo, writer => _foo)
731 is => rw, accessor => _foo # turns into (accessor => _foo)
732 is => ro, accessor => _foo # error, accesor is rw
736 The C<before/around/after> method modifiers now support regexp
737 matching of method names. NOTE: this only works for classes, it is
738 currently not supported in roles, but, ... patches welcome.
740 The C<has> keyword for roles now accepts the same array ref form that
741 L<Moose>.pm does for classes.
743 A trigger on a read-only attribute is no longer an error, as it's
744 useful to trigger off of the constructor.
746 Subtypes of parameterizable types now are parameterizable types
751 Fixed issue where C<DEMOLISHALL> was eating the value in C<$@>, and so
752 not working correctly. It still kind of eats them, but so does vanilla
757 Inherited attributes may now be extended without restriction on the
758 type ('isa', 'does').
760 The entire set of Moose::Meta::TypeConstraint::* classes were
761 refactored in this release. If you were relying on their internals you
762 should test your code carefully.
766 Documenting the use of '+name' with attributes that come from recently
767 composed roles. It makes sense, people are using it, and so why not
768 just officially support it.
770 The C<< Moose::Meta::Class->create >> method now supports roles.
772 It is now possible to make anonymous enum types by passing C<enum> an
773 array reference instead of the C<< enum $name => @values >>.
777 Added the C<make_immutable> keyword as a shortcut to calling
778 C<make_immutable> on the meta object. This eventually got removed!
780 Made C<< init_arg => undef >> work in Moose. This means "do not accept
781 a constructor parameter for this attribute".
783 Type errors now use the provided message. Prior to this release they
788 Moose is now a postmodern object system :)
790 The Role system was completely refactored. It is 100% backwards
791 compat, but the internals were totally changed. If you relied on the
792 internals then you are advised to test carefully.
794 Added method exclusion and aliasing for Roles in this release.
796 Added the L<Moose::Util::TypeConstraints::OptimizedConstraints>
799 Passing a list of values to an accessor (which is only expecting one
800 value) used to be silently ignored, now it throws an error.
804 Added parameterized types and did a pretty heavy refactoring of the
805 type constraint system.
807 Better framework extensibility and better support for "making your own
810 =head1 0.25 or before
812 Honestly, you shouldn't be using versions of Moose that are this old,
813 so many bug fixes and speed improvements have been made you would be
814 crazy to not upgrade.
816 Also, I am tired of going through the Changelog so I am stopping here,
817 if anyone would like to continue this please feel free.