package Role::Tiny;
sub _getglob { \*{$_[0]} }
sub _getstash { \%{"$_[0]::"} }
use strict;
use warnings;
our $VERSION = '2.000000';
$VERSION = eval $VERSION;
our %INFO;
our %APPLIED_TO;
our %COMPOSED;
our %COMPOSITE_INFO;
our @ON_ROLE_CREATE;
# Module state workaround totally stolen from Zefram's Module::Runtime.
BEGIN {
*_WORK_AROUND_BROKEN_MODULE_STATE = "$]" < 5.009 ? sub(){1} : sub(){0};
*_MRO_MODULE = "$]" < 5.010 ? sub(){"MRO/Compat.pm"} : sub(){"mro.pm"};
}
sub Role::Tiny::__GUARD__::DESTROY {
delete $INC{$_[0]->[0]} if @{$_[0]};
}
sub _load_module {
(my $proto = $_[0]) =~ s/::/\//g;
$proto .= '.pm';
return 1 if $INC{$proto};
# can't just ->can('can') because a sub-package Foo::Bar::Baz
# creates a 'Baz::' key in Foo::Bar's symbol table
return 1 if grep !/::$/, keys %{_getstash($_[0])||{}};
my $guard = _WORK_AROUND_BROKEN_MODULE_STATE
&& bless([ $proto ], 'Role::Tiny::__GUARD__');
require $proto;
pop @$guard if _WORK_AROUND_BROKEN_MODULE_STATE;
return 1;
}
sub import {
my $target = caller;
my $me = shift;
strict->import;
warnings->import;
return if $me->is_role($target); # already exported into this package
$INFO{$target}{is_role} = 1;
# get symbol table reference
my $stash = _getstash($target);
# install before/after/around subs
foreach my $type (qw(before after around)) {
*{_getglob "${target}::${type}"} = sub {
require Class::Method::Modifiers;
push @{$INFO{$target}{modifiers}||=[]}, [ $type => @_ ];
return;
};
}
*{_getglob "${target}::requires"} = sub {
push @{$INFO{$target}{requires}||=[]}, @_;
return;
};
*{_getglob "${target}::with"} = sub {
$me->apply_roles_to_package($target, @_);
return;
};
# grab all *non-constant* (stash slot is not a scalarref) subs present
# in the symbol table and store their refaddrs (no need to forcibly
# inflate constant subs into real subs) with a map to the coderefs in
# case of copying or re-use
my @not_methods = (map { *$_{CODE}||() } grep !ref($_), values %$stash);
@{$INFO{$target}{not_methods}={}}{@not_methods} = @not_methods;
# a role does itself
$APPLIED_TO{$target} = { $target => undef };
$_->($target) for @ON_ROLE_CREATE;
}
sub role_application_steps {
qw(_install_methods _check_requires _install_modifiers _copy_applied_list);
}
sub apply_single_role_to_package {
my ($me, $to, $role) = @_;
_load_module($role);
die "This is apply_role_to_package" if ref($to);
die "${role} is not a Role::Tiny" unless $me->is_role($role);
foreach my $step ($me->role_application_steps) {
$me->$step($to, $role);
}
}
sub _copy_applied_list {
my ($me, $to, $role) = @_;
# copy our role list into the target's
@{$APPLIED_TO{$to}||={}}{keys %{$APPLIED_TO{$role}}} = ();
}
sub apply_roles_to_object {
my ($me, $object, @roles) = @_;
die "No roles supplied!" unless @roles;
my $class = ref($object);
# on perl < 5.8.9, magic isn't copied to all ref copies. bless the parameter
# directly, so at least the variable passed to us will get any magic applied
bless($_[1], $me->create_class_with_roles($class, @roles));
}
my $role_suffix = 'A000';
sub _composite_name {
my ($me, $superclass, @roles) = @_;
my $new_name = join(
'__WITH__', $superclass, my $compose_name = join '__AND__', @roles
);
if (length($new_name) > 252) {
$new_name = $COMPOSED{abbrev}{$new_name}
||= substr($new_name, 0, 250 - length $role_suffix).'__'.$role_suffix++;
}
return wantarray ? ($new_name, $compose_name) : $new_name;
}
sub create_class_with_roles {
my ($me, $superclass, @roles) = @_;
die "No roles supplied!" unless @roles;
_load_module($superclass);
{
my %seen;
$seen{$_}++ for @roles;
if (my @dupes = grep $seen{$_} > 1, @roles) {
die "Duplicated roles: ".join(', ', @dupes);
}
}
my ($new_name, $compose_name) = $me->_composite_name($superclass, @roles);
return $new_name if $COMPOSED{class}{$new_name};
foreach my $role (@roles) {
_load_module($role);
die "${role} is not a Role::Tiny" unless $me->is_role($role);
}
require(_MRO_MODULE);
my $composite_info = $me->_composite_info_for(@roles);
my %conflicts = %{$composite_info->{conflicts}};
if (keys %conflicts) {
my $fail =
join "\n",
map {
"Method name conflict for '$_' between roles "
."'".join(' and ', sort values %{$conflicts{$_}})."'"
.", cannot apply these simultaneously to an object."
} keys %conflicts;
die $fail;
}
my @composable = map $me->_composable_package_for($_), reverse @roles;
# some methods may not exist in the role, but get generated by
# _composable_package_for (Moose accessors via Moo). filter out anything
# provided by the composable packages, excluding the subs we generated to
# make modifiers work.
my @requires = grep {
my $method = $_;
!grep $_->can($method) && !$COMPOSED{role}{$_}{modifiers_only}{$method},
@composable
} @{$composite_info->{requires}};
$me->_check_requires(
$superclass, $compose_name, \@requires
);
*{_getglob("${new_name}::ISA")} = [ @composable, $superclass ];
@{$APPLIED_TO{$new_name}||={}}{
map keys %{$APPLIED_TO{$_}}, @roles
} = ();
$COMPOSED{class}{$new_name} = 1;
return $new_name;
}
# preserved for compat, and apply_roles_to_package calls it to allow an
# updated Role::Tiny to use a non-updated Moo::Role
sub apply_role_to_package { shift->apply_single_role_to_package(@_) }
sub apply_roles_to_package {
my ($me, $to, @roles) = @_;
return $me->apply_role_to_package($to, $roles[0]) if @roles == 1;
my %conflicts = %{$me->_composite_info_for(@roles)->{conflicts}};
my @have = grep $to->can($_), keys %conflicts;
delete @conflicts{@have};
if (keys %conflicts) {
my $fail =
join "\n",
map {
"Due to a method name conflict between roles "
."'".join(' and ', sort values %{$conflicts{$_}})."'"
.", the method '$_' must be implemented by '${to}'"
} keys %conflicts;
die $fail;
}
# conflicting methods are supposed to be treated as required by the
# composed role. we don't have an actual composed role, but because
# we know the target class already provides them, we can instead
# pretend that the roles don't do for the duration of application.
my @role_methods = map $me->_concrete_methods_of($_), @roles;
# separate loops, since local ..., delete ... for ...; creates a scope
local @{$_}{@have} for @role_methods;
delete @{$_}{@have} for @role_methods;
# the if guard here is essential since otherwise we accidentally create
# a $INFO for something that isn't a Role::Tiny (or Moo::Role) because
# autovivification hates us and wants us to die()
if ($INFO{$to}) {
delete $INFO{$to}{methods}; # reset since we're about to add methods
}
# backcompat: allow subclasses to use apply_single_role_to_package
# to apply changes. set a local var so ours does nothing.
our %BACKCOMPAT_HACK;
if($me ne __PACKAGE__
and exists $BACKCOMPAT_HACK{$me} ? $BACKCOMPAT_HACK{$me} :
$BACKCOMPAT_HACK{$me} =
$me->can('role_application_steps')
== \&role_application_steps
&& $me->can('apply_single_role_to_package')
!= \&apply_single_role_to_package
) {
foreach my $role (@roles) {
$me->apply_single_role_to_package($to, $role);
}
}
else {
foreach my $step ($me->role_application_steps) {
foreach my $role (@roles) {
$me->$step($to, $role);
}
}
}
$APPLIED_TO{$to}{join('|',@roles)} = 1;
}
sub _composite_info_for {
my ($me, @roles) = @_;
$COMPOSITE_INFO{join('|', sort @roles)} ||= do {
foreach my $role (@roles) {
_load_module($role);
}
my %methods;
foreach my $role (@roles) {
my $this_methods = $me->_concrete_methods_of($role);
$methods{$_}{$this_methods->{$_}} = $role for keys %$this_methods;
}
my %requires;
@requires{map @{$INFO{$_}{requires}||[]}, @roles} = ();
delete $requires{$_} for keys %methods;
delete $methods{$_} for grep keys(%{$methods{$_}}) == 1, keys %methods;
+{ conflicts => \%methods, requires => [keys %requires] }
};
}
sub _composable_package_for {
my ($me, $role) = @_;
my $composed_name = 'Role::Tiny::_COMPOSABLE::'.$role;
return $composed_name if $COMPOSED{role}{$composed_name};
$me->_install_methods($composed_name, $role);
my $base_name = $composed_name.'::_BASE';
# force stash to exist so ->can doesn't complain
_getstash($base_name);
# Not using _getglob, since setting @ISA via the typeglob breaks
# inheritance on 5.10.0 if the stash has previously been accessed an
# then a method called on the class (in that order!), which
# ->_install_methods (with the help of ->_install_does) ends up doing.
{ no strict 'refs'; @{"${composed_name}::ISA"} = ( $base_name ); }
my $modifiers = $INFO{$role}{modifiers}||[];
my @mod_base;
my @modifiers = grep !$composed_name->can($_),
do { my %h; @h{map @{$_}[1..$#$_-1], @$modifiers} = (); keys %h };
foreach my $modified (@modifiers) {
push @mod_base, "sub ${modified} { shift->next::method(\@_) }";
}
my $e;
{
local $@;
eval(my $code = join "\n", "package ${base_name};", @mod_base);
$e = "Evaling failed: $@\nTrying to eval:\n${code}" if $@;
}
die $e if $e;
$me->_install_modifiers($composed_name, $role);
$COMPOSED{role}{$composed_name} = {
modifiers_only => { map { $_ => 1 } @modifiers },
};
return $composed_name;
}
sub _check_requires {
my ($me, $to, $name, $requires) = @_;
return unless my @requires = @{$requires||$INFO{$name}{requires}||[]};
if (my @requires_fail = grep !$to->can($_), @requires) {
# role -> role, add to requires, role -> class, error out
if (my $to_info = $INFO{$to}) {
push @{$to_info->{requires}||=[]}, @requires_fail;
} else {
die "Can't apply ${name} to ${to} - missing ".join(', ', @requires_fail);
}
}
}
sub _concrete_methods_of {
my ($me, $role) = @_;
my $info = $INFO{$role};
# grab role symbol table
my $stash = _getstash($role);
# reverse so our keys become the values (captured coderefs) in case
# they got copied or re-used since
my $not_methods = { reverse %{$info->{not_methods}||{}} };
$info->{methods} ||= +{
# grab all code entries that aren't in the not_methods list
map {
my $code = *{$stash->{$_}}{CODE};
( ! $code or exists $not_methods->{$code} ) ? () : ($_ => $code)
} grep !ref($stash->{$_}), keys %$stash
};
}
sub methods_provided_by {
my ($me, $role) = @_;
die "${role} is not a Role::Tiny" unless $me->is_role($role);
(keys %{$me->_concrete_methods_of($role)}, @{$INFO{$role}->{requires}||[]});
}
sub _install_methods {
my ($me, $to, $role) = @_;
my $info = $INFO{$role};
my $methods = $me->_concrete_methods_of($role);
# grab target symbol table
my $stash = _getstash($to);
# determine already extant methods of target
my %has_methods;
@has_methods{grep
+(ref($stash->{$_}) || *{$stash->{$_}}{CODE}),
keys %$stash
} = ();
foreach my $i (grep !exists $has_methods{$_}, keys %$methods) {
no warnings 'once';
my $glob = _getglob "${to}::${i}";
*$glob = $methods->{$i};
# overloads using method names have the method stored in the scalar slot
# and &overload::nil in the code slot.
next
unless $i =~ /^\(/
&& ((defined &overload::nil && $methods->{$i} == \&overload::nil)
|| (defined &overload::_nil && $methods->{$i} == \&overload::_nil));
my $overload = ${ *{_getglob "${role}::${i}"}{SCALAR} };
next
unless defined $overload;
*$glob = \$overload;
}
$me->_install_does($to);
}
sub _install_modifiers {
my ($me, $to, $name) = @_;
return unless my $modifiers = $INFO{$name}{modifiers};
if (my $info = $INFO{$to}) {
push @{$info->{modifiers}}, @{$modifiers||[]};
} else {
foreach my $modifier (@{$modifiers||[]}) {
$me->_install_single_modifier($to, @$modifier);
}
}
}
my $vcheck_error;
sub _install_single_modifier {
my ($me, @args) = @_;
defined($vcheck_error) or $vcheck_error = do {
local $@;
eval { Class::Method::Modifiers->VERSION(1.05); 1 }
? 0
: $@
};
$vcheck_error and die $vcheck_error;
Class::Method::Modifiers::install_modifier(@args);
}
my $FALLBACK = sub { 0 };
sub _install_does {
my ($me, $to) = @_;
# only add does() method to classes
return if $me->is_role($to);
my $does = $me->can('does_role');
# add does() only if they don't have one
*{_getglob "${to}::does"} = $does unless $to->can('does');
return
if $to->can('DOES') and $to->can('DOES') != (UNIVERSAL->can('DOES') || 0);
my $existing = $to->can('DOES') || $to->can('isa') || $FALLBACK;
my $new_sub = sub {
my ($proto, $role) = @_;
$proto->$does($role) or $proto->$existing($role);
};
no warnings 'redefine';
return *{_getglob "${to}::DOES"} = $new_sub;
}
sub does_role {
my ($proto, $role) = @_;
require(_MRO_MODULE);
foreach my $class (@{mro::get_linear_isa(ref($proto)||$proto)}) {
return 1 if exists $APPLIED_TO{$class}{$role};
}
return 0;
}
sub is_role {
my ($me, $role) = @_;
return !!($INFO{$role} && $INFO{$role}{is_role});
}
1;
__END__
=encoding utf-8
=head1 NAME
Role::Tiny - Roles. Like a nouvelle cuisine portion size slice of Moose.
=head1 SYNOPSIS
package Some::Role;
use Role::Tiny;
sub foo { ... }
sub bar { ... }
around baz => sub { ... }
1;
else where
package Some::Class;
use Role::Tiny::With;
# bar gets imported, but not foo
with 'Some::Role';
sub foo { ... }
# baz is wrapped in the around modifier by Class::Method::Modifiers
sub baz { ... }
1;
If you wanted attributes as well, look at L<Moo::Role>.
=head1 DESCRIPTION
C<Role::Tiny> is a minimalist role composition tool.
=head1 ROLE COMPOSITION
Role composition can be thought of as much more clever and meaningful multiple
inheritance. The basics of this implementation of roles is:
=over 2
=item *
If a method is already defined on a class, that method will not be composed in
from the role.
=item *
If a method that the role L</requires> to be implemented is not implemented,
role application will fail loudly.
=back
Unlike L<Class::C3>, where the B<last> class inherited from "wins," role
composition is the other way around, where the class wins. If multiple roles
are applied in a single call (single with statement), then if any of their
provided methods clash, an exception is raised unless the class provides
a method since this conflict indicates a potential problem.
=head1 IMPORTED SUBROUTINES
=head2 requires
requires qw(foo bar);
Declares a list of methods that must be defined to compose role.
=head2 with
with 'Some::Role1';
with 'Some::Role1', 'Some::Role2';
Composes another role into the current role (or class via L<Role::Tiny::With>).
If you have conflicts and want to resolve them in favour of Some::Role1 you
can instead write:
with 'Some::Role1';
with 'Some::Role2';
If you have conflicts and want to resolve different conflicts in favour of
different roles, please refactor your codebase.
=head2 before
before foo => sub { ... };
See L<< Class::Method::Modifiers/before method(s) => sub { ... } >> for full
documentation.
Note that since you are not required to use method modifiers,
L<Class::Method::Modifiers> is lazily loaded and we do not declare it as
a dependency. If your L<Role::Tiny> role uses modifiers you must depend on
both L<Class::Method::Modifiers> and L<Role::Tiny>.
=head2 around
around foo => sub { ... };
See L<< Class::Method::Modifiers/around method(s) => sub { ... } >> for full
documentation.
Note that since you are not required to use method modifiers,
L<Class::Method::Modifiers> is lazily loaded and we do not declare it as
a dependency. If your L<Role::Tiny> role uses modifiers you must depend on
both L<Class::Method::Modifiers> and L<Role::Tiny>.
=head2 after
after foo => sub { ... };
See L<< Class::Method::Modifiers/after method(s) => sub { ... } >> for full
documentation.
Note that since you are not required to use method modifiers,
L<Class::Method::Modifiers> is lazily loaded and we do not declare it as
a dependency. If your L<Role::Tiny> role uses modifiers you must depend on
both L<Class::Method::Modifiers> and L<Role::Tiny>.
=head2 Strict and Warnings
In addition to importing subroutines, using C<Role::Tiny> applies L<strict> and
L<warnings> to the caller.
=head1 SUBROUTINES
=head2 does_role
if (Role::Tiny::does_role($foo, 'Some::Role')) {
...
}
Returns true if class has been composed with role.
This subroutine is also installed as ->does on any class a Role::Tiny is
composed into unless that class already has an ->does method, so
if ($foo->does('Some::Role')) {
...
}
will work for classes but to test a role, one must use ::does_role directly.
Additionally, Role::Tiny will override the standard Perl C<DOES> method
for your class. However, if C<any> class in your class' inheritance
hierarchy provides C<DOES>, then Role::Tiny will not override it.
=head1 METHODS
=head2 apply_roles_to_package
Role::Tiny->apply_roles_to_package(
'Some::Package', 'Some::Role', 'Some::Other::Role'
);
Composes role with package. See also L<Role::Tiny::With>.
=head2 apply_roles_to_object
Role::Tiny->apply_roles_to_object($foo, qw(Some::Role1 Some::Role2));
Composes roles in order into object directly. Object is reblessed into the
resulting class.
=head2 create_class_with_roles
Role::Tiny->create_class_with_roles('Some::Base', qw(Some::Role1 Some::Role2));
Creates a new class based on base, with the roles composed into it in order.
New class is returned.
=head2 is_role
Role::Tiny->is_role('Some::Role1')
Returns true if the given package is a role.
=head1 CAVEATS
=over 4
=item * On perl 5.8.8 and earlier, applying a role to an object won't apply any
overloads from the role to all copies of the object.
=back
=head1 SEE ALSO
L<Role::Tiny> is the attribute-less subset of L<Moo::Role>; L<Moo::Role> is
a meta-protocol-less subset of the king of role systems, L<Moose::Role>.
Ovid's L<Role::Basic> provides roles with a similar scope, but without method
modifiers, and having some extra usage restrictions.
=head1 AUTHOR
mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
=head1 CONTRIBUTORS
dg - David Leadbeater (cpan:DGL) <dgl@dgl.cx>
frew - Arthur Axel "fREW" Schmidt (cpan:FREW) <frioux@gmail.com>
hobbs - Andrew Rodland (cpan:ARODLAND) <arodland@cpan.org>
jnap - John Napiorkowski (cpan:JJNAPIORK) <jjn1056@yahoo.com>
ribasushi - Peter Rabbitson (cpan:RIBASUSHI) <ribasushi@cpan.org>
chip - Chip Salzenberg (cpan:CHIPS) <chip@pobox.com>
ajgb - Alex J. G. Burzyński (cpan:AJGB) <ajgb@cpan.org>
doy - Jesse Luehrs (cpan:DOY) <doy at tozt dot net>
perigrin - Chris Prather (cpan:PERIGRIN) <chris@prather.org>
Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@googlemail.com>
ilmari - Dagfinn Ilmari Mannsåker (cpan:ILMARI) <ilmari@ilmari.org>
tobyink - Toby Inkster (cpan:TOBYINK) <tobyink@cpan.org>
haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org>
=head1 COPYRIGHT
Copyright (c) 2010-2012 the Role::Tiny L</AUTHOR> and L</CONTRIBUTORS>
as listed above.
=head1 LICENSE
This library is free software and may be distributed under the same terms
as perl itself.
=cut