package Dancer2::Plugin;
# ABSTRACT: base class for Dancer2 plugins
$Dancer2::Plugin::VERSION = '0.201000';
use strict;
use warnings;
use Moo;
use Carp;
use List::Util qw/ reduce /;
use Module::Runtime 'require_module';
use Attribute::Handlers;
use Scalar::Util;
our $CUR_PLUGIN;
extends 'Exporter::Tiny';
with 'Dancer2::Core::Role::Hookable';
has app => (
is => 'ro',
required => 1,
);
has config => (
is => 'ro',
lazy => 1,
default => sub {
my $self = shift;
my $config = $self->app->config;
my $package = ref $self; # TODO
$package =~ s/Dancer2::Plugin:://;
$config->{plugins}{$package} || {};
},
);
my $_keywords = {};
sub keywords { $_keywords }
my $REF_ADDR_REGEX = qr{
[A-Za-z0-9\:\_]+
=HASH
\(
([0-9a-fx]+)
\)
}x;
my %instances;
# backwards compatibility
our $_keywords_by_plugin = {};
has '+hooks' => (
default => sub {
my $plugin = shift;
my $name = 'plugin.' . lc ref $plugin;
$name =~ s/Dancer2::Plugin:://i;
$name =~ s/::/_/g;
+{
map { join( '.', $name, $_ ) => [] }
@{ $plugin->ClassHooks }
};
},
);
sub add_hooks {
my $class = shift;
push @{ $class->ClassHooks }, @_;
}
sub execute_plugin_hook {
my ( $self, $name, @args ) = @_;
my $plugin_class = ref $self;
$self->isa('Dancer2::Plugin')
or croak "Cannot call plugin hook ($name) from outside plugin";
$plugin_class =~ s/^Dancer2::Plugin:://; # short names
my $full_name = 'plugin.' . lc($plugin_class) . ".$name";
$full_name =~ s/::/_/g;
$self->app->execute_hook( $full_name, @args );
}
# both functions are there for D2::Core::Role::Hookable
# back-compatibility. Aren't used
sub supported_hooks { [] }
sub hook_aliases { $_[0]->{'hook_aliases'} ||= {} }
### has() STUFF ########################################
# our wrapping around Moo::has, done to be able to intercept
# both 'from_config' and 'plugin_keyword'
sub _p2_has {
my $class = shift;
$class->_p2_has_from_config( $class->_p2_has_keyword( @_ ) );
};
sub _p2_has_from_config {
my( $class, $name, %args ) = @_;
my $config_name = delete $args{'from_config'}
or return ( $name, %args );
$args{lazy} = 1;
if ( ref $config_name eq 'CODE' ) {
$args{default} ||= $config_name;
$config_name = 1;
}
$config_name = $name if $config_name eq '1';
my $orig_default = $args{default} || sub{};
$args{default} = sub {
my $plugin = shift;
my $value = reduce { eval { $a->{$b} } } $plugin->config, split '\.', $config_name;
return defined $value ? $value: $orig_default->($plugin);
};
return $name => %args;
}
sub _p2_has_keyword {
my( $class, $name, %args ) = @_;
if( my $keyword = delete $args{plugin_keyword} ) {
$keyword = $name if $keyword eq '1';
$class->keywords->{$_} = sub { (shift)->$name(@_) }
for ref $keyword ? @$keyword : $keyword;
}
return $name => %args;
}
### ATTRIBUTE HANDLER STUFF ########################################
# :PluginKeyword shenanigans
sub PluginKeyword :ATTR(CODE) {
my( $class, $sym_ref, $code, undef, $args ) = @_;
my $func_name = *{$sym_ref}{NAME};
$args = join '', @$args if ref $args eq 'ARRAY';
for my $name ( split ' ', $args || $func_name ) {
$class->keywords->{$name} = $code;
}
}
## EXPORT STUFF ##############################################################
# this @EXPORT will only be taken
# into account when we do a 'use Dancer2::Plugin'
# I.e., it'll only do its magic for the
# plugins themselves, not when they are
# called
our @EXPORT = qw/ :plugin /;
# compatibility - it will be removed soon!
my $no_dsl = {};
my $exported_app = {};
sub _exporter_expand_tag {
my( $class, $name, $args, $global ) = @_;
my $caller = $global->{into};
$name eq 'no_dsl' and $no_dsl->{$caller} = 1;
# no_dsl check here is for compatibility only
# it will be removed soon!
return _exporter_plugin($caller)
if $name eq 'plugin' or $name eq 'no_dsl';
return _exporter_app($class,$caller,$global)
if $name eq 'app' and $caller->can('app') and !$no_dsl->{$class};
return;
}
# plugin has been called within a D2 app. Modify
# the app and export keywords
sub _exporter_app {
my( $class, $caller, $global ) = @_;
$exported_app->{$caller} = 1;
my $app = eval "${caller}::app()" or return; ## no critic
return unless $app->can('with_plugin');
my $plugin = $app->with_plugin( "+" . $class );
$global->{plugin} = $plugin;
return unless $class->can('keywords');
# Add our hooks to the app, so they're recognized
# this is for compatibility so you can call execute_hook()
# without the fully qualified plugin name.
# The reason we need to do this here instead of when adding a
# hook is because we need to register in the app, and only now it
# exists.
# This adds a caveat that two plugins cannot register
# the same hook name, but that will be deprecated anyway.
{;
foreach my $hook ( @{ $plugin->ClassHooks } ) {
my $full_name = 'plugin.' . lc($class) . ".$hook";
$full_name =~ s/Dancer2::Plugin:://i;
$full_name =~ s/::/_/g;
# this adds it to the plugin
$plugin->hook_aliases->{$hook} = $full_name;
# this adds it to the app
$plugin->app->hook_aliases->{$hook} = $full_name;
# copy the hooks from the plugin to the app
# this is in case they were created at import time
# rather than after
@{ $plugin->app->hooks }{ keys %{ $plugin->hooks } } =
values %{ $plugin->hooks };
}
}
{
# get the reference
my ($plugin_addr) = "$plugin" =~ $REF_ADDR_REGEX;
$instances{$plugin_addr}{'config'} = sub { $plugin->config };
$instances{$plugin_addr}{'app'} = $plugin->app;
Scalar::Util::weaken( $instances{$plugin_addr}{'app'} );
## no critic
no strict 'refs';
# we used a forward declaration
# so the compiled form "plugin_setting;" can be overridden
# with this implementation,
# which works on runtime ("plugin_setting()")
# we can't use can() here because the forward declaration will
# create a CODE stub
no warnings 'redefine';
*{"${class}::plugin_setting"} = sub {
my ($plugin_addr) = "$CUR_PLUGIN" =~ $REF_ADDR_REGEX;
$plugin_addr
or Carp::croak('Can\'t find originating plugin');
# we need to do this because plugins might call "set"
# in order to change plugin configuration but it doesn't
# change the plugin object, it changes the app object
# so we merge them.
my $name = ref $CUR_PLUGIN;
$name =~ s/^Dancer2::Plugin:://g;
my $plugin_inst = $instances{$plugin_addr};
my $plugin_config = $plugin_inst->{'config'}->();
my $app_plugin_config = $plugin_inst->{'app'}->config->{'plugins'}{$name};
return { %{ $plugin_config || {} }, %{ $app_plugin_config || {} } };
};
# FIXME:
# why doesn't this work? it's like it's already defined somewhere
# but i'm not sure where. seems like AUTOLOAD runs it.
#$class->can('execute_hook') or
*{"${class}::execute_hook"} = sub {
# this can also be called by App.pm itself
# if the plugin is a
# "candidate" for a hook
# See: App.pm "execute_hook" method, "around" modifier
if ( $_[0]->isa('Dancer2::Plugin') ) {
# this means it's probably our hook, we need to verify it
my ( $plugin_self, $hook_name, @args ) = @_;
my $plugin_class = lc $class;
$plugin_class =~ s/^dancer2::plugin:://;
$plugin_class =~ s{::}{_}g;
# you're either calling it with the full qualifier or not
# if not, use the execute_plugin_hook instead
if ( $plugin->hooks->{"plugin.$plugin_class.$hook_name"} ) {
Carp::carp("Please use fully qualified hook name or "
. "the method execute_plugin_hook");
$hook_name = "plugin.$plugin_class.$hook_name";
}
$hook_name =~ /^plugin\.$plugin_class/
or Carp::croak('Unknown plugin called through other plugin');
# now we can't really use the app to execute it because
# the "around" modifier is the one calling us to begin
# with, so we need to call it directly ourselves
# this is okay because the modifier is there only to
# call candidates, like us (this is in fact how and
# why we were called)
$_->( $plugin_self, @args )
for @{ $plugin->hooks->{$hook_name} };
return;
}
return $plugin->app->execute_hook(@_);
};
}
local $CUR_PLUGIN = $plugin;
$_->($plugin) for @{ $plugin->_DANCER2_IMPORT_TIME_SUBS() };
map { [ $_ => {plugin => $plugin} ] } keys %{ $plugin->keywords };
}
# turns the caller namespace into
# a D2P2 class, with exported keywords
sub _exporter_plugin {
my $caller = shift;
require_module('Dancer2::Core::DSL');
my $keywords_list = join ' ', keys %{ Dancer2::Core::DSL->dsl_keywords };
eval <<"END"; ## no critic
{
package $caller;
use Moo;
use Carp ();
use Attribute::Handlers;
extends 'Dancer2::Plugin';
our \@EXPORT = ( ':app' );
around has => sub {
my( \$orig, \@args ) = \@_;
\$orig->( ${caller}->_p2_has( \@args) );
};
sub PluginKeyword :ATTR(CODE) {
goto &Dancer2::Plugin::PluginKeyword;
}
sub execute_plugin_hook {
goto &Dancer2::Plugin::execute_plugin_hook;
}
my \$_keywords = {};
sub keywords { \$_keywords }
my \$_ClassHooks = [];
sub ClassHooks { \$_ClassHooks }
# this is important as it'll do the keywords mapping between the
# plugin and the app
sub register_plugin { Dancer2::Plugin::register_plugin(@_) }
sub register {
my ( \$keyword, \$sub ) = \@_;
\$_keywords->{\$keyword} = \$sub;
\$keyword =~ /^[a-zA-Z_]+[a-zA-Z0-9_]*\$/
or Carp::croak(
"You can't use '\$keyword', it is an invalid name"
. " (it should match ^[a-zA-Z_]+[a-zA-Z0-9_]*\\\$ )");
grep +( \$keyword eq \$_ ), qw<$keywords_list>
and Carp::croak("You can't use '\$keyword', this is a reserved keyword");
\$Dancer2::Plugin::_keywords_by_plugin->{\$keyword}
and Carp::croak("You can't use \$keyword, "
. "this is a keyword reserved by "
. \$Dancer2::Plugin::_keywords_by_plugin->{\$keyword});
\$Dancer2::Plugin::_keywords_by_plugin->{\$keyword} = "$caller";
# Exporter::Tiny doesn't seem to generate the subs
# in the caller properly, so we have to do it manually
{
no strict 'refs';
*{"${caller}::\$keyword"} = \$sub;
}
}
my \@_DANCER2_IMPORT_TIME_SUBS;
sub _DANCER2_IMPORT_TIME_SUBS {\\\@_DANCER2_IMPORT_TIME_SUBS}
sub on_plugin_import (&) {
push \@_DANCER2_IMPORT_TIME_SUBS, \$_[0];
}
sub register_hook { goto &plugin_hooks }
sub plugin_setting {};
sub plugin_args {
Carp::carp "Plugin DSL method 'plugin_args' is deprecated. "
. "Use '\\\@_' instead'.\n";
\@_;
}
}
END
$no_dsl->{$caller} or eval <<"END"; ## no critic
{
package $caller;
# FIXME: AUTOLOAD might pick up on this
sub dancer_app {
Carp::carp "Plugin DSL method 'dancer_app' is deprecated. "
. "Use '\\\$self->app' instead'.\n";
\$_[0]->app;
}
# FIXME: AUTOLOAD might pick up on this
sub request {
Carp::carp "Plugin DSL method 'request' is deprecated. "
. "Use '\\\$self->app->request' instead'.\n";
\$_[0]->app->request;
}
# FIXME: AUTOLOAD might pick up on this
sub var {
Carp::carp "Plugin DSL method 'var' is deprecated. "
. "Use '\\\$self->app->request->var' instead'.\n";
shift->app->request->var(\@_);
}
# FIXME: AUTOLOAD might pick up on this
sub hook {
Carp::carp "Plugin DSL method 'hook' is deprecated. "
. "Use '\\\$self->app->add_hook' instead'.\n";
shift->app->add_hook(
Dancer2::Core::Hook->new( name => shift, code => shift ) );
}
}
END
die $@ if $@;
return map { [ $_ => { class => $caller } ] }
qw/ plugin_keywords plugin_hooks /;
}
# This has to be called for now at the end of every plugin package, in order to
# map the keywords of the associated app to the plugin, so that these keywords
# can be called from within the plugin code. This function is deprecated, as
# it's tied to the old plugin system. It's kept here for backcompat reason, but
# should go away with the old plugin system.
sub register_plugin {
my $plugin_module = caller(1);
# if you ask yourself why we do the injection in the plugin
# module namespace every time the plugin is used, and not only
# once, it's because it can be used by different app that could
# have a different DSL with a different list of keywords.
my $_DANCER2_IMPORT_TIME_SUBS = $plugin_module->_DANCER2_IMPORT_TIME_SUBS;
unshift(@$_DANCER2_IMPORT_TIME_SUBS, sub {
my $app_dsl_cb;
## no critic qw(ControlStructures::ProhibitCStyleForLoops)
for ( my $i = 0; my $caller = caller($i); $i++ ) {
$app_dsl_cb = $caller->can('dsl')
and last;
}
$app_dsl_cb
or croak('Could not find Dancer2 app');
foreach my $keyword ( keys %{ $app_dsl_cb->()->dsl_keywords} ) {
# if not yet defined, inject the keyword in the plugin
# namespace, but make sure the code will always get the
# coderef from the right associated app, because one plugin
# can be used by multiple apps. Note that we remove the
# first parameter (plugin instance) from what we pass to
# the keyword implementation of the App
no strict 'refs';
$plugin_module->can($keyword)
or *{"${plugin_module}::$keyword"} = sub {
my $coderef = shift()->app->name->can($keyword);
$coderef->(@_);
};
}
});
}
sub _exporter_expand_sub {
my( $plugin, $name, $args, $global ) = @_;
my $class = $args->{class};
return _exported_plugin_keywords($plugin,$class)
if $name eq 'plugin_keywords';
return _exported_plugin_hooks($class)
if $name eq 'plugin_hooks';
$exported_app->{ $global->{'into'} }
or Carp::croak('Specific subroutines cannot be exported from plugin');
# otherwise, we're exporting a keyword
my $p = $args->{plugin};
my $sub = $p->keywords->{$name};
return $name => sub(@) {
# localize the plugin so we can get it later
local $CUR_PLUGIN = $p;
$sub->($p,@_);
}
}
# "There's a good reason for this, I swear!"
# -- Sawyer X
# basically, if someone adds a hook to the app directly
# that needs to access a DSL that needs the current object
# (such as "plugin_setting"),
# that object needs to be available
# So:
# we override App's "add_hook" to provide a register a
# different hook callback, that closes over the plugin when
# it's available, relocalizes it when the callback runs and
# after localizing it, calls the original hook callback
{
## no critic;
no strict 'refs';
no warnings 'redefine';
my $orig_cb = Dancer2::Core::App->can('add_hook');
$orig_cb and *{'Dancer2::Core::App::add_hook'} = sub {
my ( $app, $hook ) = @_;
my $hook_code = $hook->code;
my $plugin = $CUR_PLUGIN;
$hook->{'code'} = sub {
local $CUR_PLUGIN = $plugin;
$hook_code->(@_);
};
$orig_cb->(@_);
};
}
# define the exported 'plugin_keywords'
sub _exported_plugin_keywords{
my( $plugin, $class ) = @_;
return plugin_keywords => sub(@) {
while( my $name = shift @_ ) {
## no critic
my $sub = ref $_[0] eq 'CODE'
? shift @_
: eval '\&'.$class."::" . ( ref $name ? $name->[0] : $name );
$class->keywords->{$_} = $sub for ref $name ? @$name : $name;
}
}
}
sub _exported_plugin_hooks {
my $class = shift;
return plugin_hooks => sub (@) { $class->add_hooks(@_) }
}
1;
__END__
=pod
=encoding UTF-8
=head1 NAME
Dancer2::Plugin - base class for Dancer2 plugins
=head1 VERSION
version 0.201000
=head1 SYNOPSIS
The plugin itself:
package Dancer2::Plugin::Polite;
use strict;
use warnings;
use Dancer2::Plugin;
has smiley => (
is => 'ro',
default => sub {
$_[0]->config->{smiley} || ':-)'
}
);
plugin_keywords 'add_smileys';
sub BUILD {
my $plugin = shift;
$plugin->app->add_hook( Dancer2::Core::Hook->new(
name => 'after',
code => sub { $_[0]->content( $_[0]->content . " ... please?" ) }
));
$plugin->app->add_route(
method => 'get',
regexp => '/goodbye',
code => sub {
my $app = shift;
'farewell, ' . $app->request->params->{name};
},
);
}
sub add_smileys {
my( $plugin, $text ) = @_;
$text =~ s/ (?<= \. ) / $plugin->smiley /xeg;
return $text;
}
1;
then to load into the app:
package MyApp;
use strict;
use warnings;
use Dancer2;
BEGIN { # would usually be in config.yml
set plugins => {
Polite => {
smiley => '8-D',
},
};
}
use Dancer2::Plugin::Polite;
get '/' => sub {
add_smileys( 'make me a sandwich.' );
};
1;
=head1 DESCRIPTION
This is an alternate plugin basis for Dancer2.
=head2 Writing the plugin
=head3 C<use Dancer2::Plugin>
The plugin must begin with
use Dancer2::Plugin;
which will turn the package into a L<Moo> class that inherits from L<Dancer2::Plugin>. The base class provides the plugin with
two attributes: C<app>, which is populated with the Dancer2 app object for which
the plugin is being initialized for, and C<config> which holds the plugin
section of the application configuration.
=head3 Modifying the app at building time
If the plugin needs to tinker with the application -- add routes or hooks, for example --
it can do so within its C<BUILD()> function.
sub BUILD {
my $plugin = shift;
$plugin->app->add_route( ... );
}
=head3 Adding keywords
=head4 Via C<plugin_keywords>
Keywords that the plugin wishes to export to the Dancer2 app can be defined via the C<plugin_keywords> keyword:
plugin_keywords qw/
add_smileys
add_sad_kitten
/;
Each of the keyword will resolve to the class method of the same name. When invoked as keyword, it'll be passed
the plugin object as its first argument.
sub add_smileys {
my( $plugin, $text ) = @_;
return join ' ', $text, $plugin->smiley;
}
# and then in the app
get '/' => sub {
add_smileys( "Hi there!" );
};
You can also pass the functions directly to C<plugin_keywords>.
plugin_keywords
add_smileys => sub {
my( $plugin, $text ) = @_;
$text =~ s/ (?<= \. ) / $plugin->smiley /xeg;
return $text;
},
add_sad_kitten => sub { ... };
Or a mix of both styles. We're easy that way:
plugin_keywords
add_smileys => sub {
my( $plugin, $text ) = @_;
$text =~ s/ (?<= \. ) / $plugin->smiley /xeg;
return $text;
},
'add_sad_kitten';
sub add_sad_kitten {
...;
}
If you want several keywords to be synonyms calling the same
function, you can list them in an arrayref. The first
function of the list is taken to be the "real" method to
link to the keywords.
plugin_keywords [qw/ add_smileys add_happy_face /];
sub add_smileys { ... }
Calls to C<plugin_keywords> are cumulative.
=head4 Via the C<:PluginKeyword> function attribute
Keywords can also be defined by adding the C<:PluginKeyword> attribute
to the function you wish to export.
sub foo :PluginKeyword { ... }
sub bar :PluginKeyword( baz quux ) { ... }
# equivalent to
sub foo { ... }
sub bar { ... }
plugin_keywords 'foo', [ qw/ baz quux / ] => \&bar;
=head4 For an attribute
You can also turn an attribute of the plugin into a keyword.
has foo => (
is => 'ro',
plugin_keyword => 1, # keyword will be 'foo'
);
has bar => (
is => 'ro',
plugin_keyword => 'quux', # keyword will be 'quux'
);
has baz => (
is => 'ro',
plugin_keyword => [ 'baz', 'bazz' ], # keywords will be 'baz' and 'bazz'
);
=head3 Accessing the plugin configuration
The plugin configuration is available via the C<config()> method.
sub BUILD {
my $plugin = shift;
if ( $plugin->config->{feeling_polite} ) {
$plugin->app->add_hook( Dancer2::Core::Hook->new(
name => 'after',
code => sub { $_[0]->content( $_[0]->content . " ... please?" ) }
));
}
}
=head3 Getting default values from config file
Since initializing a plugin with either a default or a value passed via the configuration file,
like
has smiley => (
is => 'ro',
default => sub {
$_[0]->config->{smiley} || ':-)'
}
);
C<Dancer2::Plugin> allows for a C<from_config> key in the attribute definition.
Its value is the plugin configuration key that will be used to initialize the attribute.
If it's given the value C<1>, the name of the attribute will be taken as the configuration key.
Nested hash keys can also be referred to using a dot notation.
If the plugin configuration has no value for the given key, the attribute default, if specified, will be honored.
If the key is given a coderef as value, it's considered to be a C<default> value combo:
has foo => (
is => 'ro',
from_config => sub { 'my default' },
);
# equivalent to
has foo => (
is => 'ro',
from_config => 'foo',
default => sub { 'my default' },
);
For example:
# in config.yml
plugins:
Polite:
smiley: ':-)'
greeting:
casual: Hi!
formal: How do you do?
# in the plugin
has smiley => ( # will be ':-)'
is => 'ro',
from_config => 1,
default => sub { ':-(' },
);
has casual_greeting => ( # will be 'Hi!'
is => 'ro',
from_config => 'greeting.casual',
);
has apology => ( # will be 'sorry'
is => 'ro',
from_config => 'apology',
default => sub { 'sorry' },
)
has closing => ( # will be 'See ya!'
is => 'ro',
from_config => sub { 'See ya!' },
);
=head3 Accessing the parent Dancer app
If the plugin is instantiated within a Dancer app, it'll be
accessible via the method C<app()>.
sub BUILD {
my $plugin = shift;
$plugin->app->add_route( ... );
}
=head2 Using the plugin within the app
A plugin is loaded via
use Dancer2::Plugin::Polite;
The plugin will assume that it's loading within a Dancer module and will
automatically register itself against its C<app()> and export its keywords
to the local namespace. If you don't want this to happen, specify that you
don't want anything imported via empty parentheses when C<use>ing the module:
use Dancer2::Plugin::Polite ();
=head2 Plugins using plugins
This is a (relatively) simple way for a plugin to use another plugin:
package Dancer2::Plugin::SourPuss;
has polite => (
is => 'ro',
lazy => 1,
default => sub {
# if the app already has the 'Polite' plugin loaded, it'll return
# it. If not, it'll load it in the app, and then return it.
$_[0]->app->with_plugin( 'Polite' )
},
handles => { 'smiley' => 'smiley' },
);
sub keywords { qw/ killjoy / }
sub killjoy {
my( $plugin, $text ) = @_;
my $smiley = $plugin->smiley;
$text =~ s/ $smiley />:-(/xg;
$text;
}
=head2 Hooks
New plugin hooks are declared via C<plugin_hooks>.
plugin_hooks 'my_hook', 'my_other_hook';
Hooks are prefixed with C<plugin.plugin_name>. So the plugin
C<my_hook> coming from the plugin C<Dancer2::Plugin::MyPlugin> will have the hook name
C<plugin.myplugin.my_hook>.
Hooks are executed within the plugin by calling them via the associated I<app>.
$plugin->execute_plugin_hook( 'my_hook' );
You can also call any other hook if you provide the full name using the
C<execute_hook> method:
$plugin->app->execute_hook( 'core.app.route_exception' );
Or using their alias:
$plugin->app->execute_hook( 'on_route_exception' );
=head2 Writing Test Gotchas
=head3 Constructor for Dancer2::Plugin::Foo has been inlined and cannot be updated
You'll usually get this one because you are defining both the plugin and app
in your test file, and the runtime creation of Moo's attributes happens after
the compile-time import voodoo dance.
To get around this nightmare, wrap your plugin definition in a C<BEGIN> block.
BEGIN {
package Dancer2::Plugin::Foo;
use Dancer2::Plugin;
has bar => (
is => 'ro',
from_config => 1,
);
plugin_keywords qw/ bar /;
}
{
package MyApp;
use Dancer2;
use Dancer2::Plugin::Foo;
bar();
}
=head3 You cannot overwrite a locally defined method (bar) with a reader
If you set an object attribute of your plugin to be a keyword as well, you need
to call C<plugin_keywords> after the attribute definition.
package Dancer2::Plugin::Foo;
use Dancer2::Plugin;
has bar => (
is => 'ro',
);
plugin_keywords 'bar';
=head1 AUTHOR
Dancer Core Developers
=head1 COPYRIGHT AND LICENSE
This software is copyright (c) 2016 by Alexis Sukrieh.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
=cut