use v5.14;
use Test::More;

package Foo
{
	use Moose;
	has foo => (
		traits  => ['MooseX::IgnoreFalse::Trait::Attribute'],
		is      => 'ro',
		default => 'whatever',
	);
}

is(Foo->new(foo => 'xyz')->foo, 'xyz');
is(Foo->new(foo => '0')->foo,   'whatever');
is(Foo->new(foo => '')->foo,    'whatever');
is(Foo->new(foo => undef)->foo, 'whatever');

done_testing;

##</code><code>##

use v5.14;

package MooseX::IgnoreFalse::Trait::Attribute
{
	use Moose::Role;
	after _process_options => sub
	{
		my ($class, $name, $options) = @_;
		
		$options->{initializer} = sub
		{
			my ($instance, $value, $setter) = @_;
			my $meta = $instance->meta->get_attribute($name);
				
			$value             ? $setter->( $value ) :
			$meta->has_default ? $setter->( $meta->default($instance) ) :
			$meta->has_builder ? $setter->( $meta->_call_builder($instance) ) :
			                     ();
		}
	};
}

##</code><code>##

use v5.14;

package MooseX::IgnoreFalse::Trait::Attribute
{
	use Moose::Role;
	after _process_options => sub
	{
		my ($class, $name, $options) = @_;
		
		if (my $orig = $options->{initializer})
		{
			$options->{initializer} = sub
			{
				my ($instance, $value, $setter) = @_;
				my $meta = $instance->meta->get_attribute($name);
				
				$value             ? $orig->( $instance, $value, $setter ) :
				$meta->has_default ? $orig->( $instance, $meta->default($instance), $setter ) :
				$meta->has_builder ? $orig->( $instance, $meta->_call_builder($instance), $setter ) :
				                     ();
			}
		}
		else
		{
			$options->{initializer} = sub
			{
				my ($instance, $value, $setter) = @_;
				my $meta = $instance->meta->get_attribute($name);
				
				$value             ? $setter->( $value ) :
				$meta->has_default ? $setter->( $meta->default($instance) ) :
				$meta->has_builder ? $setter->( $meta->_call_builder($instance) ) :
				                     ();
			}
		}
	};
}