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lib/Config/MVP/Reader/Finder.pm  view on Meta::CPAN

package Config::MVP::Reader::Finder 2.200013;
# ABSTRACT: a reader that finds an appropriate file

use Moose;
extends 'Config::MVP::Reader';

#pod =head1 DESCRIPTION
#pod
#pod The Finder reader multiplexes many other readers that implement the
#pod L<Config::MVP::Reader::Findable> role.  It uses L<Module::Pluggable> to search
#pod for modules, limits them to objects implementing the Findable role, and then
#pod selects the those which report that they are able to read a configuration file
#pod found in the config root directory.  If exactly one findable configuration
#pod reader finds a file, it is used to read the file and the configuration sequence
#pod is returned.  Otherwise, an exception is raised.
#pod
#pod Config::MVP::Reader::Finder's C<build_assembler> method will decline a new
#pod assembler, so if none was passed to C<read_config>, the Findable reader to
#pod which reading is delegated will be responsible for building the assembler,
#pod unless a Finder subclass overrides C<build_assembler> to set a default across
#pod all possible delegates.
#pod
#pod =cut

use Config::MVP::Error;
use Module::Pluggable::Object;
use Try::Tiny;

#pod =method default_search_path
#pod
#pod This is the default search path used to find configuration readers.  This
#pod method should return a list, and by default returns:
#pod
#pod   qw( Config::MVP::Reader )
#pod
#pod =cut

sub default_search_path {
  return qw(Config::MVP::Reader)
}

our @DONT_FIND;

has _module_pluggable_object => (
  is => 'ro',
  init_arg => undef,
  default  => sub {
    my ($self) = @_;
    Module::Pluggable::Object->new(
      search_path => [ $self->default_search_path ],
      inner       => 0,
      require     => 1,

      # This facility here entirely for testing. -- rjbs, 2014-07-02
      except      => \@DONT_FIND,
    );
  },
);

sub _which_reader {
  my ($self, $location) = @_;

  my @options;

  for my $pkg ($self->_module_pluggable_object->plugins) {
    next unless $pkg->isa('Moose::Object');
    next unless $pkg->does('Config::MVP::Reader::Findable');

    my $location = $pkg->refined_location($location);

    next unless defined $location;

    push @options, [ $pkg, $location ];
  }

  Config::MVP::Error->throw("no viable configuration could be found")
    unless @options;

  # XXX: Improve this error message -- rjbs, 2010-05-24
  Config::MVP::Error->throw("multiple possible config plugins found")
    if @options > 1;

  return {
    'package'  => $options[0][0],
    'location' => $options[0][1],
  };
}