source: perl/modules/Facebook/lib/Ouch.pm @ 0792d99

use strict;
use warnings;
package Ouch;
BEGIN {
  $Ouch::VERSION = '0.0401';
}
use Carp qw(longmess shortmess);
use parent 'Exporter';
use overload bool => sub {1}, q{""} => 'scalar', fallback => 1;

our @EXPORT = qw(bleep ouch kiss hug barf);
our @EXPORT_OK = qw(try throw catch catch_all caught caught_all);
our %EXPORT_TAGS = ( traditional => [qw(try throw catch catch_all)], trytiny => [qw( throw caught caught_all )] );

sub new {
  my ($class, $code, $message, $data) = @_;
  bless {code => $code, message => $message, data => $data, shortmess => shortmess($message), trace => longmess($message) }, $class;
}

sub try (&) {
  my $try = shift;
  eval { $try->() };
  return $@;
}

sub ouch {
  my ($code, $message, $data) = @_;
  my $self = __PACKAGE__->new($code, $message, $data);
  die $self;
}

sub throw {  # alias
  ouch @_;
}

sub kiss {
  my ($code, $e) = @_;
  $e ||= $@;
  if (ref $e eq 'Ouch' && $e->code eq $code) {
    return 1;
  }
  return 0;
}

sub catch {
  kiss @_;
}

sub caught {
  kiss @_;
}

sub hug {
  my ($e) = @_;
  $e ||= $@;
  return $@ ? 1 : 0;
}

sub catch_all {
  hug @_;
}

sub caught_all {
  hug @_;
}

sub bleep {
  my ($e) = @_;
  $e ||= $@;
  if (ref $e eq 'Ouch') {
    return $e->message;
  }
  else {
    my $message = $@;
    if ($message =~ m{^(.*)\s+at\s.*line\s\d+.}xms) {
        return $1;
    }
    else {
        return $message;
    }
  }
}

sub barf {
    my ($e) = @_;
    my $code;
    $e ||= $@;
    if (ref $e eq 'Ouch') {
        $code = $e->code;
    } 
    else {
        $code = 1;
    }

    print STDERR bleep($e)."\n";
    exit $code;
}

sub scalar {
  my $self = shift;
  return $self->{shortmess};
}

sub trace {
  my $self = shift;
  return $self->{trace};
}

sub hashref {
  my $self = shift;
  return {
    code    => $self->{code},
    message => $self->{message},
    data    => $self->{data},
  };
}

sub code {
  my $self = shift;
  return $self->{code};
}

sub message {
  my $self = shift;
  return $self->{message};
}

sub data {
  my $self = shift;
  return $self->{data};
}

=head1 NAME

Ouch - Exceptions that don't hurt.

=head1 VERSION

version 0.0401

=head1 SYNOPSIS

 use Ouch;

 eval { ouch(404, 'File not found.'); };

 if (kiss 404) {
   check_elsewhere();
 }

 say $@;           # These two lines do the
 say $@->scalar;   # same thing.

=head1 DESCRIPTION

Ouch provides a class for exception handling that doesn't require a lot of boilerplate, nor any up front definition. If L<Exception::Class>
is working for you, great! But if you want something that is faster, easier to use, requires less typing, and has no prereqs, but still gives 
you much of that same functionality, then Ouch is for you.

=head2 Why another exception handling module?

It really comes down to L<Carp> isn't enough for me, and L<Exception::Class> does what I want but makes me type way too much. Also, I tend to work on a lot of protocol-based systems that use error codes (HTTP, FTP, SMTP, JSON-RPC) rather than error classes, so that feels more natural to me. Consider the difference between these:

B<Ouch>

 use Ouch;
 ouch 404, 'File not found.', 'file';

B<Exception::Class>

 use Exception::Class (
    'FileNotFound' => {
        fields  => [ 'code', 'field' ],
    },
 );
 FileNotFound->throw( error => 'File not found.', code => 404, field => 'file' );

And if you want to catch the exception you're looking at:

B<Ouch>

 if (kiss 404) {
   # do something
 }

B<Exception::Class>

 my $e;
 if ($e = Exception::Class->caught('FileNotFound')) {
   # do something
 }

Those differences may not seem like a lot, but over any substantial program with lots of exceptions it can become a big deal. 

=head2 Usage

Most of the time, all you need to do is:

 ouch $code, $message, $data;
 ouch -32700, 'Parse error.', $request; # JSON-RPC 2.0 error
 ouch 441, 'You need to specify an email address.', 'email'; # form processing error
 ouch 'missing_param', 'You need to specify an email address.', 'email';

You can also go long form if you prefer:

 die Ouch->new($code, $message, $data);

=head2 Functional Interface

=head3 ouch

Some nice sugar instead of using the object oriented interface.

 ouch 2121, 'Did not do the big thing.';

=over

=item code

An error code. An integer or string representing error type. Try to stick to codes used in whatever domain you happen to be working in. HTTP Status codes. JSON-RPC error codes, etc.

=item message

A human readable error message.

=item data

Optional. Anything you want to attach to the exception to help a developer catching it decide what to do. For example, if you're doing form processing, you might want this to be the name of the field that caused the exception. 

B<WARNING:> Do not include objects or code refs in your data. This should only be stuff that is easily serializable like scalars, array refs, and hash refs.

=back

=head3 kiss

Some nice sugar to trap an Ouch.

 if (kiss $code) {
    # make it go
 }

=over

=item code

The code you're looking for.

=item exception

Optional. If you like you can pass the exception into C<kiss>. If not, it will just use whatever is in C<$@>. You might want to do this if you've saved the exception before running another C<eval>, for example.

=back


=head3 hug

Some nice sugar to trap any exception.

 if (hug) {
   # make it stop
 }

=over 

=item exception

Optional. If you like you can pass the exception into C<hug>. If not, it will just use whatever is in C<$@>.

=back


=head3 bleep 

A little sugar to make exceptions human friendly. Returns a clean error message from any exception, including an Ouch.

 File not found.

Rather than:

 File not found. at /Some/File.pm line 63.

=over

=item exception

Optional. If you like you can pass the exception into C<bleep>. If not, it will just use whatever is in C<$@>.

=back

=head3

Calls C<bleep>, and then exits with error code

=over

=item exception

Optional. You can pass an exception into C<barf> which then gets passed to C<bleep> otherwise it will use whatever's in C<$@>

=back


=head2 Object-Oriented Interface

=head3 new

Constructor for the object-oriented interface. Takes the same parameters as C<ouch>.

 Ouch->new($code, $message, $data);

=head3 scalar

Returns the scalar form of the error message:

 Crap! at /Some/File.pm line 43.

Just as if you had done:

 die 'Crap!';

Rather than:

 ouch $code, 'Crap!'; 

=head3 trace

Call this if you want the full stack trace that lead up to the ouch.

=head3 hashref

Returns a formatted hash reference of the exception, which can be useful for handing off to a serializer like L<JSON>.

 {
   code     => $code,
   message  => $message,
   data     => $data,
 }

=head3 code

Returns the C<code> passed into the constructor.

=head3 message

Returns the C<messsage> passed into the constructor.

=head3 data

Returns the C<data> passed into the constructor.

=head2 Traditional Interface

Some people just can't bring themselves to use the sugary cuteness of Ouch. For them there is the C<:traditional> interface. Here's how it works:

 use Ouch qw(:traditional);

 my $e = try {
   throw 404, 'File not found.';
 };

 if ( catch 404, $e ) {
   # do the big thing
 }
 elsif ( catch_all $e ) {
   # make it stop
 }
 else {
   # make it go
 }

B<NOTE:> C<try> also populates C<$@>, and C<catch> and C<catch_all> will also use C<$@> if you don't specify an exception.

=head3 try

Returns an exception. Is basically just a nice wrapper around C<eval>.

=over

=item block

Try accepts a code ref, anonymous subroutine, or a block. 

B<NOTE:> You need a semi-colon at the end of a C<try> block.

=back

=head3 throw

Works exactly like C<ouch>. See C<ouch> for details.

=head3 catch

Works exactly like C<kiss>. See C<kiss> for details.

=head3 catch_all

Works exactly like C<hug>. See C<hug> for details.

=head2 Try::Tiny

Many Ouch users, like to use Ouch with L<Try::Tiny>, and some of them are sticks in the mud who can't bring themselves to C<ouch> and C<kiss>, and don't like that C<:traditional> walks all over C<try> and C<catch> For them, there is the C<:trytiny> interface. Here's how it works:

 use Try::Tiny;
 use Ouch qw(:trytiny);

 try {
    throw(404, 'File not found!';
 }
 catch {
    if (caught($_)) {
        # do something
    }
    else {
        throw($_); # rethrow
    }
 };


=head1 SUPPORT

=over

=item Repository

L<http://github.com/rizen/Ouch>

=item Bug Reports

L<http://github.com/rizen/Ouch/issues>

=back


=head1 SEE ALSO

If you're looking for something lighter, check out L<Carp> that ships with Perl. Or if you're looking for something heavier check out L<Exception::Class>.

=head1 AUTHOR

JT Smith <jt_at_plainblack_dot_com>

=head1 LEGAL

Ouch is Copyright 2011 Plain Black Corporation (L<http://www.plainblack.com>) and is licensed under the same terms as Perl itself.

=cut

1;