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#============================================================= -*-Perl-*-
#
# Template::Plugin::Assert
#
# DESCRIPTION
# Template Toolkit plugin module which allows you to assert that
# items fetches from the stash are defined.
#
# AUTHOR
# Andy Wardley <abw@wardley.org>
#
# COPYRIGHT
# Copyright (C) 2008-2022 Andy Wardley. All Rights Reserved.
#
# This module is free software; you can redistribute it and/or
# modify it under the same terms as Perl itself.
#
#============================================================================
package Template::Plugin::Assert;
use base 'Template::Plugin';
use strict;
use warnings;
use Template::Exception;
our $VERSION = '3.100';
our $MONAD = 'Template::Monad::Assert';
our $EXCEPTION = 'Template::Exception';
our $AUTOLOAD;
sub load {
my $class = shift;
my $context = shift;
my $stash = $context->stash;
my $vmethod = sub {
$MONAD->new($stash, shift);
};
# define .assert vmethods for hash and list objects
$context->define_vmethod( hash => assert => $vmethod );
$context->define_vmethod( list => assert => $vmethod );
return $class;
}
sub new {
my ($class, $context, @args) = @_;
# create an assert plugin object which will handle simple variable
# lookups.
return bless { _CONTEXT => $context }, $class;
}
sub AUTOLOAD {
my ($self, @args) = @_;
my $item = $AUTOLOAD;
$item =~ s/.*:://;
return if $item eq 'DESTROY';
# lookup the named values
my $stash = $self->{ _CONTEXT }->stash;
my $value = $stash->dotop($stash, $item, \@args);
if (! defined $value) {
die $EXCEPTION->new( assert => "undefined value for $item" );
}
return $value;
}
package Template::Monad::Assert;
our $EXCEPTION = 'Template::Exception';
our $AUTOLOAD;
sub new {
my ($class, $stash, $this) = @_;
bless [$stash, $this], $class;
}
sub AUTOLOAD {
my ($self, @args) = @_;
my ($stash, $this) = @$self;
my $item = $AUTOLOAD;
$item =~ s/.*:://;
return if $item eq 'DESTROY';
my $value = $stash->dotop($stash, $item, \@args);
if (! defined $value) {
die $EXCEPTION->new( assert => "undefined value for $item" );
}
return $value;
}
1;
__END__
=head1 NAME
Template::Plugin::Assert - trap undefined values
=head1 SYNOPSIS
[% USE assert %]
# throws error if any undefined values are returned
[% object.assert.method %]
[% hash.assert.key %]
[% list.assert.item %]
=head1 DESCRIPTION
This plugin defines the C<assert> virtual method that can be used
to automatically throw errors when undefined values are used.
For example, consider this dotop:
[% user.name %]
If C<user.name> is an undefined value then TT will silently ignore the
fact and print nothing. If you C<USE> the C<assert> plugin then you
can add the C<assert> vmethod between the C<user> and C<name> elements,
like so:
[% user.assert.name %]
Now, if C<user.name> is an undefined value, an exception will be thrown:
assert error - undefined value for name
=head1 AUTHOR
Andy Wardley E<lt>abw@wardley.orgE<gt> L<http://wardley.org/>
=head1 COPYRIGHT
Copyright (C) 2008-2022 Andy Wardley. All Rights Reserved.
This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
=head1 SEE ALSO
L<Template::Plugin>
=cut
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