[Html-widget] HTML::Widget::Constraint::Range wherein limit is zero

[Steven Kuo]

It's should be possible to set a constraint
with H::W::C::Range wherein the
minimum or maximum is zero, right?

But in order to register this constraint
it seems I have to use a "zero-but-true"
specification.  It's not clear from the documentation
that a plain zero (0) won't work.

Here's a test that I inserted into the
test suite and ran with 'prove':

$ cat t/constraint_range_added.t
use strict;
use warnings;

use Test::More tests => 4;

use HTML::Widget;
use lib 't/lib';
use HTMLWidget::TestLib;

my $w1 = HTML::Widget->new;
my $w2 = HTML::Widget->new;

$w1->element( 'Textfield', 'foo' );
$w1->constraint( 'Range', 'foo' )->min("0e0"); # zero-but-true

$w2->element( 'Textfield', 'bar' );
$w2->constraint( 'Range', 'bar' )->min(0);

#
{
    my $query = HTMLWidget::TestLib->mock_query(
        {
            foo => -1,
            bar => -1,
        }
    );

    my $f1 = $w1->process($query);
    my $f2 = $w2->process($query);

    is( $f1->param('foo'), undef, 'undef returned for invalid' );
    ok( $f1->errors, 'errors expected: -1 is not >= 0' );

    is( $f2->param('bar'), undef, 'undef returned for invalid' );
    ok( $f2->errors, 'errors expected: -1 is not >= 0' );

}



$ prove -Iblib/lib -v t/constraint_range_added.t
t/constraint_range_added....1..4
ok 1 - undef returned for invalid

ok 2 - errors expected: -1 is not >= 0

#   Failed test 'undef returned for invalid'
#   in t/constraint_range_added.t at line 34.
not ok 3 - undef returned for invalid
#          got: '-1'
#     expected: undef

#   Failed test 'errors expected: -1 is not >= 0'
#   in t/constraint_range_added.t at line 35.
not ok 4 - errors expected: -1 is not >= 0
# Looks like you failed 2 tests of 4.
dubious
        Test returned status 2 (wstat 512, 0x200)
DIED. FAILED tests 3-4
        Failed 2/4 tests, 50.00% okay
Failed Test                Stat Wstat Total Fail  List of Failed
-------------------------------------------------------------------------------
t/constraint_range_added.t    2   512     4    2  3-4
Failed 1/1 test scripts. 2/4 subtests failed.
Files=1, Tests=4,  1 wallclock secs ( 0.28 cusr +  0.07 csys =  0.35 CPU)
Failed 1/1 test programs. 2/4 subtests failed.



The underlying reason is that the 'validate' subroutine
in H::W::C::Range only checks if the limits ( $minimum
and $maximum) are *logically true* (lines 53 and 56):

     42 sub validate {
     43     my ( $self, $value ) = @_;
     44
     45     return 1 if !defined $value || $value eq '';
     46
     47     my $minimum = $self->minimum;
     48     my $maximum = $self->maximum;
     49     my $failed  = 0;
     50
     51     $failed++ if !looks_like_number($value);
     52
     53     if ( !$failed && $minimum ) {
     54         $failed++ unless ( $value >= $minimum );
     55     }
     56     if ( !$failed && $maximum ) {
     57         $failed++ unless ( $value <= $maximum );
     58     }
     59     return !$failed;
     60 }


0, while it's (or should be) a valid limit, is none-the-less
logically (i.e., in boolean context) false.  Hence, I'm finding
myself to use "0e0" instead.

Comments?