bind_columns changes input to after_parse callback

[djerius]

Binding columns effectively hides the input data from the after_parse callback. For example,

#! perl

use v5.10;
use strict;
use warnings;

use Text::CSV;

my $data = <<EOF;
col1,col2,col3
val1,val2,val3
EOF

use Data::Dumper;

my $csv = Text::CSV->new( { callbacks => {after_parse => sub {say Dumper $_[1]; }} } );
my $fh;

open $fh, '<', \$data;
1 while $csv->getline( $fh );

my @row = (undef) x 3;
$csv->bind_columns( \( @row ) );

open $fh, '<', \$data;
1 while $csv->getline( $fh );

Results in:

$VAR1 = [
          'col1',
          'col2',
          'col3'
        ];

$VAR1 = [
          'val1',
          'val2',
          'val3'
        ];

$VAR1 = [];

$VAR1 = [];

I don't think there's any way around this without copying the data (as the parsed data are no longer stored in an array that's controlled by Text::CSV) which defeats the purpose of bind_columns.

I haven't looked into how this affects all of the callbacks; at least for after_parse there's a workaround:

after_parse => sub {
    my @refs = $_[0]->bind_columns;
    if ( defined $refs[0] ) {
        say Dumper ${$_} for @refs;
    }
    else {
        say Dumper $_[1];
    }
}

The documentation doesn't mention this side effect. While it's somewhat obvious after you're bitten by it, it'd be useful if the documentation indicated where it comes into play.

Thanks!