http://www.perlmonks.org?node_id=701312

rustycar has asked for the wisdom of the Perl Monks concerning the following question:

Sorry in advance for such a long post here...

I'm using select() to select an item from a 'select' list (duh! :-) - but I do not know ahead of time what the names of said items are.

So, I wrote something like this:
my $ans = 1; # or whatever. while ($ans) { %pickme = ( n => 1 ); #yes, this should be outside the while. So s +ue me ;-) $ans = $mech->select( 'server', \%pickme ); if ($ans) { $inputobj = $mech->current_form()->find_input( 'remove', 'subm +it'); die 'argh! Cannot find delete button on the iSCSI Access page! +' unless $inputobj; $ans = $mech->click_button( input => $inputobj ); } } print "Done! Now, accept the empty list\n"; # ok, now accept a (hopefully) empty list of allowed accessors $inputobj = $mech->current_form()->find_input( 'accept', 'submit'); die 'argh! Cannot find Accept button on the iSCSI Access page!' unless + $inputobj; $ans = $mech->click_button( input => $inputobj );
However, it turns out that select will ALWAYS think that it can select entry 1, even if the list is empty. In other words, even when the html looks like this:
<td> <input type="hidden" name="serverList" value=""> <select size="10" name="server" style="width: 330px"> </select> </td>
The above code will get '1' back from select and go running on forever. Not a good thing...

I discovered that if entry 2 didn't exist, and you tried to select THAT entry you'd get an appropriate error, so I ended up with this as a workaround:
while ($ans) { %pickme = ( n => 2 ); eval { $ans = $mech->select( 'server', \%pickme ); }; if ($ans eq 1) { $inputobj = $mech->current_form()->find_input( 'remove', 'subm +it'); die 'argh! Cannot find delete button on the iSCSI Access page! +' unless $inputobj; $ans = $mech->click_button( input => $inputobj ); } else { $ans = 0; } } %pickme = ( n => 1 ); $ans = $mech->select( 'server', \%pickme ); $inputobj = $mech->current_form()->find_input( 'remove', 'submit'); die 'argh! Cannot find delete button on the iSCSI Access page!' unless + $inputobj; $ans = $mech->click_button( input => $inputobj ); print "Done! Now, accept the empty list\n"; # ok, now accept a (hopefully) empty list of allowed accessors $inputobj = $mech->current_form()->find_input( 'accept', 'submit'); die 'argh! Cannot find Accept button on the iSCSI Access page!' unless + $inputobj; $ans = $mech->click_button( input => $inputobj );
It seems to me that the first form should have worked (see the Mechanize page under select() for details of why - won't bore everyone here with that), so I'm looking at the Mechanize and Form code to see why it allows a 'select' of 1 when there are no items.

I've looked at WWW::Mechanize, and the issue seems to be in Form instead. Here is the section that seems to be involved here:
for (@{$self->{menu}}) { if ((defined($val) && defined($_->{value}) && $val eq $_-> +{value}) || (!defined($val) && !defined($_->{value})) ) { $cur = $i; $disabled = $_->{disabled}; last unless $disabled; } $i++; }
When there is nothing in the select list, the above test still passes! I note, when stepping through the code, that if I print $val when I'm looking at the 'big if' above, I get a blank line, BUT defined($val) is true!

So, am I just confused, is the above test wrong, is my code wrong, or ???

(Conclusion: the HTML is wrong - its illegal to have a select with no option. You should have a single empty option, and detect that its an empty option (I'll have to RTFM for how to do that, but that's just Fine :-)

Thanks!

Final comment - thanks to Hermit (psini for his/her help - and sorry for not thinking to RTFM on how HTTP select fields work, once the comment was made (too focussed on Mechanize::select and figuring out how to get around having no (obvious) way to tell when there's nothing there....

Anyway, I consider this thread finished (and now I know what bug to file with the authors). I've modified the subject, at the suggestion of ambrus, to make it better. Thanks again!