[cgiapp] Unexpected variable persistence with CAD / CADS

[Richard Jones]

Using CGI::Application::Dispatch with CGI::Application::Dispatch::Server

Editing a record with: <form method="post" action="/foo/update/2">
# form contains record #2 data

CAD table is configured as :app/:rm/:id, so the request is handled by 
Foo::update

###################
package Foo;
sub update {
   my $self = shift;
   my $vars = $self->query->Vars;

   if ( my $id = $self->param('id') ) {
     $vars->{id} = $id; # should only contain a value if an update req.
   }
   # update db with content of $vars;
}
####################

This works as intended - updates record #2. But if my next action is to 
request a form to create a new record - eg http://localhost:8080/foo -

<form method="post" action="/foo/new_record">
# form populated with new data unrelated to previous edit

on submission of the form, instead of getting a new record created I get 
an update of an existing record, which gets clobbered with the new 
incoming data. That's because $vars{id} (generated in same way as above) 
contains the value of the previous action id.

With CAD debugging switched on, for an unrelated url request, for 
example http://localhost:8080/bar, console output is:
Final args to pass to new(): $VAR1 = {
   'PARAMS' => {
     'config_files' => [
       './config/config.pl',
       './config/validation.pl'
     ],
     'id' => '2' ###### <==
   }
};

That value of 'id' (2 in this case) persisted from the previous action, 
  and will continue to live indefinitely across multiple requests until 
it is either superceded by another id, or until I re-start the CAD server.

The solution (so far) is to avoid the use of $self->param('id') entirely 
and pass the id in as a hidden form field. But that partly defeats the 
functionality of the CAD table declaration.

I can't work out why the id param is being retained across requests like 
this, whether it's a problem related to using CAD/CAD::Server, or 
something I've overlooked in my app or CAD setup. But as it stands it is 
potentially lethal as it will sooner or later update the wrong record.
-- 
Richard Jones