[Catalyst] Where is the form field lost?

[Octavian Rasnita]

Hi,

After sending a form with a file upload field, that field is lost if no file
was attached, just like when the form doesn't contain that file upload field
at all.

I have tried to check Catalyst, Catalyst::Request, Catalyst::Engine,
HTTP::Body and HTTP::Body::MultiPart in order to find where are the file 
upload fields lost, but I
couldn't find it.

I need to know if the form didn't have a file upload field, or if it had it
but no file was uploaded.

I have printed Dumper $request->_body in Catalyst::Engine::prepare_uploads,
and when a file is uploaded, it looks like:

$VAR1 = bless( {
                 'content_length' => '1727',
                 'tmpdir' => 'C:\\DOCUME~1\\Octavian\\LOCALS~1\\Temp',
                 'part' => {},
                 'buffer' => '',
                 'state' => 'done',
                 'chunk_buffer' => '',
                 'body' => undef,
                 'content_type' => 'multipart/form-data;
boundary=---------------------------7da8c3070458',
                 'length' => 1727,
                 'boundary' => '---------------------------7da8c3070458',
                 'chunked' => '',
                 'upload' => {
                               'file' => {
                                           'headers' => {
                                                          'Content-Type' =>
'text/plain',
                                                          'Content-Disposition'
=> 'form-data; name="file"; filename="E:\\zzzz_cool.txt"'
                                                        },
                                           'tempname' =>
'C:\\DOCUME~1\\Octavian\\LOCALS~1\\Temp\\PrJ0ruNzzR',
                                           'name' => 'file',
                                           'size' => 44,
                                           'filename' => 'E:\\zzzz_cool.txt'
                                         }
                             },
                 'param' => {},
               }, 'HTTP::Body::MultiPart' );


If no file was uploaded, it prints:

$VAR1 = bless( {
                 'content_length' => '1699',
                 'tmpdir' => 'C:\\DOCUME~1\\Octavian\\LOCALS~1\\Temp',
                 'part' => {},
                 'buffer' => '',
                 'state' => 'done',
                 'chunk_buffer' => '',
                 'body' => undef,
                 'content_type' => 'multipart/form-data;
boundary=---------------------------7da1573870458',
                 'length' => 1699,
                 'boundary' => '---------------------------7da1573870458',
                 'chunked' => '',
                 'upload' => {},
                 'param' => {},
               }, 'HTTP::Body::MultiPart' );

So the 'upload' key doesn't contain anything, not even the name of the file
upload field.

Can you give me a hint where I should look for finding where the empty file
upload field is skipped if it is empty?

Thank you.

Octavian