email.message.get_filename() returning not a filename

Bug report

https://docs.python.org/3/library/cgi.html says that the cgi mudule is deprecated and "The FieldStorage class can typically be replaced with ... the email.message module or multipart for POST and PUT."

An HTML form with a file input field must be transmitted as multipart/form-data. Every input field corresponds to a part of that multipart content. The only way to distinguish a file input from another input is via the filename. A file input comes with a filename, while other inputs don't.

The obvious way to check the filename of a part is via the get_filename() function. But its documentation says: "If the header does not have a filename parameter, this method falls back to looking for the name parameter on the Content-Type header." That leaves the function unusable for checking whether a filename is set, because every HTML input field has a name attribute, and therefore the function returns a supposed filename for all input fields, no matter whether they are files or not.

As a workaround, the result of the get_content_disposition() function can be parsed for a filename attribute, but that's unnecessarily complicated and error-prone. That's not what I would expect from a suggested replacement for a module that didn't require any low-level hacking.

For those reasons, the get_filename() function should only return the filename, not the input name. Or the email.message module shouldn't be suggested as a replacement for the FieldStorage class.

Your environment

Currently working with python 3.9 on an Apache webserver

Beginne mit dem Modul email.message und der Dokumentation zu get_filename(), und vergleiche das Verhalten seiner Parameter filename und name mit den Hinweisen zum Ersatz von cgi.FieldStorage. Bestätige das erwartete Verhalten für multipart/form-data-Teile mit und ohne Dateinamen, und aktualisiere anschließend das relevante Verhalten und die Tests, sodass get_filename() einen Eingabenamen nicht als Dateinamen zurückgibt.