Un(der)documented bits of cgi.py

[Bob Kline]

I'm trying to detect and intelligently deal with problems created when a 
user of a Python CGI page uploads a file and then gets impatient and 
clicks on some other button or the browser's cancel button (or even 
closes the page).  If the file is large enough, and the user is 
impatient enough, this can result in the FieldStorage.file object 
getting some, but not all of the bytes from the user's file, with no 
documented means of detecting that this has happened.  Poking around in 
the code for cgi.py in the standard library, it appears that there is an 
undocumented 'done' attribute which might be useful here (it seems as if 
it might get set to -1 when this condition is encountered), but of 
course one is reluctant to leave behind software which relies on 
undocumented behavior of packages, since those bits have a way of 
disappearing in the middle of the night, suddenly breaking one's 
software.  Can anyone think of a good reason why it would not be 
desirable to expose a publicly documented means of detecting the 
condition described above?

Cheers and thanks!
Bob Kline