[issue10093] Warn when files are not explicitly closed

[Antoine Pitrou]

Antoine Pitrou <pitrou at free.fr> added the comment:

> That's what I'm referring to: most Python applications are
> written with the fact in mind, that garbage collection will
> close the files or socket.
> 
> That's a perfectly fine way of writing Python applications,

Some people would disagree, especially Windows users who cannot timely
delete files when some file descriptors still point to them.

> so why should the programmer get warned about this regular
> approach to Python programming ?

Again: it is an *optional* warning. It is *disabled* by default, except
when compiled --with-pydebug.

> The same applies for sockets.

It is *definitely* a mistake if the socket has been bound to a local
address and/or connected to a remote endpoint.

> Think of the simple idiom:
> 
> data = open(filename).read()
> 
> This would always create a warning under the proposal.

We have had many Windows buildbot failures because of such coding style.

> If you want to monitor resource usage in your application it
> would be a lot more useful to provide access to the number of
> currently open FDs

Agreed it would be useful as well, but please tell that to operating
system vendors. Python has no way to calculate such a statistic.

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