tracking down a test issue - ResourceWarning: unclosed file <_io.BufferedRandom

[Jonathan Vanasco]

I keep encountering a particular `ResourceWarning: unclosed file <_io.BufferedRandom` in my test suite that I can not track down.  I'm hoping someone else may have an idea:

* In a suite of 10+ test classes, it only happens when 2 particular classes are run consecutively and in a particular order. It does not happen in the inverse.  
* this happens in a testapp setup, on the consecutive setup
* the error happens in this stack:

    pyramid.paster.get_appsettings("test.ini")
    ...
    plaster.loaders.find_loader()

It seems to trigger right after the final `return [EntryPointLoaderInfo...] 

The error is also coming from `packaging/version.py`

site-packages/pkg_resources/_vendor/packaging/version.py:141: ResourceWarning: unclosed file <_io.BufferedRandom name=5>

and is in the _cmpkey function:

    release = tuple(

        reversed(list(

            itertools.dropwhile(

                lambda x: x == 0,

                reversed(release),

            )

        ))

    )

I can't seem to recreate this, and I can't pinpoint things further to fix.  It happens somewhere in the pyramid/plaster/paste configuration.  

Does this situation look familiar to anyone?  This makes no sense.  I have a small hope that someone has experienced this before and knows where I should be focusing my efforts.

[Jonathan Vanasco]

After even more testing (half my day!)...

My app needed an `add_finished_callback` to close any `webob.compat.cgi_FieldStorage` objects in forms.

[Michael Merickel]

If you're opening files you should use the context manager - for example:

with request.POST['file'] as field:

    data = field.file.read()

On Tue, Feb 4, 2020 at 3:53 PM Jonathan Vanasco <jona...@findmeon.com> wrote:

After even more testing (half my day!)...

My app needed an `add_finished_callback` to close any `webob.compat.cgi_FieldStorage` objects in forms.

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Michael

[Jonathan Vanasco]

On Wednesday, February 5, 2020 at 1:15:23 PM UTC-5, Michael Merickel wrote:

If you're opening files you should use the context manager - for example:

with request.POST['file'] as field:

    data = field.file.read()

Thanks, Michael. My application code did that... but somewhere in the form management/validation stack, file objects were being opened and not closed.  I haven't tracked down exactly where that happens yet, so I went with the finished callback to close file-like objects.