closed is True right after opening a S3File

[ahumeau]

Hey there!

Description

After updating to 1.14 I encountered the following issue:

storage = S3Storage(bucket_name="my-bucket")
file = storage.open("my-file")
file.closed
> True  # Should be False

Analysis

I pinpointed the issue to commit af91e2c.

The issue it fixes is perfectly legitimate but the way it fixes it introduces this bug.

S3File implements some kind of lazy opening by leveraging the file property (and its _get_file accessor). The file is not actually opened until the file property is first accessed, self._file remains None until then.
With the current closed implementation, self._file being None results in closed returning False even though in this case the file was never closed, it was never even read from.

Proposed fixes

I see two approaches:

• keeping track of whether a S3File is opened of closed through a _closed attribute (for example), setting it to True in S3File.__init__, to False in S3File.close and reading it in S3File.closed
• forcing _file to be defined by calling f.file in S3Storage._open

I have no idea which is better (might be another approach altogether).

NB: might be related to #1308

[jschneier]

Thanks for the comprehensive report, will look into this

[ahumeau]

Thanks @jschneier!