Empty files on S3 after gzipping with Django 1.11 (s3boto)

[melwas]

In Django 1.11.x there was a change in collectstatic command (here).

I noticed that after upgrade there is an issue with files uploaded to S3 when GZIP is enabled. Some files (post-processed by ManifestFilesMixin and used in its manifest file) are uploaded as empty files.

I found that there is a potential issue with _compress_content method in S3Boto3Storage class.

Currently, the method looks like this:

zbuf = BytesIO()
zfile = GzipFile(mode='wb', compresslevel=6, fileobj=zbuf)
try:
    zfile.write(force_bytes(content.read()))
finally:
    zfile.close()
zbuf.seek(0)
return zbuf

When I use the storage and also use ManifestFilesMixin from Django the content.read() returns an empty bytes object. If I add content.seek(0) before everything works as expected.

When I revert to Django 1.10.7 everything also works as expected. When I disable gzipping the files are also uploaded correctly.

[jschneier]

A failing test case would be very helpful here. From reading the linked to Django changelog backwards incompat log it reads as though you have an issue on your side although I might be misunderstanding it.

[melwas]

@jschneier I added a failing test with explanation :)

[jmichalicek]

Just confirming this issue. I ran into it and tracked it down very shortly after Django 1.11 was released, but got sidetracked and did not get it reported.

[jschneier]

Fixed in #373. Will release shortly.