Zip files fail to expand on OSX

[rschroll]

We've noticed that the zip files produced here fail to expand automatically when double-clicked on some Macs. The user gets a pop-up window saying, "Unable to expand '' into ''. (Error 2 - No such file or directory.)". However, the zip file will unpack just fine on the command line with unzip.

Most reports of this online are connected to too-large zip files (GBs) or corrupt files, but this happens with small files, and they open just fine on the command line. A couple of possibly-relevant issues:

• A ruby zip streamer ran into a problem with their streaming zip files, which was fixed by adjusting some headers in the zip file: https://github.com/fringd/zipline/pull/2. See also the reported issue: https://github.com/fringd/zipline/issues/1.
• A JS zip library encountered this same error message (https://github.com/gildas-lormeau/zip.js/issues/6), and fixed it by tweaking headers as well: https://github.com/gildas-lormeau/zip.js/commit/fb677d8fda1381599731c84845504c68da2946d9.

I'm going to keep poking around here, but I wanted to document what I've found so far.

[rschroll]

I've found that Python produces different zip files depending on whether the output file handle is streaming (no seek method). It looks like OSX is happy with the non-streaming files, but can't deal with the streaming-produced ones.

The file out.zip was created with a standard file handle. It unzips just fine on OSX. In contrast, out-stream.zip was created with a file handle where seek was disabled. It doesn't unzip on OSX.