Bug report

Proposal:

Today ourzipfile module internal implementation uses a heuristic dance to determine when a zip64 header is likely to be required betweenzipfile.ZipFile._open_to_write() andzipfile._ZipWriteFile.close().

This seems rather silly. Any the timezipfile._ZipWriteFile.close() is called, we know thereal uncompressed and compressed data sizes and can deterministically decide at that time. Instead of the existing heuristic of "if the expected input file_size * 1.05 > ZIP64_LIMIT" used within_open_to_write() today.

The only time we should ever raise an exception regarding zip64 being requires is if the API user has explicitly forbidden zip64's use.

I wouldn't backport this change to a stable release as it will alter the exact output produced in some circumstances (zip64 headers will no longer be added unnecessarily in borderline cases where they were not needed), but it is fair to consider it more of a bug that removes an odd API internal implementation wart as well as a feature.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response