gh-156434: Restore entry offsets when repack() fails - #156435
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_ZipRepacker.repack() updates ZipInfo.header_offset for each member before moving that member's bytes, so a failing _copy_bytes() left the in-memory offsets describing a layout that was never written. remove() has already set _didModify, so a later close() committed a central directory built from those offsets, and the archive became unreadable even though the caller had handled the error. ZipFile.repack() now snapshots the offsets of the surviving and the removed entries and restores them if the repack raises. The copy only ever moves data to lower offsets, so a partial move never overwrites its own source and the archive falls back to the state of a remove() with no repack().
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ZipFile.repack()now saves theheader_offsetof every entry it hands to the repacker, including the removed ones, and restores them if the repack raises. A failed move no longer leaves the in-memory offsets describing a layout that was never written, so a laterclose()no longer commits it.No changelog entry:
remove()andrepack()are new in 3.16 and have not been released, so this belongs with the original entry for gh-51067.ZipFile.close()writes wrong offsets after a failedrepack()#156434