Fix atomic file writes exposing empty destinations and leaking temp files - #9805
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The basename was cut with byteslice, which can split a multibyte character in half. Filesystems enforcing UTF-8 validity such as APFS then reject the temporary name with EILSEQ. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The temporary file was renamed into place before being closed, so buffered data had not reached the filesystem yet and a concurrent reader could observe an empty destination. A flush failure such as ENOSPC would surface only after the destination had already been replaced. Cleanup also moved to an ensure block, so an interrupt no longer leaks the temporary file. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Gem::AtomicFileWriterrenamed the temporary file into place before closing it, so buffered data had not reached the filesystem yet. A concurrent reader could observe an empty destination, and a flush failure such asENOSPCwould surface only after the destination had already been replaced with a truncated file. Closing before the rename restores the ordering the writer had before it was refactored.The cleanup path had also become
rescue StandardError, so anInterruptfrom Ctrl-C skipped both the unlink and the rename and left.<name>.tmp.<hex>behind. It is back in anensureblock.Basename truncation used
byteslice, which can cut a multibyte character in half and make the temporary file name fail withEILSEQon filesystems that enforce UTF-8 validity such as APFS. It now trims at a character boundary.This file had a single test before. The invariants above are covered now.