Stop mistaking macOS resource-fork sidecars for history files

[taurheim]

What users were seeing

Every macOS user importing a re-zipped export got this:

Found 24 audio history file(s) in ZIP.
Skipped "._Streaming_History_Audio_2015-2017_0.json" — its JSON is malformed or was read incompletely.
… ×12 …
Warning: skipped 12 of 24 file(s) — some of your history is missing from this import.

Nothing was missing. All 12 of their real files parsed fine.

Cause

UploadStep.vue matched history files with an unanchored pattern tested against the full ZIP path:

const audioFilePattern = /Streaming_History_Audio_.*\.json$/;

macOS writes an AppleDouble sidecar — __MACOSX/._<name> — for every entry when an archive is created or re-zipped on a Mac. Those paths end in .json and contain Streaming_History_Audio_, so they matched too. There's exactly one per real file, so the count doubled and every sidecar then failed JSON.parse.

true  Streaming_History_Audio_2015-2017_0.json
true  __MACOSX/._Streaming_History_Audio_2015-2017_0.json   ← should be false

How the telemetry gave it away

user	OS	skipped / total
laurenvickers_	Mac OS X	12 / 24
stupidemorat	Mac OS X	5 / 10
falintouden	Mac OS X	5 / 10
goopy_monkey	Mac OS X	5 / 10

Three tells, none of which fit real corruption:

1. skipped_count was exactly half of total_files, every time — one sidecar per file
2. Every clustered upload.parseJson failure in 30 days came from macOS
3. All 12 of laurenvickers_'s failures landed within 435ms of the parse starting — far too fast for the mobile memory-exhaustion case this path was built for

The Unexpected token ' ', " Ma"... in the Chrome errors is the Mac OS X marker inside the AppleDouble header, not export data.

Fix

Anchor the match to the basename, which drops the ._ sidecars while still allowing the export's own subdirectory:

const audioFilePattern = /^Streaming_History_Audio_.*\.json$/;
const matchingFiles = Object.keys(zip.files).filter((name) => {
  if (zip.files[name].dir) return false;
  const baseName = name.split('/').pop() || name;
  return audioFilePattern.test(baseName);
});

Impact

No data was ever lost — but users were told it was, which is worse than it sounds for a tool whose whole job is moving someone's listening history. It also buried genuine corruption in noise: real damaged-export reports were outnumbered roughly 30:1 by sidecars, and that skip-and-continue path exists precisely to surface the real ones.

Testing

• New test macOS resource-fork sidecars are not mistaken for history files builds a ZIP the way macOS does — two real files plus two __MACOSX/.../._* AppleDouble entries — and asserts 2 files are found, 2 plays imported, and nothing reported as skipped. Verified it fails without the fix (finds 4 files).
• All 6 Import robustness tests pass.
• npm run lint:check 0 errors, npm run build clean.