fix: DBObjectDirectoryAdapter lost objects written just before a read

[gmpassos]

Fixes the Pagination [objectAdapter] flake that has been failing test_vm on master.

Root cause

DBObjectDirectoryAdapter._saveObject was async and did File.writeAsString, but both callers — doInsert and doUpdate — dropped the returned Future:

_saveObject(table, id, entry);      // Future<void>, never awaited

return _finishOperation(op, id, preFinish);

Every reader in that class inspects the filesystem synchronously (listSync, existsSync), so there was no happens-before relationship between a store completing and its object being on disk.

The failure is silent rather than loud. _doSelectAllImpl lists the directory, reads each entry, and passes the result through resolveAllNotNull(). A file that hasn't landed yet reads back as null and is simply discarded — so selectAll returns fewer objects, with no error.

analysis_options.yaml sets discarded_futures: false, which is why the dropped Future was never flagged.

Why this is the flake

The test stores in the order PG-03, PG-01, PG-05, PG-02, PG-04, then asserts all five come back. Observed CI failures:

Run	Actual	Missing
master @ 4caf237	[PG-01, PG-03, PG-05]	PG-02, PG-04
PR #148	[PG-01, PG-02, PG-03, PG-05]	PG-04

The entries that vanish are always the most recently stored ones, and which ones vary per run — exactly what an unfinished write produces. It never reproduces on a fast local disk, which is why it only ever showed up on CI.

Confirmed by experiment: inserting a 30 ms delay before the un-awaited write reproduces that exact assertion failure locally, on every group:

Expected: ['PG-01', 'PG-02', 'PG-03', 'PG-04', 'PG-05']
  Actual: []

The fix

Make the write synchronous, consistent with every other filesystem operation in the class (listSync, existsSync, createSync, deleteSync):

void _saveObject(String table, Object? id, Map<String, dynamic> obj) {
  var file = _resolveObjectFile(table, id);
  var enc = dart_convert.json.encode(obj);
  file.writeAsStringSync(enc);
}

This is a correctness fix, not just a test fix: any caller that stored an object and then read it back could miss it.

Testing

Adds DBObjectDirectoryAdapter > a stored object is immediately visible, asserting the store→read invariant.

Being straight about its limits: it only fails where the write is slow enough to lose the race, so it does not fail on a fast local disk. It is a cheap statement of the invariant; Pagination [objectAdapter] remains the test that actually catches this, and it should now be stable.

Gate	Result
dart test --exclude-tags docker	688 passed
dart test test/bones_api_entity_db_directory_test.dart ×3	53 passed each
dart analyze --fatal-infos --fatal-warnings .	clean
dart format -o none --set-exit-if-changed .	clean

Docker-tagged suites not run locally (no daemon); they don't touch this adapter.

Note, not fixed here

_listTableFiles filters hidden files with !path.startsWith('.'), but path is the absolute path, so that check is always false — it was presumably meant to test the basename. Harmless today (a hidden file would still need to end in .json), and unrelated to this bug, so I left it alone rather than mix an unrelated behavior change into a flake fix.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.76%. Comparing base (4c108a0) to head (efdaa5e).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #149      +/-   ##
==========================================
- Coverage   67.77%   67.76%   -0.01%     
==========================================
  Files          64       64              
  Lines       21607    21607              
==========================================
- Hits        14644    14642       -2     
- Misses       6963     6965       +2     

Flag	Coverage Δ
unittests	67.76% <100.00%> (-0.01%)	⬇️

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