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Settings sync: sync engine with revision conflict handling #986
Description
Part of cross-device settings sync for Switchify PC.
Scope
- Download on sign-in and app start. Upload 3 s after any settings save, waiting until changes stop.
- Avoid lost writes with revision checks:
PATCH ...?revision=eq.N, and if no row matches, download again and resolve. - On first sign-in, if both this PC and the cloud have customised settings, ask whether to keep this PC's settings or use the cloud copy. Never overwrite silently.
- Keep working offline, retry with backoff, and show sync status in the UI.
- Never log the contents of the settings document.
Acceptance
- Tests against a fake back end covering conflicts, offline retry, the first-sign-in prompt and sign-out.
Activity
enaboapps commentedon Oct 5, 2026
Notes from the Supabase review (switchifyapp/switchify-supabase#2), for the client contract:
POST. A409/23505means another device created it first; fall back to GET thenPATCH.PATCH ?revision=eq.NandPrefer: return=representation. An empty result means a conflict.merge-duplicates/on_conflict), because an upsert bypasses the revision check. Clients have no DELETE permission.user_id. After an account is deleted and recreated, the new row starts at revision 1 under a new uid, so a cache from the old account must never be applied to the new one.enaboapps commentedon Oct 5, 2026
Notes from the #989 review, for the sync engine:
portable_settings::applyon the main thread (run_on_main_thread, likeconfigure_point_scan).applycan partly succeed, for example when a file write fails or a switch capture is active. Treat an error as retryable: re-running it with the same document converges.AppState, soemit_statewon't refresh the Profiles screen. Emit a profiles-changed event, or have the UI refetchlist_switch_profiles, after a sync applies profiles.ParseError::Newermeans the cloud copy came from a newer app. Show the "update Switchify PC" message and don't upload over it.enaboapps commentedon Oct 5, 2026
One more note from the #989 review: parsing requires an exact JSON round trip, and the document contains explicit
nulls. Never strip nulls on the way to or from storage (nojsonb_strip_nulls, and no client that drops null fields), or every document will fail to parse. Add a test that round-trips through the real column.