Keyed client layer (source xs key id = q.rows) replaces every row object on each answer (IMMUTABLE_UPDATE_IN_STORE) #51

Filed with Opus 5.5. I personally don't have the required understanding to know whether it's something worth fixing, but I had a stab at converting my web app to use reactivescript. Very excited for the development, so I'll continue to file (hopefully) useful issues, based on the migration efforts

Versions: 0.1.0 and main at 08255de, solid-js 2.0.0-rc.21.

source xs key id = q.rows lowers to createOptimisticStore(draft => assignDraft(draft, …), [], { key }). For arrays, assignDraft does draft.length = v.length; v.forEach((x, i) => { draft[i] = x }), so every row is replaced by a fresh object on every answer. That includes a refresh that returns identical data.

Solid's dev runtime warns for each row:

[IMMUTABLE_UPDATE_IN_STORE] "store.0" was replaced with a fresh object whose leaves are mostly the same values (15 of 19 unchanged, 4 changed) — … For data arriving from outside (a fetch result), merge it with reconcile(data, key)(store.0).

Effect: what renders is correct, but every reader of every row re-runs on every answer. In our app (a booking grid with one keyed source of bookings) that means every card re-renders on each refresh and after each save.

Suggestion: merge the answer by the declared key, e.g. reconcile(v, key)(draft), as the warning recommends, instead of assigning rows. I haven't tested whether returning the value from the derive (letting Solid diff it by key) works equally well here.