solidjs / solid / 34574929185

72%

main: 89%

push

github

perf(signals): narrow store writes clone by spread; overlay only for wide owned backings (#3367)

Part one of #3360. Per write+commit on a one-key store: rc.7 629 ns ->
340 ns steady state; a fresh store's first write+commit 3x cheaper (the
reporter's 100k-store shape ~265 -> ~90 ms).

- cloneRaw spreads plain-data containers (Object.prototype, every own key an
  enumerable data property) instead of the descriptor walk: same result,
  ~1/50th the cost. The one-time accessor scan grades the container (sc
  0/1/2) and records its own-key count (kc, bumped by set-trap writes of new
  keys so a record that grows from {} still graduates).
- The #3044 prototype overlay is taken only for WIDE (>32 keys) containers
  over an OWNED backing. Narrow ones clone cheaper than they overlay
  (Object.create turns the backing into a V8 prototype and every flatten
  writes into that prototype); an unowned backing had to be privatize-cloned
  at commit anyway, so the overlay there paid create + clone + per-key copy.
- Grade-2 containers flatten and take overlay first-writes by bare
  assignment; a non-plain defineProperty through the draft downgrades the
  grade so descriptor-bearing keys keep the descriptor paths.

The remaining per-write cost is the weak-collection registration of each
pending backing (~190 ns); that is part two.

Co-authored-by: Claude via Cursor <noreply@cursor.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

519 of 790 branches covered (65.7%)

Branch coverage included in aggregate %.

772 of 1007 relevant lines covered (76.66%)

15.02 hits per line