Making Nested UI Re-renders O(1) — read-model, external store, and render-count tests
In an immutable-tree editor, editing a single line redrew everything; here's how I first pinned the problem with a test, then cut row and container re-renders with a normalized projection and per-id subscriptions
- An immutable tree patch gives ancestors a new ref too, so passing props down triggers O(depth) re-renders — a normalized entry plus per-id subscription can cut it to O(1)
- The entry cache must be stabilized by output value-equality, not input ref, and the external store sync must run synchronously at the choke point right before setState