solidjs / solid / 39116943184

78%

main: 89%

push

github

perf(web): fix #574 by bounding the reconciler's suffix walk, not a per-row liveness check (#4133)

* perf(web): the reconciler's prefix and suffix walks skip the per-node liveness check

The suffix walk is bounded to the open range [aStart, aEnd); inside that
range this pass never detaches a node, so neither walk needs isLive. The
bound alone closes #574, where the unbounded suffix walk reached back past
aStart to a node a map-branch replace had taken out while it was still
pending in b. Every anchor read and destructive branch keeps its ownership
gate.

Measured with the call profiler on the Octane js-framework fixture, swap of
rows 1 and 998 in 1000: 29.5 -> 25.0 µs (Vapor 9.0). reconcileArrays
inclusive 24.4 -> 13.8 µs; isLive (8.4 µs self) gone. uibench through the
board runner, oracle identical to the previous run (96 cases, 32,543 shared
identities): tree/[500] virtual_dom_worst_case -17%, snabbdom_worst_case
-14%, moveFromEndToStart -11%, tree removeAll -7 to -11%, reverse flat.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

* fix(web): the append branch anchors on a live node when the walks skipped a migrated one

Review on #4133: with the per-node check gone from the prefix and suffix
walks, the node the append branch anchors on can be one user code moved
away. `reconcileArrays(p, [x], [y, x])` with x detached threw NotFoundError
from insertBefore, which halts reactivity; through insert, rendering [z, x],
moving x into a modal and then rendering [y, x] left the slot empty.

The suggested `isLive(b[bEnd]) ? b[bEnd] : after` stops the throw but lands
the insert past the live suffix when the migrated node is not the suffix's
last, and the bStart branch had the same fallback when the node before the
insert is the migrated one. The anchor is now the last live prefix node's
successor, else the first suffix node still ours, else `after`. The walks
stay check-free; the loop runs only in the append branch and stops at its
first live node,... (continued)

756 of 1050 branches covered (72.0%)

Branch coverage included in aggregate %.

1097 of 1339 relevant lines covered (81.93%)

27.71 hits per line