Function reconcile

packages/core/src/render3/list_reconciliation.ts:111–353

(
  liveCollection: LiveCollection<T, V>,
  newCollection: Iterable<V> | undefined | null,
  trackByFn: TrackByFunction<V>,
  reactiveConsumer: ReactiveNode | null,
)

 *     occur when accessing the length or iterator are tracked.
 */
export function reconcile<T, V>(
  liveCollection: LiveCollection<T, V>,
  newCollection: Iterable<V> | undefined | null,
  trackByFn: TrackByFunction<V>,
  reactiveConsumer: ReactiveNode | null,
): void {
  let detachedItems: UniqueValueMultiKeyMap<unknown, T> | undefined = undefined;
  let liveKeysInTheFuture: Set<unknown> | undefined = undefined;

  let liveStartIdx = 0;
  let liveEndIdx = liveCollection.length - 1;

  const duplicateKeys = ngDevMode ? new Map<unknown, Set<number>>() : undefined;

  if (Array.isArray(newCollection)) {
    setActiveConsumer(reactiveConsumer);
    let newEndIdx = newCollection.length - 1;
    setActiveConsumer(null);

    while (liveStartIdx <= liveEndIdx && liveStartIdx <= newEndIdx) {
      // compare from the beginning
      const liveStartValue = liveCollection.at(liveStartIdx);
      const newStartValue = newCollection[liveStartIdx];

      if (ngDevMode) {
        recordDuplicateKeys(duplicateKeys!, trackByFn(liveStartIdx, newStartValue), liveStartIdx);
      }

      const isStartMatching = valuesMatching(
        liveStartIdx,
        liveStartValue,
        liveStartIdx,
        newStartValue,
        trackByFn,
      );
      if (isStartMatching !== 0) {
        if (isStartMatching < 0) {
          liveCollection.updateValue(liveStartIdx, newStartValue);
        }
        liveStartIdx++;
        continue;
      }

      // compare from the end
      // TODO(perf): do _all_ the matching from the end
      const liveEndValue = liveCollection.at(liveEndIdx);
      const newEndValue = newCollection[newEndIdx];

      if (ngDevMode) {
        recordDuplicateKeys(duplicateKeys!, trackByFn(newEndIdx, newEndValue), newEndIdx);
      }

      const isEndMatching = valuesMatching(
        liveEndIdx,
        liveEndValue,
        newEndIdx,
        newEndValue,
        trackByFn,