createReferenceCount: solid utility to map object to callback result and handle clean up with reference counting

create-reference-count.ts

const referenceCount = createReferenceCount();

function createReferenceCount() {
  const map = new WeakMap<
    object,
    { count: number; dispose: () => void; result: unknown }
  >();
  return function <T>(object: object, cb: () => T, debug?: string) {
    try {
      const node = map.get(object);
      if (node) {
        node.count++;
        return node.result as T;
      }
      return createRoot((dispose) => {
        const result = cb();
        map.set(object, { dispose, count: 1, result });
        return result;
      });
    } finally {
      onCleanup(() => {
        const node = map.get(object)!;
        node.count--;
        if (node.count === 0) {
          node.dispose();
          map.delete(object);
        }
      });
    }
  };
}