Function createDerivedCollection

packages/db/tests/query/includes.test.ts:6337–6352

(
      id: string,
      source: ReturnType<typeof createSyncCollection<any>>[`collection`],
      extraFields?: (d: any) => Record<string, unknown>,
    )

    type RawItem = { key: string; _seq: number; [k: string]: unknown }

    function createDerivedCollection(
      id: string,
      source: ReturnType<typeof createSyncCollection<any>>[`collection`],
      extraFields?: (d: any) => Record<string, unknown>,
    ) {
      return createLiveQueryCollection({
        id: `${id}:derived`,
        query: (q: any) =>
          q.from({ d: source }).select(({ d }: any) => ({
            timelineKey: TIMELINE_KEY,
            key: d.key,
            order: coalesce(d._seq, -1),
            ...(extraFields ? extraFields(d) : {}),
          })),
      })
    }

    it(`second insert propagates with 5 sibling chained toArray includes`, async () => {
      const runs = createSyncCollection<RawItem>(`raw-runs`, (r) => r.key)