Function mergeParentThings

src/ui-solid/Provider.tsx:30–44

(
  offset: Offset,
  parentValue: ContextValue,
  defaultThing: ThingsByOffset[Offset] | undefined,
  thingsById: ThingsById<ThingsByOffset>[Offset] | undefined,
  extraThingsById: ExtraThingsById,
)

export const OFFSET_SYNCHRONIZER = 7;

const mergeParentThings = <Offset extends Offsets>(
  offset: Offset,
  parentValue: ContextValue,
  defaultThing: ThingsByOffset[Offset] | undefined,
  thingsById: ThingsById<ThingsByOffset>[Offset] | undefined,
  extraThingsById: ExtraThingsById,
): [ThingsByOffset[Offset] | undefined, ThingsById<ThingsByOffset>[Offset]] => [
  defaultThing ??
    (parentValue[offset * 2] as ThingsByOffset[Offset] | undefined),
  {
    ...parentValue[offset * 2 + 1],
    ...thingsById,
    ...extraThingsById[offset],
  },
];

const EMPTY_CONTEXT = () => [] as ContextValue;