Function observableMapGetOrCreate

core/queryIndex.ts:40–55

* Will get existing value or create new one from observable map.

(
  map: ObservableMap<K, V>,
  key: K,
  getter: () => V
)

 * Will get existing value or create new one from observable map.
 */
function observableMapGetOrCreate<K, V>(
  map: ObservableMap<K, V>,
  key: K,
  getter: () => V
): V {
  if (map.has(key)) {
    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
    return map.get(key)!;
  }

  const newValue = getter();

  map.set(key, newValue);

  return newValue;
}

/**
 * Will create unique key index for entity store that will automatically add/update/delete items from the index on changes.