react-native-worklets/src/serializableMappingCache.ts

The React Native multithreading library

'use strict';
import { SHOULD_BE_USE_WEB } from './PlatformChecker';
import type { SerializableRef } from './workletTypes';

/**
 * This symbol is used to represent a mapping from the value to itself.
 *
 * It's used to prevent converting a serializable that's already converted - for
 * example a Shared Value that's in worklet's closure.
 */
export const serializableMappingFlag = Symbol('serializable flag');

/*
During a fast refresh, React holds the same instance of a Mutable
(that's guaranteed by `useRef`) but `serializableCache` gets regenerated and thus
becoming empty. This happens when editing the file that contains the definition of this cache.

Because of it, `createSerializable` can't find given mapping
in `serializableCache` for the Mutable and tries to clone it as if it was a regular JS object.
During cloning we use `Object.entries` to iterate over the keys which throws an error on accessing `_value`.
For convenience we moved this cache to a separate file so it doesn't scare us with red squiggles.
*/

const cache = SHOULD_BE_USE_WEB
  ? null
  : new WeakMap<object, SerializableRef | symbol>();

export const serializableMappingCache = SHOULD_BE_USE_WEB
  ? {
      set() {
        // NOOP
      },
      get() {
        return null;
      },
    }
  : {
      set(serializable: object, serializableRef?: SerializableRef): void {
        cache!.set(serializable, serializableRef || serializableMappingFlag);
      },
      get: cache!.get.bind(cache),
    };