Function getObjectSubset

packages/expect-utils/src/utils.ts:116–167

(
  object: any,
  subset: any,
  customTesters: Array<Tester> = [],
  seenReferences: WeakMap<object, boolean> = new WeakMap(),
)

// printing the diff for toMatchObject() without adding unrelated noise.
/* eslint-disable @typescript-eslint/explicit-module-boundary-types */
export const getObjectSubset = (
  object: any,
  subset: any,
  customTesters: Array<Tester> = [],
  seenReferences: WeakMap<object, boolean> = new WeakMap(),
): any => {
  /* eslint-enable @typescript-eslint/explicit-module-boundary-types */
  if (Array.isArray(object)) {
    if (Array.isArray(subset) && subset.length === object.length) {
      // The map method returns correct subclass of subset.
      return subset.map((sub: any, i: number) =>
        getObjectSubset(object[i], sub, customTesters),
      );
    }
  } else if (object instanceof Date) {
    return object;
  } else if (isObject(object) && isObject(subset)) {
    if (
      equals(object, subset, [
        ...customTesters,
        iterableEquality,
        subsetEquality,
      ])
    ) {
      // Avoid unnecessary copy which might return Object instead of subclass.
      return subset;
    }

    const trimmed: any = {};
    seenReferences.set(object, trimmed);

    for (const key of getObjectKeys(object)) {
      if (!hasPropertyInObject(subset, key)) {
        continue;
      }

      trimmed[key] = seenReferences.has(object[key])
        ? seenReferences.get(object[key])
        : getObjectSubset(
            object[key],
            subset[key],
            customTesters,
            seenReferences,
          );
    }

    if (getObjectKeys(trimmed).length > 0) {
      return trimmed;
    }
  }
  return object;
};

const IteratorSymbol = Symbol.iterator;