Function subsetEqualityWithContext

packages/expect/src/jest-utils.ts:619–648

(seenReferences: WeakMap<object, boolean> = new WeakMap())

  // there are circular references in the subset passed to it.
  const subsetEqualityWithContext
    = (seenReferences: WeakMap<object, boolean> = new WeakMap()) =>
      (object: any, subset: any): boolean | undefined => {
        if (!isObjectWithKeys(subset)) {
          return undefined
        }

        return Object.keys(subset).every((key) => {
          if (subset[key] != null && typeof subset[key] === 'object') {
            if (seenReferences.has(subset[key])) {
              return equals(object[key], subset[key], filteredCustomTesters)
            }

            seenReferences.set(subset[key], true)
          }
          const result
            = object != null
              && hasPropertyInObject(object, key)
              && equals(object[key], subset[key], [
                ...filteredCustomTesters,
                subsetEqualityWithContext(seenReferences),
              ])
          // The main goal of using seenReference is to avoid circular node on tree.
          // It will only happen within a parent and its child, not a node and nodes next to it (same level)
          // We should keep the reference for a parent and its child only
          // Thus we should delete the reference immediately so that it doesn't interfere
          // other nodes within the same level on tree.
          seenReferences.delete(subset[key])
          return result
        })
      }

  return subsetEqualityWithContext()(object, subset)
}