Function structuralShare

packages/vue/src/atomQuery.ts:171–183

(
  self: Atom.Atom<AsyncResult.AsyncResult<A, E>>
)

 */
export const replaceEqualDeep = (prev: any, next: any): any => {
  if (prev === next) return prev
  const bothArrays = Array.isArray(prev) && Array.isArray(next)
  if (bothArrays || (isPlainObject(prev) && isPlainObject(next))) {
    const a: Record<PropertyKey, any> = prev
    const b: Record<PropertyKey, any> = next
    const copy: Record<PropertyKey, any> = bothArrays ? [] : {}
    const nextKeys: Array<PropertyKey> = bothArrays ? (b as Array<any>).map((_, i) => i) : Object.keys(b)
    const nextSize = nextKeys.length
    const prevSize = bothArrays ? (a as Array<any>).length : Object.keys(a).length
    let equalItems = 0
    for (let i = 0; i < nextSize; i++) {
      const key = nextKeys[i]!
      copy[key] = replaceEqualDeep(a[key], b[key])
      if (copy[key] === a[key] && a[key] !== undefined) equalItems++
    }
    return prevSize === nextSize && equalItems === prevSize ? prev : copy