facebookexperimental/Recoil

useRecoilCallback batched set calls update state incorrectly

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#1935 opened on Aug 5, 2022

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 (14 comments) (0 reactions) (0 assignees)JavaScript (19,428 stars) (1,151 forks)batch import
bughelp wanted

Description

We've been using Recoil quite extensively and believe we have encountered a bug with useRecoilCallback and state updating.

There is a rootState atom that we want to update via a useRecoilCallback that contains multiple set calls. If the set calls within useRecoilCallback try to set the recoil state of rootState directly or through a single selector layer, the final rootState is as expected. However, if there is more than one layer of selector dependencies, it is only the last set that has a result on rootState.

Here is the CodeSandbox.

Expected: All steps change their state from ['1', '2', '3'] to ['one', 'two', 'three'] Result: The only step changing the state is the last one for which set has run. In effect: ['1', '2', '3'] changes to ['1', '2', 'three']

Contributor guide

Tech stack
javascripttypescriptreact
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
React basicsRecoil fundamentalsSelector dependencies
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Examine the implementation of useRecoilCallback in the Recoil source code, specifically how batched set calls are handled. Investigate how selector dependency layers affect state updates. Check if there are any existing tests or related issues that discuss transaction batching. Consider whether the issue is in the selector cache invalidation logic.