fix: onMount setSelf does not notify listeners

[dmaskasky]

Related Bug Reports or Discussions

• onMount setSelf does not notify listeners #2810

onMount setSelf does not notify listeners (#2810)

• adds failing test: when changing the atom value with onMount setSelf, subscribers are not called
• fixes failing test

Why aren't listeners called when calling setAtom in onMount?

Because the listener is added only after flushPending is called.

Fix: swap the order of flush pending and listeners.add(listener).

Why aren't listeners called when calling setAtom in onUnmount?

Because the listener is deleted before flushPending is called.

There's a logic cycle here:

1. the listener is deleted before calling unmountAtom, because unmountAtom only processes if atomState.m.l.size === 0
2. unmountAtom adds the onUnmount pending function
3. flushPending calls onUnmount pending function
4. setAtom fires in onUnmount pending function, which updates the atom
5. subscriber doesn't fire because it was removed in 1

👉 NOTE: This is expected behavior.

Check List

• pnpm run prettier for formatting code and docs

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
jotai	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 14, 2024 6:42pm

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

[github-actions]

Preview in LiveCodes

Latest commit: 371a9bf
Last updated: Nov 14, 2024 6:42pm (UTC)

Playground	Link
React demo	https://livecodes.io?x=id/3Q267UNQN

---

See documentations for usage instructions.