Should Jotai support atom graph cycles?

[dmaskasky]

const a = atom((get) => {
  return get(b)
})
const b = atom((get) => {
  return get(a)
})

A more real world example would be:

const valueAtom = atom(0)
const effectAtom = atomEffect((get) => {
  console.log('derived is now', get(derivedAtom))
})
const derivedAtom = atom((get) => {
  get(effectAtom) // mount effect
  return get(valueAtom)
})

[dai-shi]

I don't think we should support it. It's mathematically wrong, or undefined, right?
I think the cycles would cause infinite loops, or should error with cycle / infinite loop detection.

I think it's reasonable for atomEffect to have its own workaround as effect can be imperative instead of declarative.

[na2hiro]

I tested with withAtomEffect in this sandbox https://stackblitz.com/edit/react-ts-m9mskdnu?file=index.tsx

• Atom effects are not set up when used with useHydrateAtoms(). Isn't it a bug?
• If set up like as you provided initially (See 2, WithoutHydration), the effect runs initially but doesn't run for the succeeding updates. If I update the code to get() is passed the return value of withAtomEffect, it works as expected (See 3, WithoutHydration). It seems that the first arg of withAtomEffect() should be always inlined to avoid this pitfall. I wonder if this sounds true

[dmaskasky]

Confirmed. Reproduction: https://stackblitz.com/edit/react-ts-euct7mig?file=index.tsx

I added these two issues:

• withAtomEffect does not call effect function when used by useHydration jotaijs/jotai-effect#46
• withAtomEffect does not call effect function when listening to target atom jotaijs/jotai-effect#47

[na2hiro]

@dmaskasky Thanks!

[dmaskasky]

@na2hiro Both issues are now resolved. Thank you for bringing this to my attention!
Please upgrade to v1.0.6. Release notes

[na2hiro]

Great, I could hook up the effects the way I wanted now. Thanks a lot for the quick resolution!