Make element returned by useOutlet have stable-ish reference

[Malien]

I was trying to accomplish an exit animation for routes rendered in <Outlet />s. I need to hold onto the previous value of outlet until it finishes its animation.

const outlet = useOutlet()
const [heldOntoNode, setHeldOntoNode] = useState(outlet)

// If outlet changes to null, don't discard `heldOntoNode`.
// Otherwise, heldOntoNode should reflect the latest value of the outlet
if (outlet && heldOntoNode !== outlet) {
  // Calling setState in render body will discard the current render
  // and schedule a new one immediately
  setHeldOntoNode(outlet)
  return null
}

if (!heldOntoNode) return null

return (
  <Modal 
    // outlet set to null means we have to hide the modal
    // aka. trigger it's exit animation.
    open={!!outlet} 
    onExitAnimationEnd={() => setHeldOntoNode(null)}
  >
    {heldOntoNode}
  </Modal>
)

Calling setState in render is THE way to capture the previous value. Reading refs in render isn't really allowed.

Since useOutlet wraps the <RenderedRoute /> in <OutletContext.Provider />, the reference to the outer <OutletContext.Provider /> is always different on every re-render. And the code above triggers an infinite render loop.

This PR just wraps the resulting element in useMemo. That's it.

The workaround for me currently involves asserting that the element is in fact the react context, and grabbing the stable children prop.

I'm not sure we can guarantee stable references from useOutlet going forward, but that would be nice.

[changeset-bot]

🦋 Changeset detected

Latest commit: dab6471

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 11 packages

Name	Type
react-router	Patch
@react-router/architect	Patch
@react-router/cloudflare	Patch
@react-router/dev	Patch
react-router-dom	Patch
@react-router/express	Patch
@react-router/node	Patch
@react-router/serve	Patch
@react-router/fs-routes	Patch
@react-router/remix-routes-option-adapter	Patch
create-react-router	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[remix-cla-bot]

Hi @Malien,

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[remix-cla-bot]

Thank you for signing the Contributor License Agreement. Let's get this merged! 🥳

[brophdawg11]

Could you add a changeset for this?

[Malien]

@brophdawg11 Yeah. I did. Sorry for the late change

[github-actions]

🤖 Hello there,

We just published version 7.9.2-pre.0 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!

[github-actions]

🤖 Hello there,

We just published version 7.9.2 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!