_app context loses state when navigating back (looks like vercel only, 10.0.2^18)

[wiesson]

Bug report

Describe the bug

I have wrapped a context around _app and it looses it's state when I navigate back (via browser or <Link /> (at least I think that is the problem, might be introduced with #19006, but I'm also not 100% sure)

_app.js

import { ListContextProvider } from "../context";

function MyApp({ Component, pageProps }) {
  return (
    <ListContextProvider>
      <Component {...pageProps} />
    </ListContextProvider>
  );
}

Usage in List Component

const List = ({ items = [] }) => { // initial state comes from the parent component
  const context = useContext(ListContext);

  function loadMoreFn() {
    context.addFn([makeId(6), makeId(6), makeId(6), makeId(6)]); // just faking additional random data 
  }

  return (
    <>
      <div className={styles.grid}>
        {items.concat(context.items).map((item) => ( // yes, could also be done with useEffect and useState, but for simplicity 
          <Link href={`/detail/${item}`} key={item}>
            <a className={styles.card}>
              <h3>{item} &rarr;</h3>
            </a>
          </Link>
        ))}
      </div>

      <button onClick={loadMoreFn}>Load more</button>
    </>
  );
};

To Reproduce

Repo - https://github.com/wiesson/next-testing
Basic demo - https://next-testing-six.vercel.app

1. Click on load more,
2. Follow an item (loaded or existing)
3. go back afterwards

Expected behavior

The state should not be cleared and it worked well before 10.0.2. It does not happen locally (next start), but on Vercel.

Screenshots

If applicable, add screenshots to help explain your problem.

System information

• Version of Next.js: 10.0.2^18
• Deployment: Vercel

[ijjk]

HI, this should be corrected from the above PR now, please re-deploy your application and give it a try!

[wiesson]

HI, this should be corrected from the above PR now, please re-deploy your application and give it a try!

Looks good!! Thank you very much! 🙌

[balazsorban44]

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