immutable (beta): SWRGlobalState.get(cache) is undefined when using SSG

[hazae41]

Bug report

Description / Observed Behavior

I encounter this error on build when using useSWRImmutable on a Server-Side Generated page (getStaticProps)

const { data } = useSWRImmutable(key, fetcher)

TypeError: Cannot read property '0' of undefined

This code seems to be the cause:

https://github.com/vercel/swr/blob/master/src/use-swr.ts#L46

const [
  EVENT_REVALIDATORS,
  STATE_UPDATERS,
  MUTATION_TS,
  MUTATION_END_TS,
  CONCURRENT_PROMISES,
  CONCURRENT_PROMISES_TS
] = SWRGlobalState.get(cache) as GlobalState

SWRGlobalState.get(cache) seems to be undefined in this case

Additional Context

[email protected]

[huozhi]

@hazae41 Thanks for reporting and using the beta version of swr 🙏