Guard/check missing in areHooksInputEqual()?

[tomkelsey]

Hi,

I've noticed some server logs with the following error:

TypeError: Cannot read properties of undefined (reading 'length')
at areHookInputsEqual (/var/app/current/node_modules/react-ssr-prepass/dist/react-ssr-prepass.js:295:29)
at Object.useMemo (/var/app/current/node_modules/react-ssr-prepass/dist/react-ssr-prepass.js:301:6)

Looking at the function, it appears there's no guard/check that prevDeps may be undefined?

function areHookInputsEqual(
  nextDeps: Array<mixed>,
  prevDeps: Array<mixed> | null
) {
  // NOTE: The warnings that are used in ReactPartialRendererHooks are obsolete
  // in a prepass, since these issues will be caught by a subsequent renderer anyway
  if (prevDeps === null) return false

  for (let i = 0; i < prevDeps.length && i < nextDeps.length; i++) {
    if (!is(nextDeps[i], prevDeps[i])) return false
  }

  return true
}

I just wanted to highlight it as a potential issue. I'm not sure if it's implementation problem my end that's causing prevDeps to be undefined (rather than null)?

But just in case - in normal use - prevDeps can be undefined perhaps there should be a guard/check in place to protect against this? Could the check just be if (!prevDeps) return false instead?