Allow you to call the default implementation of onErrorRetry

[robin-alphasophia]

Hello,

I would suggest allowing developers to call the default implementation of the onErrorRetry function.

Let me give you an example of why this is relevant:
In my next.js app, I try to fetch a user switch SWR in the top level _app.ts file. If there is an error 401 unauthorized, I know the user is not logged in - in that case, I do not need SWR to retry fetching the data but send the user to the login page. However, if the error is any other error, I want SWR to run the default exponential backoff.

Essentially, I suggest allowing something like this:

import useSWR, { onErrorRetry } from 'swr'

useSWR('/api/user', fetcher, {
  onErrorRetry: (error, key, config, revalidate, opts) => {

    if (error.status === 419) return;

    else onErrorRetry();
  }
})

Currently, I have solved it by coping the exponential backoff implementation from the SWR source code into my own source code, but now I am shipping twice the exact same code to our app users.

Best regards