Auth module not respecting dynamic router.base (Nuxt 2.15+)

[MrNaif2018]

Version

module: 5.0.0-1613647907.37b1156 (same with 4.x.x. series)
nuxt: 2.15.1

Nuxt configuration

mode:

• universal

Nuxt configuration

auth: {
    localStorage: false,
    cookie: {
      options: {
        expires: 7,
      },
    },
    strategies: {
      local: {
        endpoints: {
          login: {
            url: "/token",
            method: "post",
            propertyName: "access_token",
          },
          logout: false,
          user: { url: "/users/me", method: "get", propertyName: false },
        },
      },
    },
    plugins: ["~/plugins/auth.js"],
  },

plugins/auth.js

export default ({ $axios, $auth }) => {
  $axios.onError((error) => {
    if (
      error.response &&
      error.response.status === 401 &&
      !error.config.url.endsWith("/token")
    ) {
      $auth.logout()
    }
  })
}

Reproduction

Codesandbox seems to reject process.env, but basically, nuxt.config.js must have:

router: {
    base: process.env.ROOTPATH || "/",
  },

Then, run yarn build.
yarn start - all works as expected
ROOTPATH=/admin yarn start - by opening /admin, it redirects to /login and not to /admin/login.
Opening correct page manually all works.

Checklist

• I have tested with the latest Nuxt version and the issue still occurs
• I have tested with the latest module version and the issue still occurs
• I have searched the issue tracker and this issue hasn't been reported yet

What is expected?

A correct redirect to /admin/login to be done

What is actually happening?

Redirect to /login, ignoring router.base.
Note: it works if router.base is set statically (not via env var).
So maybe the module is not yet ready for nuxt/nuxt#8520

This second one is what I get after opening localhost:3000/admin:

If possible, could the fix be backported to the 4.x.x series?

[MrNaif2018]

Found a workaround (in auth plugin):

$auth.onRedirect((to, from) => {
    if (!process.server) return
    if (to.startsWith(decodeURI($config.app.basePath))) return to
    return urlJoin($config.app.basePath, to)
  })

[sogehige]

Found a workaround (in auth plugin):

$auth.onRedirect((to, from) => {
    if (!process.server) return
    if (to.startsWith(decodeURI($config.app.basePath))) return to
    return urlJoin($config.app.basePath, to)
  })

Doesn't seem working for home redirect. Any ideas?