PassportJS OAuth2Strategy: authenticate returns 400 instead of redirecting

Question

I'm trying to setup discord oauth2 pkce using passportjs and the passport-oauth2

const discordStrategy = new OAuth2Strategy({
  authorizationURL: 'https://discord.com/api/oauth2/authorize',
  tokenURL: 'https://discord.com/api/oauth2/token',
  clientID: DISCORD_CLIENT_ID,
  clientSecret: DISCORD_CLIENT_SECRET,
  callbackURL: DISCORD_CALLBACK_URL,
  state: true,
  pkce: true,
  scope: ['identity', 'scope'],
  passReqToCallback: true,
},
  (req: Request, accessToken: string, refreshToken: string, profile: DiscordUserProfile, cb: any) => {
    prisma.user.findUnique({ where: { email: profile.email ?? '' }}).then(foundUser => {
      if (foundUser === null) {
        // Create a new user with oauth identity.
      } else {
        cb(null, foundUser)
      }
    }).catch(error => {
      cb(error, null);
    })
  });

I've been following the google example as well as some others, these examples indicate that, I should be able to use:

passport.use('discord', discordStrategy);

and

authRouter.get('/discord', passport.authenticate('discord'));

and this should redirect to the OAuth2 providers login page, but instead, I get a 400 Bad Request "The request cannot be fulfilled due to bad syntax." The response body contains an object:

{"scope": ["0"]}

Why is this happening instead of the expected redirect?

My intention is that, once the user logs in, I should get a code, then I can post that code and the code verifier to get an access token, then once the access token is obtained, the actual authenticate call can be made

Edit: I put breakpoints in the passport.authenticate function and I stepped through it. It does actually get through everything and it calls the redirect. The parsed URL it generates, even if I copy it and manually navigate to the URL, it gives me the same, just gives:

{"scope": ["0"]}

and no login page, why?

Answer 1

If you add a version number to the base api url, e.g. /v9 it gives a full error message.

It turned out I had typo'd the scopes, I had 'identity' instead of 'identify' - now this part of the process is working as expected.