PassportJS OAuth2Strategy: authenticate returns 400 instead of redirecting - express

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.