Extend GitLab provider to handle both self-hosted instances and additional scopes

[db6edr]

Description 📓

The current implementation of the GitLab provider only works with the managed instance at https://gitlab.com and the scope read_user; see line

next-auth/packages/core/src/providers/gitlab.ts

Line 100 in 039a14d

authorization: "https://gitlab.com/oauth/authorize?scope=read_user",

and following.

To make the provider work with a self-hosted instance, one needs to find the three options that need to be replaced and their respective values.

Similar when needing additional scopes; for those it's only one option that needs to be changed, but it must be found as well.

I suggest to extend the provider function with additional parameters

• gitlabInstance that defaults to https://gitlab.com/ when omitted or falsy and
• scopes that defaults to read_user

Any recommendations, suggestions, questions? If not, I'd start a PR.

How to reproduce ☕️

Proposed implementation:

export default function GitLab<P extends GitLabProfile>(
  options: OAuthUserConfig<P>,
  gitlabInstance = "https://gitlab.com/",
  scopes: string|string[] = "read_user"
): OAuthConfig<P> {
  if (!gitlabInstance.endsWith("/")) {
    gitlabInstance = gitlabInstance + "/";
  }

  scopes = Array.isArray(scopes) ? scopes.join("+") : scopes.replace(" ", "+");

  authorization: `${gitlabInstance}oauth/authorize?scope=${scopes}`;
  token: `${gitlabInstance}oauth/token`;
  userinfo: `${gitlabInstance}api/v4/user`;
...

Contributing 🙌🏽

Yes, I am willing to help implement this feature in a PR

[rohan-chaturvedi]

It seems this is already supported, simply by providing your gitlab instance host in authorization.url as well as token and userInfo in the provider settings. We were able to easily add support for self-hosted gitlab to our app by supplying these values: https://github.com/phasehq/console/pull/259/files#diff-72917a6d5e6f09a7fd63d62c78d8117fc723f0d5409411cfde0d14a5bbda5842