Gitlab PKCE auth error on Decap 3.1

[kkellydesign]

As of the Decap 3.1 release on February 1, Gitlab PKCE is no longer working. I've tested both Firefox and Chrome.

When I visit /admin and try to log in, it immediately redirects me to Gitlab and shows the following screen:

To Reproduce
config.yml:

backend:
  name: gitlab
  repo: my_repo # Path to your GitHub repository
  auth_type: pkce
  branch: main
  app_id: my_id

admin/index.html – the link below causes the error. But changing the pinned version to 3.1.0-beta.2 fixes it.

   <script src="https://unpkg.com/[email protected]/dist/decap-cms.js"></script>

  <script src="/dist/js/nunjucks-slim.js"></script>
  <script src="/admin/util-bundled.js"></script>
  <script src="/admin/templates.js"></script>
  <script src="/admin/previews.js" type="text/babel"></script>

Applicable Versions:

• Decap CMS version: 3.1.1
• Git provider: Gitlab PKCE auth
• OS: mac locally.. but also on prod, with the CI running on Gitlab.

[blackb1rd]

I suspected #7014 break gitlab PKCE.

[demshy]

Closed by automation - please test and reopen if patch 3.1.2 does not fix this.
Thanks @blackb1rd