[CLIENT_FETCH_ERROR] with next-auth and v12.2.5-canary.4

[awareness481]

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 20.6.0: Tue Feb 22 21:10:42 PST 2022; root:xnu-7195.141.26~1/RELEASE_ARM64_T8101
Binaries:
  Node: 16.15.1
  npm: 8.11.0
  Yarn: N/A
  pnpm: 7.6.0
Relevant packages:
  next: 12.2.5-canary.4
  eslint-config-next: N/A
  react: 18.2.0
  react-dom: 18.2.0

What browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

No response

Describe the Bug

When trying to login, an error appears. Not happening in earlier canary versions. (can only repro in v12.2.5-canary.4)

{
    "error": {
        "message": "Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
        "stack": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
        "name": "SyntaxError"
    },
    "url": "/api/auth/session",
    "message": "Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "client": true
}

ref: nextauthjs/next-auth#5008 (comment)

Expected Behavior

To be able to login

Link to reproduction

https://github.com/awareness481/next-auth-v12.2.5-canary.4

To Reproduce

1. Clone https://github.com/awareness481/next-auth-v12.2.5-canary.4 (next-auth example with canary version)
2. Install deps
3. Try to login
4. Observe error

(Edit: If you dont have at least one provider setup, you ll get a different error message but it is irrelevant)

[awareness481]

Update

I can confirm that this is the PR that is causing the issues #38483 (although weirdly enough, it seems to work for most envs)

To confirm this I:

1. Setup a local next.js, with the latest version (v12.2.5-canary.4)
2. Run git revert -m 1 4e6d05575ee6c0c4f78130519f1d3f198bc05084 (reverts above PR)
3. Setup my repro repo to work with the local next.js
4. Setup google envs and provider & was able to log in

[ijjk]

Hi, thanks for the detailed info, this should be fixed in v12.2.5-canary.5, please update and give it a try!

[github-actions]

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