nextjs - ✅(Solved) Fix TypeError: Converting circular structure to JSON after migration to Next 16 [1 pull requests, 16 comments, 8 participants]

jcubic · 2025-10-22T21:21:44Z

[nextjs] PR 85749: codemod fix: next-lint-to-eslint-cli did not handle 'next' plugin - Repository: vercel/next.js - Author: devjiwonchoi - State: closed | merg… # PR #85749: [codemod] fix: next-lint-to-eslint-cli did not handle `'next'` plugin - Repository: vercel/next.js - Author: devjiwonchoi - State: closed | merged: True - Link: https://github.com/vercel/next.js/pull/85749 ## Description (problem / solution / changelog) Codemod `next-lint-to-eslint-cli` did not handle `extends: ['next']` in legacy ESLint config. x-ref: https://github.com/vercel/next.js/issues/85244#issuecomment-3482558412 Fixes #85244 ## Changed files - `packages/next-codemod/transforms/__testfixtures__/next-lint-to-eslint-cli/legacy-config/.eslintrc.json` (modified, +2/-0) - `packages/next-codemod/transforms/__tests__/next-lint-to-eslint-cli.test.js` (modified, +13/-3) - `packages/next-codemod/transforms/next-lint-to-eslint-cli.ts` (modified, +46/-8) ## Fix / Workaround This can be fixed by create next 16 project and migrating the ESLint config. ### Link to the code that reproduces this issue https://github.com/jcubic/10xDevs/tree/eslint Sorry, this is not minimal reproduction but only relevant files are: * https://github.com/jcubic/10xDevs/blob/eslint/eslint.config.mjs * https://github.com/jcubic/10xDevs/blob/eslint/package.json The steps below create a new project that reproduce the error ### To Reproduce 1. Create new Next 15 project (with ESLint + TypeScript) 2. run `npx @next/codemod@latest upgrade latest` 3. run `npm install` 4. Run `npm lint` ### Current vs. Expected behavior * expect: no errors. * got: error `Converting circular structure to JSON` ### Provide environment information ```bash /bin/sh: line 1: yarn: command not found /bin/sh: line 1: pnpm: command not found Operating System: Platform: linux Arch: x64 Version: #1 SMP PREEMPT_DYNAMIC Sun Oct 12 16:31:16 UTC 2025 Available memory (MB): 31506 Available CPU cores: 20 Binaries: Node: 24.7.0 npm: 11.6.1 Yarn: N/A pnpm: N/A Relevant Packages: next: 16.0.0 // Latest available version is detected (16.0.0). eslint-config-next: N/A react: 19.2.0 react-dom: 19.2.0 typescript: 5.9.2 Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) Linting ### Which stage(s) are affected? (Select all that apply) npm run lint ### Additional context I'm not sure if this qualifies, but the codemod in documentation probably should update the ESLint file. This can be fixed by create next 16 project and migrating the ESLint config. This also turns out that this is a stacking error from ESLint. ESLint crash when trying to display the error: * https://github.com/eslint/eslint/issues/20237 If nothing can be done to fix the old setup, I would expect this information to be included in the migration instruction: * https://nextjs.org/docs/app/guides/upgrading/version-16

nextjs2025-10-22 21:21:44

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vercel/next.js#85244•Fetched 2026-04-08 02:16:49

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Error Message

The steps below create a new project that reproduce the error

got: error Converting circular structure to JSON This also turns out that this is a stacking error from ESLint. ESLint crash when trying to display the error:

Fix Action

Fix / Workaround

This can be fixed by create next 16 project and migrating the ESLint config.

PR fix notes

PR #85749: [codemod] fix: next-lint-to-eslint-cli did not handle `'next'` plugin

Repository: vercel/next.js
Author: devjiwonchoi
State: closed | merged: True
Link: https://github.com/vercel/next.js/pull/85749

Description (problem / solution / changelog)

Codemod next-lint-to-eslint-cli did not handle extends: ['next'] in legacy ESLint config.

x-ref: https://github.com/vercel/next.js/issues/85244#issuecomment-3482558412

Fixes #85244

Changed files

packages/next-codemod/transforms/__testfixtures__/next-lint-to-eslint-cli/legacy-config/.eslintrc.json (modified, +2/-0)
packages/next-codemod/transforms/__tests__/next-lint-to-eslint-cli.test.js (modified, +13/-3)
packages/next-codemod/transforms/next-lint-to-eslint-cli.ts (modified, +46/-8)

Code Example

/bin/sh: line 1: yarn: command not found
/bin/sh: line 1: pnpm: command not found

Operating System:
  Platform: linux
  Arch: x64
  Version: #1 SMP PREEMPT_DYNAMIC Sun Oct 12 16:31:16 UTC 2025
  Available memory (MB): 31506
  Available CPU cores: 20
Binaries:
  Node: 24.7.0
  npm: 11.6.1
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 16.0.0 // Latest available version is detected (16.0.0).
  eslint-config-next: N/A
  react: 19.2.0
  react-dom: 19.2.0
  typescript: 5.9.2
Next.js Config:
  output: N/A

RAW_BUFFERClick to expand / collapse

Link to the code that reproduces this issue

https://github.com/jcubic/10xDevs/tree/eslint

Sorry, this is not minimal reproduction but only relevant files are:

The steps below create a new project that reproduce the error

To Reproduce

Create new Next 15 project (with ESLint + TypeScript)
run npx @next/codemod@latest upgrade latest
run npm install
Run npm lint

Current vs. Expected behavior

expect: no errors.
got: error Converting circular structure to JSON

Provide environment information

/bin/sh: line 1: yarn: command not found
/bin/sh: line 1: pnpm: command not found

Operating System:
  Platform: linux
  Arch: x64
  Version: #1 SMP PREEMPT_DYNAMIC Sun Oct 12 16:31:16 UTC 2025
  Available memory (MB): 31506
  Available CPU cores: 20
Binaries:
  Node: 24.7.0
  npm: 11.6.1
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 16.0.0 // Latest available version is detected (16.0.0).
  eslint-config-next: N/A
  react: 19.2.0
  react-dom: 19.2.0
  typescript: 5.9.2
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Linting

Which stage(s) are affected? (Select all that apply)

npm run lint

Additional context

I'm not sure if this qualifies, but the codemod in documentation probably should update the ESLint file.

This can be fixed by create next 16 project and migrating the ESLint config.

This also turns out that this is a stacking error from ESLint. ESLint crash when trying to display the error:

https://github.com/eslint/eslint/issues/20237

If nothing can be done to fix the old setup, I would expect this information to be included in the migration instruction:

https://nextjs.org/docs/app/guides/upgrading/version-16

extent analysis

TL;DR

Create a new Next 16 project and migrate the ESLint configuration to resolve the "Converting circular structure to JSON" error.

Guidance

The error is likely caused by an incompatibility between the current ESLint configuration and the upgraded Next.js version.
To verify, try running npm lint with a minimal ESLint configuration to see if the error persists.
As a workaround, create a new Next 16 project and migrate the existing code to the new project, updating the ESLint configuration accordingly.
Consider updating the migration instructions to include information about potential ESLint configuration issues.

Example

No code snippet is provided as the issue is related to configuration and project setup.

Notes

The provided information suggests that the issue is specific to the ESLint configuration and the upgraded Next.js version. The solution may not apply to other versions or configurations.

Recommendation

Apply workaround: Create a new Next 16 project and migrate the ESLint configuration. This approach is recommended as it allows for a clean setup and avoids potential compatibility issues with the existing configuration.

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nextjs - ✅(Solved) Fix TypeError: Converting circular structure to JSON after migration to Next 16 [1 pull requests, 16 comments, 8 participants]

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Error Message

Fix Action

Fix / Workaround

PR fix notes

PR #85749: [codemod] fix: next-lint-to-eslint-cli did not handle `'next'` plugin

Description (problem / solution / changelog)

Changed files

Code Example

Link to the code that reproduces this issue

To Reproduce

Current vs. Expected behavior

Provide environment information

Which area(s) are affected? (Select all that apply)

Which stage(s) are affected? (Select all that apply)

Additional context

extent analysis

TL;DR

Guidance

Example

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Recommendation

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nextjs - ✅(Solved) Fix TypeError: Converting circular structure to JSON after migration to Next 16 [1 pull requests, 16 comments, 8 participants]

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Error Message

Fix Action

Fix / Workaround

PR fix notes

PR #85749: [codemod] fix: next-lint-to-eslint-cli did not handle 'next' plugin

Description (problem / solution / changelog)

Changed files

Code Example

Link to the code that reproduces this issue

To Reproduce

Current vs. Expected behavior

Provide environment information

Which area(s) are affected? (Select all that apply)

Which stage(s) are affected? (Select all that apply)

Additional context

extent analysis

TL;DR

Guidance

Example

Notes

Recommendation

Still need to ship something?

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TRENDING

PR #85749: [codemod] fix: next-lint-to-eslint-cli did not handle `'next'` plugin