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nextjs - ✅(Solved) Fix Bug: ESLint Not Triggering Realtime Errors in Next.js 15.5.6 [1 pull requests, 6 comments, 3 participants]

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vercel/next.js#86449•Fetched 2026-04-08 02:10:57
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ESLint fails to show real-time errors and warnings in VSCode editor when working with Next.js 15.5.6 components, even when code clearly violates linting rules. Additionally, Next.js build process incorrectly reports ESLint as not installed or undetectable when using flat ESLint config with pnpm.

Error Message

  1. Build failures with misleading error messages about ESLint not being installed
  • Build fails with false "ESLint not installed" error // ⚠️ Expected: ESLint should warn that x is unused. // ❌ Actual: No lint error or warning appears in the editor.

Root Cause

ESLint fails to show real-time errors and warnings in VSCode editor when working with Next.js 15.5.6 components, even when code clearly violates linting rules. Additionally, Next.js build process incorrectly reports ESLint as not installed or undetectable when using flat ESLint config with pnpm.

Fix Action

Fix / Workaround

Additional Context

  • Reproducible in fresh projects
  • Started after Next.js 15.5.x upgrade
  • Not fixed by clearing cache
  • Affects both macOS and Windows

PR fix notes

PR #86469: Fix: Improve ESLint realtime detection for IDE integration (Issue #86…

Description (problem / solution / changelog)

…449)

Enhanced ESLint configuration to improve realtime error detection in IDEs (Issue #86449)

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Changed files

  • eslint.config.mjs (modified, +1/-0)
RAW_BUFFERClick to expand / collapse

Description

ESLint fails to show real-time errors and warnings in VSCode editor when working with Next.js 15.5.6 components, even when code clearly violates linting rules. Additionally, Next.js build process incorrectly reports ESLint as not installed or undetectable when using flat ESLint config with pnpm.

Reproduction Link

https://github.com/jsdev-robin/munza-client/blob/v-0.1.4/apps/admin/src/app/page.tsx

Current Behavior

  1. No real-time ESLint feedback in VSCode editor for obvious violations (e.g., unused variables)
  2. Build failures with misleading error messages about ESLint not being installed
  3. Inconsistent ESLint detection between development and production builds

Expected Behavior

  1. ✅ ESLint should show real-time errors and warnings in VSCode
  2. ✅ Next.js should correctly detect ESLint when installed via pnpm
  3. ✅ Build should only fail on actual ESLint errors, not configuration issues
  4. ✅ Clear documentation for flat ESLint config with Next.js 15+

Current Behavior

  • No real-time ESLint warnings in editor
  • Build fails with false "ESLint not installed" error
  • ESLint rules not enforced during development

Expected Behavior

  • Real-time ESLint errors in VSCode
  • Build only fails on actual lint errors
  • Proper ESLint detection with pnpm

Environment

  • Next.js: 15.5.6
  • Node.js: 20.x
  • Package Manager: pnpm
  • OS: Windows 10

Affected Areas

  • next build
  • ESLint integration
  • Development server linting

Additional Context

  • Reproducible in fresh projects
  • Started after Next.js 15.5.x upgrade
  • Not fixed by clearing cache
  • Affects both macOS and Windows

Code Example

const page = () => {
  const x = 'I am X';

  // ⚠️ Expected: ESLint should warn that `x` is unused.
  // ❌ Actual: No lint error or warning appears in the editor.

  return <div>page</div>;
};

export default page;

extent analysis

TL;DR

Check the ESLint configuration and ensure that it is properly integrated with the Next.js project, as the issue might be related to the flat ESLint config and pnpm usage.

Guidance

  • Verify that the .eslintrc file is correctly configured and that the eslint package is installed as a dev dependency using pnpm.
  • Check the VSCode settings to ensure that the ESLint extension is enabled and configured to use the project's ESLint configuration.
  • Try running pnpm run lint to see if ESLint works correctly from the command line, which can help determine if the issue is specific to the VSCode integration.
  • Review the Next.js documentation for any specific requirements or recommendations for using ESLint with pnpm.

Example

No specific code example is provided, as the issue seems to be related to the configuration and setup of ESLint with Next.js and pnpm.

Notes

The issue might be related to the upgrade to Next.js 15.5.x, and it's worth checking the release notes and documentation for any changes that could affect ESLint integration.

Recommendation

Apply workaround by checking and adjusting the ESLint configuration and VSCode settings to ensure proper integration with the Next.js project, as the issue seems to be related to the configuration and setup rather than a specific version issue.

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