Bug: Error while loading rule '@stylistic/indent': Cannot read properties of undefined (reading 'length')

[pkuczynski]

Environment

ESLint version: 9.12.0
@eslint/markdown version: 6.2.0
Node version: 20.12.2
npm version: 10.8.3
Operating System: macOS 15.0.1

Which language are you using?

gfm

What did you do?

Configuration

import js from '@eslint/js'
import stylistic from '@stylistic/eslint-plugin'
import markdown from '@eslint/markdown'
import ts from 'typescript-eslint'

export default ts.config(
  // general linter settings
  {
    linterOptions: {
      reportUnusedDisableDirectives: 'error'
    }
  },

  // stylistic and formatting
  stylistic.configs.customize({
    braceStyle: '1tbs',
    commaDangle: 'never',
    jsx: false
  }),
  {
    rules: {
      '@stylistic/arrow-parens': ['error', 'as-needed', { requireForBlockBody: true }],
      '@stylistic/no-multiple-empty-lines': ['error', { max: 1, maxEOF: 0, maxBOF: 0 }],
      '@stylistic/object-curly-newline': ['error', {
        ObjectExpression: { multiline: true, consistent: true },
        ObjectPattern: { multiline: true, consistent: true },
        ImportDeclaration: 'never',
        ExportDeclaration: { multiline: true, consistent: true, minProperties: 2 }
      }]
    }
  },

  // typescript
  {
    name: 'typescript',
    files: ['**/*.ts'],
    extends: [
      ...ts.configs.strictTypeChecked,
      ...ts.configs.stylisticTypeChecked
    ]
  },

  // markdown code-blocks
  ...markdown.configs.recommended,
)

My README looks roughly like this:

# My application

## Run application

```bash
npm start
```

## Test

```bash
npm run test
```

What did you expect to happen?

It would work

What actually happened?

I am getting an error:

TypeError: Error while loading rule '@stylistic/indent': Cannot read properties of undefined (reading 'length')
Occurred while linting /xyz/README.md
    at new TokenInfo (/xyz/node_modules/@stylistic/eslint-plugin/dist/rules/indent.js:148:32)
    at create (/xyz/node_modules/@stylistic/eslint-plugin/dist/rules/indent.js:573:23)
    at Object.create (/xyz/node_modules/@stylistic/eslint-plugin/dist/utils.js:474:14)
    at create (/xyz/node_modules/@stylistic/eslint-plugin/dist/rules/indent.js:1383:28)
    at Object.create (/xyz/node_modules/@stylistic/eslint-plugin/dist/utils.js:474:14)
    at createRuleListeners (/xyz/node_modules/eslint/lib/linter/linter.js:943:21)
    at /xyz/node_modules/eslint/lib/linter/linter.js:1068:84
    at Array.forEach (<anonymous>)
    at runRules (/xyz/node_modules/eslint/lib/linter/linter.js:999:34)
    at #flatVerifyWithoutProcessors (/xyz/node_modules/eslint/lib/linter/linter.js:1914:31)

Link to Minimal Reproducible Example

https://stackblitz.com/edit/stackblitz-starters-tu4l2x?file=eslint.config.mjs&view=editor

Participation

• I am willing to submit a pull request for this issue.

Additional comments

No response

[pkuczynski]

Added example on stackblitz...

[nzakas]

@stylistic/indent is a JavaScript rule but you're trying to run it on a Markdown file. The problem is that stylistic.configs.customize() is returning a config that doesn't have a files key, so it's being applied to all files, including Markdown files. You'll need to add a files key. See https://eslint.org/docs/latest/use/configure/combine-configs#apply-a-config-array-to-a-subset-of-files

Note: You can also use --inspect-config to be able to see which configs are being applied to a particular file. That's a good way to debug problems like this.

[pkuczynski]

Thank you for reply @nzakas. I followed your suggestion and changed my config like this: https://stackblitz.com/edit/stackblitz-starters-jf9eon?file=eslint.config.mjs

  // stylistic and formatting
  {
    ...stylisticConfig,
    files: ['**/*.ts', '**/*.js'],
    rules: {
      ...stylisticConfig.rules,
      '@stylistic/arrow-parens': [
        'error',
        'as-needed',
        { requireForBlockBody: true },
      ],
      // ...
  }

where

const stylisticConfig = stylistic.configs.customize({
  braceStyle: '1tbs',
  commaDangle: 'never',
  jsx: false,
})

But this time it started to throw new error:

TypeError: sourceCode.getScope is not a function
    at Object.create (file:///home/projects/stackblitz-starters-mbx7ch/node_modules/eslint/lib/rules/logical-assignment-operators.js#cjs:233:37)
    at createRuleListeners (file:///home/projects/stackblitz-starters-mbx7ch/node_modules/eslint/lib/linter/linter.js#cjs:943:21)
    at eval (file:///home/projects/stackblitz-starters-mbx7ch/node_modules/eslint/lib/linter/linter.js#cjs:1068:84)
    at Array.forEach (<anonymous>)
    at runRules (file:///home/projects/stackblitz-starters-mbx7ch/node_modules/eslint/lib/linter/linter.js#cjs:999:34)
    at #flatVerifyWithoutProcessors (file:///home/projects/stackblitz-starters-mbx7ch/node_modules/eslint/lib/linter/linter.js#cjs:1911:31)
    at Linter._verifyWithFlatConfigArrayAndWithoutProcessors (file:///home/projects/stackblitz-starters-mbx7ch/node_modules/eslint/lib/linter/linter.js#cjs:1992:49)
    at Linter._verifyWithFlatConfigArray (file:///home/projects/stackblitz-starters-mbx7ch/node_modules/eslint/lib/linter/linter.js#cjs:2081:21)
    at Linter.verify (file:///home/projects/stackblitz-starters-mbx7ch/node_modules/eslint/lib/linter/linter.js#cjs:1528:61)
    at Linter.verifyAndFix (file:///home/projects/stackblitz-starters-mbx7ch/node_modules/eslint/lib/linter/linter.js#cjs:2319:29)

It goes away if I comment off markdown at the bottom of the config.

PS: I am not able to reopen this issue, so maybe you could? Thanks...

[nzakas]

It's the same problem - you're running JS rules on Markdown files. Use --inspect-config to figure out which rules are being applied to your Markdown files.