Highlights

Glob-based configuration

Previously, it was not possible to use different ESLint configurations for two different files in the same directory. For example, projects that place test files in the same directory as the corresponding source files were unable to use different ESLint configurations for the test files. Adding support for this has been one of our most requested features.

This release adds support for glob-based configuration via an overrides key in a config file, which can be used to apply a configuration to specific globs. For example, you can now enable the mocha environment on only test files, with the following config:

module.exports = {
  rules: {
    // ... the rest of your config (applied to all files)
  },
  overrides: [
    {
      files: ["foo/**/*.spec.js", "bar/**/*.spec.js"],

      // Override config (only applied to files that match the given globs)
      env: { mocha: true }
    }
  ]
};

For full details, see the documentation.

Ignoring files from package.json

It’s common for users to use an .eslintignore file to indicate the files that they would like ESLint to ignore. However, if you don’t want to add additional files to your project root, you can now ignore files by setting the eslintIgnore property in a package.json file to a list of globs:

{
  "eslintIgnore": [
    "build/**/*.js",
    "dist/**/*.js"
  ]
}

Also see: documentation

Applying multiple autofixes simultaneously

When writing a custom rule that can automatically fix problems, one sometimes needs to apply multiple fixes atomically. For example, if an autofix adds parentheses around a piece of source code, adding only one parenthesis will result in a syntax error. Since ESLint does not guarantee that it will be able to apply every fix without conflicts, it was previously not possible to atomically apply multiple fixes (without using confusing workarounds).

Starting in 4.1.0, if you return an array of fixes from a fix function rather than a single fix, all the fixes in the array will be applied atomically.

context.report({
  node,
  message,
  fix(fixer) {
    return [
      fixer.insertTextBefore(node, "("),
      fixer.insertTextAfter(node, ")")
    ]
  }
})

Also see: Autofixing docs

Applying autofixes from Linter

When using ESLint’s Node.js API, it was previously not possible to get automatic fix information for a given source code and configuration when using eslint.Linter. Instead, one had to use eslint.CLIEngine, which is more general and less easy to use.

Starting in 4.1.0, you can now use Linter#verifyAndFix to get autofixing information when using Linter. (You should still use CLIEngine if you need to do more general operations, such as reading config files from the filesystem.)

For more details, see the documentation.

Other highlights

• An enforceForArrowConditionals option has been added to the no-extra-parens rule.
• An ignoreComments option has been added to the no-trailing-spaces rule.

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Full Changelog

Features

• a21dd32c New: Add overrides/files options for glob-based config (fixes #3611) (#8081) (Sylvan Mably)
• 5f81a68a New: Add eslintIgnore support to package.json (fixes #8458) (#8690) (Victor Hom)

Enhancements

• 291a7830 Update: enforceForArrowConditionals to no-extra-parens (fixes #6196) (#8439) (Evilebot Tnawi)
• 879688ce Update: Add ignoreComments option to no-trailing-spaces (#8061) (Jake Roussel)
• 98512881 Update: fix indent errors on multiline destructure (fixes #8729) (#8756) (Victor Hom)
• 673a58bc Update: support multiple fixes in a report (fixes #7348) (#8101) (Toru Nagashima)
• b5a70b4e Update: fix multiline binary operator/parentheses indentation (#8719) (Teddy Katz)
• ab8b0167 Update: fix MemberExpression indentation with “off” option (fixes #8721) (#8724) (Teddy Katz)
• eb5d12c1 Update: Add Fixer method to Linter API (#8631) (Gyandeep Singh)

Bug Fixes

• 7a1bc389 Fix: don’t pass default parserOptions to custom parsers (fixes #8744) (#8745) (Teddy Katz)
• b7cc1e6f Fix: Space-infix-ops should ignore type annotations in TypeScript (#8341) (Reyad Attiyat)
• 46e73eea Fix: eslint --init installs wrong dependencies of popular styles (fixes #7338) (#8713) (Toru Nagashima)

Documentation

• e8f1362a Docs: Remove wrong descriptions in padded-block rule (#8783) (Plusb Preco)
• 3608f06c Docs: Increase visibility of code of conduct (fixes #8758) (#8764) (Kai Cataldo)
• 3419f644 Docs: describe how to use formatters on the formatter demo page (#8754) (Teddy Katz)

Chores

• b58ae2e6 Chore: Only instantiate fileEntryCache when cache flage set (perf) (#8763) (Gyandeep Singh)
• c5b40528 Chore: enable computed-property-spacing on ESLint codebase (#8760) (Teddy Katz)
• a3ff8f21 Chore: combine tests in tests/lib/eslint.js and tests/lib/linter.js (#8746) (Teddy Katz)
• a82361b6 Chore: Prevent package-lock.json files from being created (fixes #8742) (#8747) (Teddy Katz)
• 26a2daab Chore: Cache fs reads in ignored-paths (fixes #8363) (#8706) (Victor Hom)