ESLint v9.0.0-alpha.2 released

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@9.0.0-alpha.2 --save-dev

Migration Guide

As there are a lot of changes, we’ve created a migration guide describing the breaking changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

no-restricted-imports configuration improvements

In v8.x, if multiple entries in the paths array of your configuration for the no-restricted-imports rule had the same name property, only the last one would apply. In v9.0.0, all entries apply, allowing for specifying different error messages for different imported names.

RuleTester checks for duplicate tests

As of v9.0.0, RuleTester detects and reports duplicate test cases.

Breaking Changes

• 57089cb feat!: no-restricted-imports allow multiple config entries for same path (#18021) (Milos Djermanovic)
• 2e1d549 feat!: detect duplicate test cases (#17955) (Bryan Mishkin)

Features

• 26093c7 feat: fix false negatives in no-this-before-super (#17762) (Yosuke Ota)
• 5471e43 feat: convert unsafe autofixes to suggestions in no-implicit-coercion (#17985) (Gürgün Dayıoğlu)
• e3051be feat: emit warning when .eslintignore file is detected (#17952) (Nitin Kumar)

Bug Fixes

• 39076fb fix: handle absolute file paths in RuleTester (#17989) (Nitin Kumar)

Documentation

• 33d1ab0 docs: add more examples to flat config ignores docs (#18020) (Milos Djermanovic)
• e6eebca docs: Update sort-keys options properties count (#18025) (LB (Ben Johnston))
• 1fedfd2 docs: Improve flat config ignores docs (#17997) (Nicholas C. Zakas)
• 38b9b06 docs: update valid-typeof rule (#18001) (Tanuj Kanti)
• b4abfea docs: Update note about ECMAScript support (#17991) (Francesco Trotta)
• 6788873 docs: Update release blog post template (#17994) (Nicholas C. Zakas)
• 1f37442 docs: Add sections on non-npm plugin configuration (#17984) (Nicholas C. Zakas)

Chores

• 6ffdcbb chore: upgrade @eslint/js@9.0.0-alpha.2 (#18038) (Milos Djermanovic)
• 2c12715 chore: package.json update for @eslint/js release (Jenkins)
• cc74c4d chore: upgrade espree@10.0.0 (#18037) (Milos Djermanovic)
• dfb68b6 chore: use Node.js 20 for docs sites (#18026) (Milos Djermanovic)
• 8c1b8dd test: add more tests for ignoring files and directories (#18018) (Milos Djermanovic)
• 60b966b chore: update dependency @eslint/js to v9.0.0-alpha.1 (#18014) (renovate[bot])
• c893bc0 chore: update markdownlint to v0.33.0 (#17995) (Nitin Kumar)