ESLint v8.21.0 released

Highlights

• ESLint will now print deprecation warnings for two changes that are coming in ESLint v9: First, rules with options must specify schemas. Second, rules must be defined using the object-style format that has been available since ESLint v2 rather than the legacy function-style format. See RFC85 for full details.
• We took a big step toward ESLint’s new config system! The new FlatESLint class is now merged. Its API is not yet stable, and not all features are implemented yet, but it is accessible via the Node.js API for early testing. See RFC9 for the original design.

Features

• 7b43ea1 feat: Implement FlatESLint (#16149) (Nicholas C. Zakas)
• 92bf49a feat: improve the key width calculation in key-spacing rule (#16154) (Nitin Kumar)
• c461542 feat: add new allowLineSeparatedGroups option to the sort-keys rule (#16138) (Nitin Kumar)
• 1cdcbca feat: add deprecation warnings for legacy API in RuleTester (#16063) (Nitin Kumar)

Bug Fixes

• 0396775 fix: lines-around-comment apply allowBlockStart for switch statements (#16153) (Nitin Kumar)

Documentation

• 2aadc93 docs: add anchors to headings inside docs content (#16134) (Strek)

Chores

• 8892511 chore: Upgrade to Espree 9.3.3 (#16173) (Brandon Mills)
• 1233bee chore: switch to eslint-plugin-node’s maintained fork (#16150) (唯然)
• 97b95c0 chore: upgrade puppeteer v13 (#16151) (唯然)