ESLint v9.39.0 released

Highlights

More precise problem locations

ESLint v9.39.0 introduces improvements that narrow the highlighted locations for certain rule violations. By reducing unnecessary highlighting, these changes cut down on visual noise and make issues in code easier to spot and fix.

Here’s what’s new:

• complexity: In v9.38.0, this rule was updated to highlight only a function’s header instead of the entire function. With v9.39.0, the same refinement now applies to class static blocks: only the header is highlighted, not the whole block.
• for-direction: Now highlights only the header portion of a for loop, instead of the full statement.
• no-dupe-args: Now highlights just the argument list in a function definition, not the whole function.
• no-dupe-class-members: Now highlights only the identifiers of duplicated members, rather than their full definitions.

Unified rule performance report

When the TIMING environment variable is set and ESLint runs in multithread mode with the --concurrency option, the output now includes a single, unified performance report. This consolidated report aggregates timing data from all threads, replacing the previous behavior of printing multiple separate reports.

Example:

$ TIMING=1 npx eslint --concurrency=2
Rule                                | Time (ms) | Relative
:-----------------------------------|----------:|--------:
jsdoc/valid-types                   |   484.199 |     5.1%
n/no-extraneous-require             |   431.187 |     4.5%
jsdoc/check-access                  |   375.205 |     3.9%
jsdoc/check-values                  |   323.224 |     3.4%
jsdoc/check-types                   |   308.546 |     3.2%
jsdoc/check-tag-names               |   305.308 |     3.2%
n/no-unsupported-features/es-syntax |   275.097 |     2.9%
expect-type/expect                  |   257.434 |     2.7%
jsdoc/check-alignment               |   255.678 |     2.7%
jsdoc/require-property-type         |   250.951 |     2.6%
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Features

• cc57d87 feat: update error loc to key in no-dupe-class-members (#20259) (Tanuj Kanti)
• 126552f feat: update error location in for-direction and no-dupe-args (#20258) (Tanuj Kanti)
• 167d097 feat: update complexity rule to highlight only static block header (#20245) (jaymarvelz)

Bug Fixes

• 15f5c7c fix: forward traversal step.args to visitors (#20253) (jaymarvelz)
• 5a1a534 fix: allow JSDoc comments in object-shorthand rule (#20167) (Nitin Kumar)
• e86b813 fix: Use more types from @eslint/core (#20257) (Nicholas C. Zakas)
• 927272d fix: correct Scope typings (#20198) (jaymarvelz)
• 37f76d9 fix: use AST.Program type for Program node (#20244) (Francesco Trotta)
• ae07f0b fix: unify timing report for concurrent linting (#20188) (jaymarvelz)
• b165d47 fix: correct Rule typings (#20199) (jaymarvelz)
• fb97cda fix: improve error message for missing fix function in suggestions (#20218) (jaymarvelz)

Documentation

• d3e81e3 docs: Always recommend to include a files property (#20158) (Percy Ma)
• 0f0385f docs: use consistent naming recommendation (#20250) (Alex M. Spieslechner)
• a3b1456 docs: Update README (GitHub Actions Bot)
• cf5f2dd docs: fix correct tag of no-useless-constructor (#20255) (Tanuj Kanti)
• 10b995c docs: add TS options and examples for nofunc in no-use-before-define (#20249) (Tanuj Kanti)
• 2584187 docs: remove repetitive word in comment (#20242) (reddaisyy)
• 637216b docs: update CLI flags migration instructions (#20238) (jaymarvelz)
• e7cda3b docs: Update README (GitHub Actions Bot)
• 7b9446f docs: handle empty flags sections on the feature flags page (#20222) (sethamus)

Chores

• dfe3c1b chore: update @eslint/js version to 9.39.0 (#20270) (Francesco Trotta)
• 2375a6d chore: package.json update for @eslint/js release (Jenkins)
• a1f4e52 chore: update @eslint dependencies (#20265) (Francesco Trotta)
• c7d3229 chore: update dependency @eslint/core to ^0.17.0 (#20256) (renovate[bot])
• 27549bc chore: update fuzz testing to not error if code sample minimizer fails (#20252) (Milos Djermanovic)
• a1370ee ci: bump actions/setup-node from 5 to 6 (#20230) (dependabot[bot])
• 9e7fad4 chore: add script to auto-generate eslint:recommended configuration (#20208) (唯然)