biome

Ban Object.assign:

$fn($args) where {
    $fn <: Object.assign,
    register_diagnostic(
        span = $fn,
        message = "Prefer object spread instead of Object.assign()"
    )
}

CSS - enforce color classes:

language css;
$selector { $props } where {
    $props <: contains color: $color as $rule,
    not $selector <: r"\.color-.*",
    register_diagnostic(
        span = $rule,
        message = "Don't set explicit colors. Use .color-* classes instead."
    )
}

Plugin API

register_diagnostic() arguments:

Supported target languages: JavaScript (default) and CSS, plus JSON since v2.4 (the v2.4 release blog adds JSON; the linter/plugins/ reference page may still mention only JS/CSS - the blog is authoritative). Profile rule and plugin execution with biome lint --profile-rules ..

1. Use biome check as your single command - combines format, lint, and import organization 2. Start with recommended: true - disable individual rules as needed 3. Enable relevant domains - react, next, test, types based on your stack 4. Enable VCS integration - respects .gitignore, enables --changed/--staged 5. Use biome ci in pipelines - never writes files, clear exit codes 6. Pin exact versions - avoid surprise rule changes between releases 7. Run biome migrate --write after every upgrade 8. Use --staged in pre-commit hooks: biome check --staged --write --no-errors-on-unmatched . 9. Profile slow rules with biome lint --profile-rules (v2.4) 10. Use GritQL plugins for project-specific patterns instead of disabling rules globally