biome-plugin-prefer-arrow-function

Biome GritQL plugin that reports function declarations and suggests using arrow functions instead.

Biome's built-in useArrowFunction rule only converts function expressions (const foo = function() {}). This plugin covers the gap by detecting function declarations (function foo() {}).

Requires Biome v2.0+

Detected patterns

function foo() {}                   // plain declaration
function foo(a, b) { return a + b } // with params
export function foo() {}            // named export
export default function foo() {}    // default export
async function foo() {}             // async

Excluded patterns

function* gen() {}          // generator — no arrow equivalent
export function* gen() {}   // exported generator

Usage

In this repo (for testing)

npm install
npx @biomejs/biome lint __tests__/

In another project

Point to the .grit file from your biome.json:

{
  "plugins": [
    // relative or absolute path to the .grit file
    "../biome-plugin-prefer-arrow-function/prefer-arrow-function.grit"
  ]
}

Then run biome lint as usual.

Limitations

• GritQL plugins currently support diagnostics only — no auto-fix.
• Generator functions (function*) are naturally excluded because the pattern doesn't match the * syntax.

References

• biomejs/biome#7108 — original feature request
• Biome Linter Plugins docs
• GritQL reference