mushi-mushi/eslint: catch what AI tools leave behind

AI coding tools often ship two quiet bugs. A button looks finished, but its click does nothing. Or a page still shows the fake data the AI used while building it (John Doe, lorem ipsum). Nothing crashes, so no error tracker sees either one. Your users do.

mushi-mushi/eslint finds both while you build. ESLint (the tool that checks your code for mistakes as you type) runs these rules in your editor, in npm run lint and in CI.

Turn it on

You need mushi-mushi and ESLint 8 or newer in your project. Most apps made with Vite, Next.js or an AI builder have ESLint already. mushi-mushi does not install ESLint for you.

npm install mushi-mushi

Then add the recommended rules to your ESLint config:

import mushi from 'mushi-mushi/eslint'
 
export default [
  // …your other configs
  mushi.configs.recommended,
]

Prefer to ask your AI editor? Paste this:

Add the Mushi Mushi ESLint rules to this project: import mushi from
'mushi-mushi/eslint' in eslint.config.js and add mushi.configs.recommended to
the exported array. Then run the linter and fix what it reports.

Pick the rules yourself

import mushi from 'mushi-mushi/eslint'
 
export default [
  {
    plugins: { 'mushi-mushi': mushi },
    rules: {
      'mushi-mushi/no-dead-handler': 'error',
      'mushi-mushi/no-mock-leak': 'error',
    },
  },
]

recommended is also a named export: import { recommended } from 'mushi-mushi/eslint'. In a CommonJS config, use require('mushi-mushi/eslint').default.

Coming from eslint-plugin-mushi-mushi?

The rules moved into mushi-mushi/eslint. eslint-plugin-mushi-mushi is no longer published; its last version, 0.3.7, still installs. To switch, change the import to mushi-mushi/eslint. The rule names stay the same.

mushi-mushi/eslint works with flat config (eslint.config.js, the default since ESLint 9) only. An older .eslintrc loads plugins by package name, so it cannot load a subpath. Move to flat config to use it.

What the recommended rules catch

mushi.configs.recommended turns on three rules: no-dead-handler and no-mock-leak below, plus no-allowlist-jsx-textnode, which catches an allowlist comment written as JSX text (it would show up on the page).

The other 16 rules check the Mushi Mushi console’s own design system (tokens, <Card>, <PageHeaderBar>, page posture, the widget theme). They are in configs.internal and are not meant for other apps.

mushi-mushi/no-dead-handler: buttons that do nothing

Flags inline event handlers (on* props, and onClick / onSubmit-style object keys) whose body is empty, returns null, holds only console.* calls in a block, or throws “not implemented”, including inside useCallback. It checks inline functions only: a handler passed by name, such as onSubmit={noop}, is not followed. Files named *.test.*, *.spec.* and *.stories.* are skipped.

// ✗ caught
<button onClick={() => {}}>Submit</button>
<button onClick={() => { console.log('clicked') }}>Save</button>
 
// ✓ allowed
<button onClick={() => mutate()}>Submit</button>
<form onSubmit={handleSubmit}><button type="submit">Submit</button></form>
 
// ✓ allowed in tests + stories
<button onClick={() => {}} />        // foo.test.tsx, *.stories.tsx

mushi-mushi/no-mock-leak: fake data in real pages

Flags mock-library imports (@faker-js/faker, faker, msw, and similar), arrays of placeholder objects (John Doe, Jane Doe), and lorem ipsum or placeholder@example.com strings in production files. It skips files under a __tests__, test, tests, spec, stories, fixtures, mocks or __mocks__ folder, and files named *.test.*, *.spec.*, *.stories.* or *.mock.*.

// ✗ caught — apps/web/src/pages/Dashboard.tsx
const projects = [
  { name: 'John Doe', tasks: 12 },
  { name: 'Jane Doe', tasks: 7 },
]
 
// ✓ allowed — apps/web/src/__mocks__/projects.ts
export const projects = [
  { name: 'John Doe', tasks: 12 },
]

In CI

Run ESLint as its own step (for example npx eslint .) so a pull request fails when either rule reports. To record the findings in Mushi Mushi as well, write a JSON report (npx eslint -f json -o mushi-eslint.json src/) and pass it to the @mushi-mushi/mcp-ci gates command as eslint-report. That command does not run ESLint itself, and its dead_handler and mock_leak gates fail when no report is given.