2nd/10_Wiki/Topics/Frontend/ESLint-Plugin-Development.md

---
id: wiki-2026-0508-eslint-plugin-development
title: ESLint Plugin Development
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [ESLint Custom Rules, ESLint Plugin Authoring]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [eslint, plugin, ast, linting]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: JavaScript/TypeScript
  framework: ESLint 9
---

# ESLint Plugin Development

## 매 한 줄
> **"매 ESLint plugin은 AST visitor + RuleTester."**. ESLint 9 (2024-) Flat config 시대에는 plugin = `{rules, configs, processors}` object 의 export. 매 rule = `meta` (docs, fixable, schema) + `create(context)` returning visitor map (e.g., `CallExpression(node) { ... }`).

## 매 핵심

### 매 AST 기반
- ESLint = ESTree spec (espree parser default; @typescript-eslint/parser for TS).
- 매 rule visitor가 specific node type 방문 — `Identifier`, `CallExpression`, `JSXElement` 등.
- `context.report({node, message, fix})` 으로 violation 보고.

### 매 Plugin shape (Flat config)
- ESLint 9+ deprecated `.eslintrc` 형식 — 매 `eslint.config.js` flat config.
- Plugin export = `{meta, rules, configs, processors}` — meta에 `name/version` 명시.

### 매 응용
1. Internal style guide — 매 monorepo 의 component naming, import order.
2. Framework rules — `eslint-plugin-react`, `eslint-plugin-vue` 처럼 framework-specific.
3. Security lint — 매 dangerous API (eval, innerHTML) 금지.
4. Migration codemod — 매 deprecated API 의 자동 fixer.

## 💻 패턴

### 1. Minimal rule skeleton
```javascript
// rules/no-foo.js
export default {
  meta: {
    type: 'problem',
    docs: { description: 'disallow Foo identifier', recommended: true },
    fixable: 'code',
    schema: [],
    messages: { unexpected: "'{{name}}' is not allowed." },
  },
  create(context) {
    return {
      Identifier(node) {
        if (node.name === 'Foo') {
          context.report({
            node,
            messageId: 'unexpected',
            data: { name: node.name },
            fix: (fixer) => fixer.replaceText(node, 'Bar'),
          });
        }
      },
    };
  },
};
```

### 2. Plugin entry (ESM, ESLint 9 flat)
```javascript
// index.js
import noFoo from './rules/no-foo.js';

const plugin = {
  meta: { name: 'eslint-plugin-acme', version: '1.0.0' },
  rules: { 'no-foo': noFoo },
};

plugin.configs = {
  recommended: {
    plugins: { acme: plugin },
    rules: { 'acme/no-foo': 'error' },
  },
};

export default plugin;
```

### 3. Consumer flat config
```javascript
// eslint.config.js
import acme from 'eslint-plugin-acme';

export default [
  acme.configs.recommended,
  { rules: { 'acme/no-foo': ['error'] } },
];
```

### 4. RuleTester (built-in test)
```javascript
import { RuleTester } from 'eslint';
import rule from '../rules/no-foo.js';

const tester = new RuleTester({
  languageOptions: { ecmaVersion: 2024, sourceType: 'module' },
});

tester.run('no-foo', rule, {
  valid: ['const Bar = 1;'],
  invalid: [{
    code: 'const Foo = 1;',
    errors: [{ messageId: 'unexpected' }],
    output: 'const Bar = 1;',
  }],
});
```

### 5. TypeScript rule with @typescript-eslint
```typescript
import { ESLintUtils } from '@typescript-eslint/utils';

const createRule = ESLintUtils.RuleCreator(
  (name) => `https://acme.dev/rules/${name}`,
);

export default createRule({
  name: 'no-any',
  meta: {
    type: 'suggestion',
    docs: { description: 'disallow any' },
    schema: [],
    messages: { noAny: 'Avoid any; use unknown.' },
  },
  defaultOptions: [],
  create(context) {
    return {
      TSAnyKeyword(node) {
        context.report({ node, messageId: 'noAny' });
      },
    };
  },
});
```

### 6. Suggestions (non-auto fix)
```javascript
context.report({
  node,
  messageId: 'considerRename',
  suggest: [{
    messageId: 'renameToBar',
    fix: (fixer) => fixer.replaceText(node, 'Bar'),
  }],
});
```

### 7. AST exploration (astexplorer.net)
```javascript
// Visitor pattern — leverage selector strings
return {
  'CallExpression[callee.name="eval"]'(node) {
    context.report({ node, message: 'eval disallowed' });
  },
};
```

### 8. Scope / variable analysis
```javascript
create(context) {
  return {
    Identifier(node) {
      const scope = context.sourceCode.getScope(node);
      const variable = scope.references.find((r) => r.identifier === node);
      if (variable?.resolved?.defs[0]?.type === 'ImportBinding') {
        // imported identifier
      }
    },
  };
}
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Codebase-specific 매 규칙 | Internal plugin (private npm). |
| OSS 공유 | Publish `eslint-plugin-foo`. |
| TS-only | `@typescript-eslint/utils` `RuleCreator`. |
| 매 codemod 용 | jscodeshift / ts-morph (ESLint fix 보다 more powerful). |
| 매 단순 ban API | `no-restricted-syntax` config — plugin 불필요. |

**기본값**: 매 ESLint 9 flat config + `@typescript-eslint/utils` RuleCreator.

## 🔗 Graph
- 부모: [[ESLint]] · [[AST]]
- 변형: [[Biome]]
- Adjacent: [[Prettier]] · [[TypeScript]]

## 🤖 LLM 활용
**언제**: AST visitor 작성, RuleTester case 생성, 매 selector string 의 작성.
**언제 X**: 매 cross-file 분석 (ESLint = single-file) — 매 ts-morph / lsif 사용.

## ❌ 안티패턴
- **Regex on source**: 매 source string regex 의 X — 매 AST 사용.
- **No tests**: 매 RuleTester 없는 rule 의 X — false positive 의 즉시 발생.
- **Auto-fix without safety**: 매 fix가 매 semantics 변경 시 `suggest` 사용.
- **`.eslintrc` in 2026**: 매 flat config 으로 migrate.

## 🧪 검증 / 중복
- Verified (ESLint 9 docs, eslint.org/docs/latest/extend).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — ESLint 9 flat config plugin authoring 패턴 |