Setup repo

Author: vinassefranche

.gitignore

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+.yarn/*
+node_modules
+cjs
+*.tsbuildinfo
+!.yarn/releases

.yarn/releases/yarn-3.5.0.cjs

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+yarnPath: .yarn/releases/yarn-3.5.0.cjs
+
+nodeLinker: node-modules

.yarnrc.yml

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+# ESLint TypeScript custom rule
+This is an example of an ESLint custom rule written with TypeScript
+
+## How to test it
+- Run `yarn` to install the dependencies
+- Run `yarn workspace eslint-plugin-custom-rule build` to build the custom plugin
+- Run `yarn workspace app lint` to see the errors from the custom rule

Readme.md

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+{
+  "name": "eslint-typescript-custom-rule",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "workspaces": [
+    "packages/*"
+  ],
+  "packageManager": "yarn@3.5.0"
+}

package.json

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+module.exports = {
+  env: {
+    node: true,
+    es6: true,
+  },
+  parser: '@typescript-eslint/parser',
+  parserOptions: {
+    extraFileExtensions: ['.ts, .tsx'],
+  },
+  parserOptions: {
+    project: './tsconfig.json',
+    tsconfigRootDir: __dirname,
+  },
+  plugins: ['custom-rule'],
+  rules: {
+    'custom-rule/my-rule': 'error'
+  },
+};

packages/app/.eslintrc.js

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+{
+  "name": "app",
+  "version": "1.0.0",
+  "main": "cjs/index.js",
+  "module": "esm/index.js",
+  "private": true,
+  "devDependencies": {
+    "@typescript-eslint/parser": "^5.57.0",
+    "eslint": "^8.37.0",
+    "eslint-plugin-custom-rule": "workspace:*",
+    "typescript": "^5.0.3"
+  },
+  "scripts": {
+    "lint": "eslint --ext .ts ./src"
+  }
+}

packages/app/package.json

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+const foo = () => {}
+
+const bar = () => {}
+
+const fooBar = () => {}
+
+
+foo()
+bar()
+fooBar()

packages/app/src/index.ts

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+{
+  "compilerOptions": {
+    "sourceMap": true,
+    "inlineSources": true,
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "moduleResolution": "node",
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true,
+    "lib": ["esnext"],
+    "composite": true,
+    "incremental": true,
+    "declaration": true,
+    "declarationMap": true,
+    "rootDir": "src",
+    "skipLibCheck": true,
+    "outDir": "cjs",
+    "module": "commonjs",
+    "target": "es6",
+    "exactOptionalPropertyTypes": true,
+    "noUncheckedIndexedAccess": true
+  },
+  "include": ["src"]
+}

packages/app/tsconfig.json

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+{
+  "name": "eslint-plugin-custom-rule",
+  "version": "1.0.0",
+  "main": "cjs/index.js",
+  "private": true,
+  "dependencies": {
+    "@typescript-eslint/utils": "^5.57.0"
+  },
+  "devDependencies": {
+    "@typescript-eslint/parser": "^5.57.0",
+    "eslint": "^8.37.0",
+    "typescript": "^5.0.3",
+    "vitest": "^0.29.8"
+  },
+  "scripts": {
+    "build": "yarn tsc -b",
+    "test": "vitest"
+  }
+}

packages/eslint-plugin-custom-rule/package.json

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+import myRule from './myRule';
+
+export const rules = {
+  'my-rule': myRule,
+};

packages/eslint-plugin-custom-rule/src/index.ts

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+import { ESLintUtils } from '@typescript-eslint/utils';
+
+import myRule from './myRule';
+
+const parserResolver = require.resolve('@typescript-eslint/parser');
+
+const ruleTester = new ESLintUtils.RuleTester({
+  parser: parserResolver as any, // yarn 2+ shenanigans
+});
+
+ruleTester.run('my-rule', myRule, {
+  valid: ['notFooBar()', 'const foo = 2', 'const bar = 2'],
+  invalid: [
+    {
+      code: 'foo()',
+      errors: [{ messageId: 'messageIdForSomeFailure' }],
+    },
+    {
+      code: 'bar()',
+      errors: [{ messageId: 'messageIdForSomeOtherFailure' }],
+    },
+  ],
+});

packages/eslint-plugin-custom-rule/src/myRule.test.ts

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+import { TSESLint, AST_NODE_TYPES } from '@typescript-eslint/utils';
+
+type MessageIds = 'messageIdForSomeFailure' | 'messageIdForSomeOtherFailure';
+
+const myRule: TSESLint.RuleModule<MessageIds> = {
+  defaultOptions: [],
+  meta: {
+    type: 'suggestion',
+    messages: {
+      messageIdForSomeFailure: 'Error message for some failure',
+      messageIdForSomeOtherFailure: 'Error message for some other failure',
+    },
+    fixable: 'code',
+    schema: [], // no options
+  },
+  create: context => ({
+    CallExpression: node => {
+      if (node.callee.type !== AST_NODE_TYPES.Identifier) {
+        return;
+      }
+
+      if (node.callee.name === 'foo') {
+        return context.report({
+          node: node.callee,
+          messageId: 'messageIdForSomeFailure',
+        });
+      }
+      if (node.callee.name === 'bar') {
+        return context.report({
+          node: node.callee,
+          messageId: 'messageIdForSomeOtherFailure',
+        });
+      }
+
+      return;
+    },
+  }),
+};
+
+export default myRule;

packages/eslint-plugin-custom-rule/src/myRule.ts

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+{
+  "compilerOptions": {
+    "sourceMap": true,
+    "inlineSources": true,
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "moduleResolution": "node",
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true,
+    "lib": ["esnext"],
+    "composite": true,
+    "incremental": true,
+    "declaration": true,
+    "declarationMap": true,
+    "rootDir": "src",
+    "skipLibCheck": true,
+    "outDir": "cjs",
+    "module": "commonjs",
+    "target": "es6",
+    "exactOptionalPropertyTypes": true,
+    "noUncheckedIndexedAccess": true
+  },
+  "include": ["src"]
+}

packages/eslint-plugin-custom-rule/tsconfig.json

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+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    exclude: ['**/cjs/**'],
+  },
+});