chore: Rollup & Vitest

* Use Rollup instead of Babel to generate CJS and ESM bundles
* Convert implementation to ESM
* Use Vitest instead of Jest for tests
* Use memfs instead of mocking specific node:fs functions
* Update nps calls to use CJS config

Author: duncanbeevers

.eslintrc.js renamed to .eslintrc.cjs

@@ -2,10 +2,10 @@ const config = {
   extends: [
     'kentcdodds',
     'kentcdodds/jest',
-    'plugin:node-dependencies/recommended'
+    'plugin:node-dependencies/recommended',
   ],
   parserOptions: {
-    ecmaVersion: 2021
+    ecmaVersion: 2021,
   },
   rules: {
     'valid-jsdoc': 'off',
@@ -15,16 +15,16 @@ const config = {
       {
         anonymous: 'never',
         named: 'never',
-        asyncArrow: 'always'
-      }
+        asyncArrow: 'always',
+      },
     ],
     'import/no-import-module-exports': 'off',
     'arrow-parens': ['error', 'as-needed'],
     quotes: ['error', 'single', { avoidEscape: true }],
   },
   settings: {
-    'import/ignore': ['node_modules', 'src'] // Using CommonJS in src
-  }
+    'import/ignore': ['node_modules', 'src'], // Using CommonJS in src
+  },
 };
 
 module.exports = config;

.github/dependabot.yml

@@ -59,20 +59,41 @@ updates:
     - 17.3.9
     - 17.4.0
     - 17.4.1
+  - dependency-name: '@rollup/plugin-commonjs'
+    versions:
+    - 28.0.1
+  - dependency-name: '@rollup/plugin-json'
+    versions:
+    - 6.1.0
+  - dependency-name: '@rollup/plugin-node-resolve'
+    versions:
+    - 15.3.0
+  - dependency-name: rollup
+    versions:
+    - 4.28.0
+  - dependency-name: rollup-plugin-auto-external
+    versions:
+      - 2.0.0
+  - dependency-name: memfs
+    versions:
+    - 4.14.1
   - dependency-name: vue-eslint-parser
     versions:
     - 7.4.1
     - 7.5.0
     - 7.6.0
-  - dependency-name: jest-cli
+  - dependency-name: vite
+    versions:
+    - 6.0.3
+  - dependency-name: vitest
     versions:
-    - 26.6.3
-  - dependency-name: babel-jest
+    - 2.1.8
+  - dependency-name: '@vitest/coverage-v8'
     versions:
-    - 26.6.3
-  - dependency-name: jest
+    - 2.1.8
+  - dependency-name: '@vitest/ui'
     versions:
-    - 26.6.3
+    - 2.1.8
   - dependency-name: pretty-format
     versions:
     - 26.6.2

.prettierrc.js

@@ -22,23 +22,15 @@ module.exports = {
       // with ESM. ESM support is needed due to prettier v3’s use of a dynamic
       // `import()` in its `.cjs` file. The flag can be removed when node
       // supports modules in the VM API or the import is removed from prettier.
-      default: crossEnv(
-        'NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --coverage'
-      ),
-      update: crossEnv(
-        'NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --coverage --updateSnapshot'
-      ),
-      watch: crossEnv(
-        'NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --watch'
-      ),
+      default: crossEnv('vitest --coverage run'),
+      update: crossEnv('vitest --coverage --updateSnapshot'),
+      watch: crossEnv('vitest'),
       openCoverage: 'open coverage/lcov-report/index.html',
     },
     build: {
-      description: 'delete the dist directory and run babel to build the files',
-      script: series(
-        rimraf('dist'),
-        'babel --out-dir dist --ignore "src/__tests__/**/*","src/__mocks__/**/*" src'
-      ),
+      description:
+        'delete the dist directory and run Rollup to build the files',
+      script: series(rimraf('dist'), 'rollup -c'),
     },
     lint: {
       description: 'lint the entire project',
@@ -57,7 +49,11 @@ module.exports = {
     validate: {
       description:
         'This runs several scripts to make sure things look good before committing or on clean install',
-      script: concurrent.nps('lint', 'build', 'test'),
+      script: concurrent([
+        'nps -c ./package-scripts.cjs lint',
+        'nps -c ./package-scripts.cjs build',
+        'nps -c ./package-scripts.cjs test',
+      ]),
     },
     format: {
       description: 'Formats everything with prettier-eslint',

babel.config.js

@@ -2,12 +2,14 @@
   "name": "prettier-eslint",
   "version": "16.3.0",
   "description": "Formats your JavaScript using prettier followed by eslint --fix",
-  "main": "dist/index.js",
+  "main": "dist/index.cjs.js",
+  "module": "dist/index.esm.js",
   "types": "types/index.d.ts",
+  "type": "module",
   "scripts": {
     "prepare": "husky install",
-    "start": "nps",
-    "test": "nps test"
+    "start": "nps -c ./package-scripts.cjs",
+    "test": "nps -c ./package-scripts.cjs test"
   },
   "files": [
     "dist",
@@ -52,20 +54,29 @@
     "@babel/preset-env": "^7.22.9",
     "@changesets/changelog-github": "^0.4.8",
     "@changesets/cli": "^2.26.2",
+    "@rollup/plugin-commonjs": "^28.0.1",
+    "@rollup/plugin-json": "^6.1.0",
+    "@rollup/plugin-node-resolve": "^15.3.0",
     "@types/eslint": "^8.4.2",
+    "@vitest/coverage-v8": "^2.1.8",
+    "@vitest/ui": "^2.1.8",
     "all-contributors-cli": "^6.7.0",
     "eslint-config-kentcdodds": "^20.5.0",
     "eslint-plugin-node-dependencies": "^0.11.0",
     "husky": "^8.0.1",
     "jest": "^29.6.2",
+    "memfs": "^4.14.1",
     "nps": "^5.7.1",
     "nps-utils": "^1.3.0",
     "prettier-eslint-cli": "^8.0.0",
     "prettier-plugin-svelte": "^3.1.2",
     "rimraf": "^5.0.5",
+    "rollup": "^4.28.0",
+    "rollup-plugin-auto-external": "^2.0.0",
     "strip-indent": "^3.0.0",
     "svelte": "^4.2.9",
-    "svelte-eslint-parser": "^0.33.1"
+    "svelte-eslint-parser": "^0.33.1",
+    "vitest": "^2.1.8"
   },
   "engines": {
     "node": ">=16.10.0"

jest.config.js

@@ -0,0 +1,4 @@
+export default {
+  arrowParens: 'avoid',
+  singleQuote: true,
+};

package-scripts.js renamed to package-scripts.cjs

@@ -0,0 +1,31 @@
+import autoExternal from 'rollup-plugin-auto-external';
+import commonjs from '@rollup/plugin-commonjs';
+import json from '@rollup/plugin-json';
+import { nodeResolve } from '@rollup/plugin-node-resolve';
+
+export default {
+  input: 'src/index.mjs',
+  output: [
+    {
+      file: 'dist/cjs/index.js',
+      format: 'cjs',
+      name: 'cjs-bundle',
+    },
+    {
+      file: 'dist/esm/index.js',
+      format: 'esm',
+      name: 'esm-bundle',
+    },
+  ],
+  external: ['fs', 'node:path'],
+  plugins: [
+    autoExternal(),
+    commonjs({
+      include: /node_modules/,
+      requireReturnsDefault: 'auto',
+      strictRequires: 'debug',
+    }),
+    nodeResolve({ preferBuiltins: true }),
+    json(),
+  ],
+};

package.json

@@ -1,40 +1,16 @@
+import { vi } from 'vitest';
+
 // this mock file is so eslint doesn't attempt to actually
 // search around the file system for stuff
 
-const eslint = jest.requireActual('eslint');
-const { ESLint } = eslint;
-
-const mockCalculateConfigForFileSpy = jest.fn(mockCalculateConfigForFile);
-mockCalculateConfigForFileSpy.overrides = {};
-const mockLintTextSpy = jest.fn(mockLintText);
-
-module.exports = Object.assign(eslint, {
-  ESLint: jest.fn(MockESLint),
-  mock: {
-    calculateConfigForFile: mockCalculateConfigForFileSpy,
-    lintText: mockLintTextSpy
-  }
-});
-
-function MockESLint(...args) {
-  global.__PRETTIER_ESLINT_TEST_STATE__.eslintPath = __filename;
-  const eslintInstance = new ESLint(...args);
-  eslintInstance.calculateConfigForFile = mockCalculateConfigForFileSpy;
-  eslintInstance._originalLintText = eslintInstance.lintText;
-  eslintInstance.lintText = mockLintTextSpy;
-  return eslintInstance;
-}
-
-MockESLint.prototype = Object.create(ESLint.prototype);
+const eslintActual = await vi.importActual('eslint');
+const { ESLint } = eslintActual;
 
 // eslint-disable-next-line complexity
 function mockCalculateConfigForFile(filePath) {
-  if (mockCalculateConfigForFileSpy.throwError) {
-    throw mockCalculateConfigForFileSpy.throwError;
-  }
   if (!filePath) {
     return {
-      rules: {}
+      rules: {},
     };
   }
   if (filePath.includes('default-config')) {
@@ -46,7 +22,7 @@ function mockCalculateConfigForFile(filePath) {
         quotes: [
           2,
           'single',
-          { avoidEscape: true, allowTemplateLiterals: true }
+          { avoidEscape: true, allowTemplateLiterals: true },
         ],
         'comma-dangle': [
           2,
@@ -55,26 +31,44 @@ function mockCalculateConfigForFile(filePath) {
             objects: 'always-multiline',
             imports: 'always-multiline',
             exports: 'always-multiline',
-            functions: 'always-multiline'
-          }
+            functions: 'always-multiline',
+          },
         ],
-        'arrow-parens': [2, 'as-needed']
-      }
+        'arrow-parens': [2, 'as-needed'],
+      },
     };
   } else if (filePath.includes('fixtures/paths')) {
     return { rules: {} };
   } else {
     throw new Error(
       `Your mock filePath (${filePath})` +
-        ' does not have a handler for finding the config'
+        ' does not have a handler for finding the config',
     );
   }
 }
 
-function mockLintText(...args) {
+const mockLintTextSpy = vi.fn(function mockLintText(...args) {
   /* eslint no-invalid-this:0 */
   if (mockLintTextSpy.throwError) {
     throw mockLintTextSpy.throwError;
   }
   return this._originalLintText(...args);
+});
+
+const calculateConfigForFileSpy = vi.spyOn(ESLint.prototype, 'calculateConfigForFile').mockImplementation(mockCalculateConfigForFile);
+const lintTextSpy = vi.spyOn(ESLint.prototype, 'lintText');
+
+function MockESLint(...args) {
+  global.__PRETTIER_ESLINT_TEST_STATE__.eslintPath = __filename;
+  return new ESLint(...args);
 }
+
+export default {
+  ...eslintActual.default,
+  ESLint: vi.fn(MockESLint),
+};
+
+export const helpers = {
+  getCalculateConfigForFileSpy: () => calculateConfigForFileSpy,
+  getLintTextSpy: () => lintTextSpy,
+};

prettier.config.mjs

@@ -0,0 +1,25 @@
+// This follows the advice of the Vitest Mocking guide, and mocks the full
+// filesystem with an in-memory replacement.
+// https://vitest.dev/guide/mocking#file-system
+const { createFsFromVolume, memfs, Volume } = require('memfs');
+import path from 'node:path';
+
+const files = [
+  'foo.js',
+  'package.json',
+  'node_modules/eslint/index.js',
+  'node_modules/prettier/index.js',
+];
+
+const volume = new Volume();
+
+volume.fromJSON(
+  Object.fromEntries(
+    files.map(file => {
+      return [`./${file}`, `.tests/fixtures/paths/${file}`];
+    }),
+  ),
+  `${path.dirname(__filename)}/../../tests/fixtures/paths`,
+);
+
+export default createFsFromVolume(volume);