chore: add eslint alongside prettier

.eslintrc.js

@@ -0,0 +1,36 @@
+module.exports = {
+  env: {
+    node: true
+  },
+  extends: [
+    'prettier',
+    'eslint:recommended',
+    'plugin:@typescript-eslint/recommended'
+  ],
+  parser: '@typescript-eslint/parser',
+  parserOptions: {
+    ecmaVersion: 'latest',
+    sourceType: 'module'
+  },
+  plugins: ['prettier', '@typescript-eslint'],
+  rules: {
+    'prettier/prettier': ['error'],
+    '@typescript-eslint/no-extra-semi': 'off',
+    'no-restricted-imports': [
+      'error',
+      {
+        patterns: ['src/*']
+      }
+    ],
+
+    // Currently, disabled to avoid a lot of changes during migration
+    '@typescript-eslint/no-explicit-any': 'off',
+    '@typescript-eslint/no-non-null-assertion': 'off',
+    '@typescript-eslint/no-unused-vars': 'off',
+    '@typescript-eslint/ban-types': 'off',
+    '@typescript-eslint/no-empty-function': 'off',
+    '@typescript-eslint/ban-ts-comment': 'off',
+    'prefer-const': 'off',
+    'no-prototype-builtins': 'off'
+  }
+}

package.json

@@ -22,13 +22,18 @@
     "@types/jest": "27.4.1",
     "@types/node": "17.0.23",
     "@types/pretty": "^2.0.1",
+    "@typescript-eslint/eslint-plugin": "^5.18.0",
+    "@typescript-eslint/parser": "^5.18.0",
     "@vue/babel-plugin-jsx": "^1.1.1",
     "@vue/compat": "3.2.31",
     "@vue/compiler-dom": "3.2.31",
     "@vue/compiler-sfc": "3.2.31",
     "@vue/vue3-jest": "27.0.0-alpha.4",
     "babel-jest": "27.5.1",
     "babel-preset-jest": "27.5.1",
+    "eslint": "^8.12.0",
+    "eslint-config-prettier": "^8.5.0",
+    "eslint-plugin-prettier": "^4.0.0",
     "husky": "^7.0.4",
     "jest": "27.5.1",
     "jsdom": "^19.0.0",
@@ -62,8 +67,8 @@
     "test:build": "yarn jest --runInBand tests/ -use-build",
     "tsd": "tsc -p test-dts/tsconfig.tsd.json",
     "build": "yarn rollup -c rollup.config.js",
-    "lint": "prettier -c \"(src|tests)/**/*.(ts?(x)|vue)\"",
-    "lint:fix": "yarn lint --write",
+    "lint": "eslint --ext .ts src/ tests/",
+    "lint:fix": "yarn lint --fix",
     "docs:dev": "vitepress dev docs",
     "docs:build": "vitepress build docs",
     "vue-tsc": "vue-tsc --noEmit -p tsconfig.volar.json",
@@ -76,7 +81,7 @@
   },
   "lint-staged": {
     "*.ts": [
-      "prettier --parser=typescript --write"
+      "eslint --fix"
     ],
     "*.md": [
       "prettier --write"
@@ -97,5 +102,4 @@
     "url": "git+https://github.com/vuejs/test-utils.git"
   },
   "homepage": "https://github.com/vuejs/test-utils"
-
 }

src/domWrapper.ts

@@ -66,7 +66,7 @@ export class DOMWrapper<NodeType extends Node> extends BaseWrapper<NodeType> {
     return results.filter((r: WrapperLike) => this.element.contains(r.element))
   }
 
-  private async setChecked(checked: boolean = true) {
+  private async setChecked(checked = true) {
     // typecast so we get type safety
     const element = this.element as unknown as HTMLInputElement
     const type = this.attributes().type

src/stubs.ts

@@ -141,8 +141,8 @@ function createStubOnceForType(
 
 export function stubComponents(
   stubs: Stubs = {},
-  shallow: boolean = false,
-  renderStubDefaultSlot: boolean = false
+  shallow = false,
+  renderStubDefaultSlot = false
 ) {
   const createdStubsMap: WeakMap<{} & VNodeTypes, ConcreteComponent> =
     new WeakMap()

tests/features/classComponent.spec.ts

@@ -50,7 +50,7 @@ describe('class component', () => {
   })
 
   it('methods', () => {
-    let msg: string = ''
+    let msg = ''
 
     class MyComp extends Vue {
       hello() {