test: eslint setup (#981)

* chore: eslint setup

* build: update circleci config

* build: fix circleci config

.circleci/config.yml

@@ -29,6 +29,11 @@ commands:
       - run:
           name: Lint project
           command: yarn lint
+  format:
+    steps:
+      - run:
+          name: Format project
+          command: yarn format
   deps:
     steps:
       - run:
@@ -56,6 +61,7 @@ commands:
       - save-cache
       - build
       - lint
+      - format
       - deps
       - test
   run-tests:

.eslintignore

@@ -0,0 +1,4 @@
+lib/
+coverage/
+node_modules/
+fixtures/

.eslintrc.js

@@ -0,0 +1,74 @@
+module.exports = {
+	root: true,
+	plugins: ['@typescript-eslint', 'jest', 'import'],
+	env: {
+		es6: true,
+		node: true
+	},
+	parserOptions: {
+		sourceType: 'module',
+		ecmaVersion: 11,
+		ecmaFeatures: {
+			jsx: false
+		}
+	},
+	extends: ['eslint:recommended', 'prettier'],
+	rules: {
+		// disallow non-import statements appearing before import statements
+		'import/first': 'error',
+		// Forbid import of modules using absolute paths
+		'import/no-absolute-path': 'error',
+		// disallow AMD require/define
+		'import/no-amd': 'error',
+		// Forbid mutable exports
+		'import/no-mutable-exports': 'error',
+		// Prevent importing the default as if it were named
+		'import/no-named-default': 'error',
+		// Forbid a module from importing itself
+		'import/no-self-import': 'error'
+
+		// Enable after https://github.com/benmosher/eslint-plugin-import/issues/1650 is fixed
+		// Forbid the use of extraneous packages
+		// 'import/no-extraneous-dependencies': [
+		// 	'error',
+		// 	{devDependencies: ['**/*.test.js']}
+		// ]
+	},
+	overrides: [
+		{
+			files: ['*.ts'],
+			parser: '@typescript-eslint/parser',
+			extends: [
+				'plugin:@typescript-eslint/eslint-recommended',
+				'plugin:@typescript-eslint/recommended',
+				'prettier/@typescript-eslint'
+			],
+			rules: {
+				'@typescript-eslint/no-unused-vars': 'off',
+				'@typescript-eslint/no-use-before-define': 'off',
+				'@typescript-eslint/no-explicit-any': 'off',
+				'@typescript-eslint/explicit-function-return-type': 'off',
+				'@typescript-eslint/no-var-requires': 'off',
+				'@typescript-eslint/no-inferrable-types': 'off',
+				'@typescript-eslint/no-non-null-assertion': 'off',
+
+				// TODO: enable those rules?
+				'no-empty': 'off',
+				'no-var': 'off'
+			}
+		},
+		{
+			files: ['*.test.ts', '*.test.js'],
+			env: {
+				jest: true
+			},
+			extends: ['plugin:jest/recommended'],
+			rules: {
+				'@typescript-eslint/no-explicit-any': 'off',
+				'@typescript-eslint/no-var-requires': 'off',
+				// disallow non-import statements appearing before import statements
+				'import/first': 'off'
+			}
+		}
+	]
+};

.prettierignore

@@ -1,2 +1,5 @@
 lib/
+coverage/
+node_modules/
+fixtures/
 CHANGELOG.md

package.json

@@ -12,7 +12,10 @@
     "deps": "lerna run deps",
     "pkg": "lerna run pkg",
     "docs": "docsify serve docs",
-    "lint": "prettier **/*.{ts,js,json,yml,md} -l",
+    "lint": "eslint . --ext .js,.ts",
+    "lint-fix": "eslint . --ext .js,.ts --fix",
+    "format": "prettier **/*.{ts,js,json,yml,md} -l",
+    "format-fix": "prettier **/*.{ts,js,json,yml,md} --write",
     "publish": "lerna publish --conventional-commits",
     "reinstall": "yarn clean && yarn install",
     "start": "lerna run start --stream --parallel --include-dependencies",
@@ -75,18 +78,24 @@
   },
   "devDependencies": {
     "@lerna/project": "3.18.0",
-    "@types/node": "12.12.26",
     "@types/jest": "25.1.2",
+    "@types/node": "12.12.26",
+    "@typescript-eslint/eslint-plugin": "^2.19.0",
+    "@typescript-eslint/parser": "^2.19.0",
     "docsify-cli": "^4.4.0",
+    "eslint": "^6.8.0",
+    "eslint-config-prettier": "^6.10.0",
+    "eslint-plugin-import": "^2.20.1",
+    "eslint-plugin-jest": "^23.6.0",
     "husky": "4.2.1",
     "jest": "25.1.0",
     "lerna": "3.20.2",
+    "lerna-v2": "npm:lerna@2",
+    "lerna-v3": "npm:lerna@3",
     "lint-staged": "10.0.7",
     "prettier": "1.17.1",
     "ts-jest": "25.2.0",
-    "typescript": "3.7.5",
-    "lerna-v2": "npm:lerna@2",
-    "lerna-v3": "npm:lerna@3"
+    "typescript": "3.7.5"
   },
   "husky": {
     "hooks": {