[eslint config] [*] [new] set ecmaVersion to 2017; enable object rest/spread; update babel-preset-airbnb

Author: ljharb

README.md

@@ -293,6 +293,26 @@ Other Style Guides
   console.log(has.call(object, key));
   ```
 
+  <a name="objects--rest-spread"></a>
+  - [3.10](#objects--rest-spread) Prefer the object spread operator over `Object.assign` to shallow-copy objects. Use the object rest operator to get a new object with certain properties omitted.
+
+  ```javascript
+  // very bad
+  const original = { a: 1, b: 2 };
+  const copy = Object.assign(original, { c: 3 }); // this mutates `original` ಠ_ಠ
+  delete copy.a; // so does this
+
+  // bad
+  const original = { a: 1, b: 2 };
+  const copy = Object.assign({}, original, { c: 3 }); // copy => { a: 1, b: 2, c: 3 }
+
+  // good
+  const original = { a: 1, b: 2 };
+  const copy = { ...original, c: 3 }; // copy => { a: 1, b: 2, c: 3 }
+
+  const { a, ...noA } = copy; // noA => { b: 2, c: 3 }
+  ```
+
 **[⬆ back to top](#table-of-contents)**
 
 ## Arrays

packages/eslint-config-airbnb-base/.eslintrc

@@ -4,5 +4,5 @@
     // disable requiring trailing commas because it might be nice to revert to
     // being JSON at some point, and I don't want to make big changes now.
     "comma-dangle": 0
-  }
+  },
 }

packages/eslint-config-airbnb-base/index.js

@@ -9,10 +9,13 @@ module.exports = {
     './rules/imports',
   ].map(require.resolve),
   parserOptions: {
-    ecmaVersion: 2016,
+    ecmaVersion: 2017,
     sourceType: 'module',
+    ecmaFeatures: {
+      experimentalObjectRestSpread: true,
+    },
   },
   rules: {
     strict: 'error',
-  }
+  },
 };

packages/eslint-config-airbnb-base/package.json

@@ -45,7 +45,7 @@
   },
   "homepage": "https://github.com/airbnb/javascript",
   "devDependencies": {
-    "babel-preset-airbnb": "^2.0.0",
+    "babel-preset-airbnb": "^2.1.0",
     "babel-tape-runner": "^2.0.1",
     "eslint": "^3.6.0",
     "eslint-find-rules": "^1.13.2",

packages/eslint-config-airbnb-base/rules/best-practices.js

@@ -187,6 +187,10 @@ module.exports = {
     }, {
       property: '__defineSetter__',
       message: 'Please use Object.defineProperty instead.',
+    }, {
+      object: 'Object',
+      property: 'assign',
+      message: 'Please use the object spread operator (...) instead.',
     }],
 
     // disallow use of assignment in return statement

packages/eslint-config-airbnb-base/test/.eslintrc

@@ -1,7 +1,6 @@
 {
   "rules": {
-    // disabled because I find it tedious to write tests while following this
-    // rule
+    // disabled because I find it tedious to write tests while following this rule
     "no-shadow": 0,
     // tests uses `t` for tape
     "id-length": [2, {"min": 2, "properties": "never", "exceptions": ["t"]}],

packages/eslint-config-airbnb-base/test/test-base.js

@@ -4,13 +4,15 @@ import test from 'tape';
 
 import index from '../';
 
-const files = { index };
+const files = { ...{ index } }; // object spread is to test parsing
 
 fs.readdirSync(path.join(__dirname, '../rules')).forEach((name) => {
   files[name] = require(`../rules/${name}`); // eslint-disable-line global-require
 });
 
-Object.keys(files).forEach((name) => {
+Object.keys(files).forEach((
+  name, // trailing function comma is to test parsing
+) => {
   const config = files[name];
 
   test(`${name}: does not reference react`, (t) => {

packages/eslint-config-airbnb/package.json

@@ -48,7 +48,7 @@
     "eslint-config-airbnb-base": "^7.1.0"
   },
   "devDependencies": {
-    "babel-preset-airbnb": "^2.0.0",
+    "babel-preset-airbnb": "^2.1.0",
     "babel-tape-runner": "^2.0.1",
     "eslint": "^3.6.0",
     "eslint-find-rules": "^1.13.2",