Add prefer-at rule (#1331)

Author: fisker

docs/rules/prefer-array-flat-map.md

@@ -36,4 +36,4 @@ const foo = bar.flat().map(element => unicorn(element));
 
 ## Related rules
 
-- [prefer-array-flat](./prefer-array-flat.md)
+- [unicorn/prefer-array-flat](./prefer-array-flat.md)

docs/rules/prefer-array-flat.md

@@ -99,4 +99,4 @@ const foo = utils.flat(bar); // Fails
 
 ## Related rules
 
-- [prefer-array-flat-map](./prefer-array-flat-map.md)
+- [unicorn/prefer-array-flat-map](./prefer-array-flat-map.md)

docs/rules/prefer-at.md

@@ -0,0 +1,122 @@
+# Prefer `.at()` method for index access and `String#charAt()`
+
+Prefer [`Array#at()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at), [`String#at()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/at), and `{TypedArray,NodeList,CSSRuleList,…}#at()` for index access and `String#charAt()`.
+
+This rule is fixable.
+
+## Fail
+
+```js
+const foo = array[array.length - 1];
+```
+
+```js
+const foo = array[array.length - 5];
+```
+
+```js
+const foo = array.slice(-1)[0];
+```
+
+```js
+const foo = array.slice(-1).pop();
+```
+
+```js
+const foo = array.slice(-5).shift();
+```
+
+```js
+const foo = string.charAt(string.length - 5);
+```
+
+```js
+const foo = lodash.last(array);
+```
+
+## Pass
+
+```js
+const foo = array.at(-1);
+```
+
+```js
+const foo = array.at(-5);
+```
+
+```js
+const foo = array[100];
+```
+
+```js
+// This rule is not checking this case, but `unicorn/prefer-negative-index` rule will fix it.
+const foo = array.at(array.length - 1);
+```
+
+```js
+array[array.length - 1] = foo;
+```
+
+## Options
+
+Type: `object`
+
+### checkAllIndexAccess
+
+Type: `boolean`\
+Default: `false`
+
+This rule only check negative indexes by default, but you can also check positive indexes by setting `checkAllIndexAccess` to `true`.
+
+Example:
+
+```js
+{
+	'unicorn/prefer-at': [
+		'error',
+		{
+			checkAllIndexAccess: true
+		}
+	]
+}
+```
+
+```js
+// eslint unicorn/prefer-at: ["error", {"checkAllIndexAccess": true}]
+const foo = bar[10]; // Fails, will fix to `bar.at(10)`
+const foo = bar[unknownProperty]; // Passes
+const foo = string.chatAt(unknownIndex); // Fails
+```
+
+### getLastElementFunctions
+
+Type: `string[]`
+
+You can also check custom functions that get last element of objects.
+
+`_.last()`, `lodash.last()`, and `underscore.last()` are checked by default.
+
+Example:
+
+```js
+{
+	'unicorn/prefer-at': [
+		'error',
+		{
+			getLastElementFunctions: [
+				'getLast',
+				'utils.lastElement'
+			]
+		}
+	]
+}
+```
+
+```js
+// eslint unicorn/prefer-at: ["error", {"getLastElementFunctions": ["utils.lastElement"]}]
+const foo = utils.lastElement(bar); // Fails
+```
+
+## Related rules
+
+- [unicorn/prefer-negative-index](./prefer-negative-index.md)

docs/rules/prefer-negative-index.md

@@ -47,3 +47,7 @@ Array.prototype.slice.call(foo, -2, -1);
 ```js
 Array.prototype.slice.apply(foo, [-2, -1]);
 ```
+
+## Related rules
+
+- [unicorn/prefer-at](./prefer-at.md)

index.js

@@ -87,6 +87,8 @@ module.exports = {
 				'unicorn/prefer-array-flat-map': 'error',
 				'unicorn/prefer-array-index-of': 'error',
 				'unicorn/prefer-array-some': 'error',
+				// TODO: Enable this by default when targeting a Node.js version that supports `Array#at`.
+				'unicorn/prefer-at': 'off',
 				'unicorn/prefer-date-now': 'error',
 				'unicorn/prefer-default-parameters': 'error',
 				'unicorn/prefer-dom-node-append': 'error',
@@ -101,7 +103,7 @@ module.exports = {
 				'unicorn/prefer-negative-index': 'error',
 				'unicorn/prefer-node-protocol': 'error',
 				'unicorn/prefer-number-properties': 'error',
-				// TODO: Enable this by default when targeting Node.js support `Object.hasOwn`.
+				// TODO: Enable this by default when targeting a Node.js version that supports `Object.hasOwn`.
 				'unicorn/prefer-object-has-own': 'off',
 				'unicorn/prefer-optional-catch-binding': 'error',
 				'unicorn/prefer-prototype-methods': 'error',

readme.md

@@ -83,6 +83,7 @@ Configure it in `package.json`.
 			"unicorn/prefer-array-flat-map": "error",
 			"unicorn/prefer-array-index-of": "error",
 			"unicorn/prefer-array-some": "error",
+			"unicorn/prefer-at": "off",
 			"unicorn/prefer-date-now": "error",
 			"unicorn/prefer-default-parameters": "error",
 			"unicorn/prefer-dom-node-append": "error",
@@ -183,6 +184,7 @@ Each rule has emojis denoting:
 | [prefer-array-flat-map](docs/rules/prefer-array-flat-map.md) | Prefer `.flatMap(…)` over `.map(…).flat()`. | ✅ | 🔧 |  |
 | [prefer-array-index-of](docs/rules/prefer-array-index-of.md) | Prefer `Array#indexOf()` over `Array#findIndex()` when looking for the index of an item. | ✅ | 🔧 | 💡 |
 | [prefer-array-some](docs/rules/prefer-array-some.md) | Prefer `.some(…)` over `.find(…)`. | ✅ |  | 💡 |
+| [prefer-at](docs/rules/prefer-at.md) | Prefer `.at()` method for index access and `String#charAt()`. |  | 🔧 | 💡 |
 | [prefer-date-now](docs/rules/prefer-date-now.md) | Prefer `Date.now()` to get the number of milliseconds since the Unix Epoch. | ✅ | 🔧 |  |
 | [prefer-default-parameters](docs/rules/prefer-default-parameters.md) | Prefer default parameters over reassignment. | ✅ | 🔧 | 💡 |
 | [prefer-dom-node-append](docs/rules/prefer-dom-node-append.md) | Prefer `Node#append()` over `Node#appendChild()`. | ✅ | 🔧 |  |

rules/consistent-destructuring.js

@@ -1,7 +1,7 @@
 'use strict';
 const avoidCapture = require('./utils/avoid-capture');
 const getDocumentationUrl = require('./utils/get-documentation-url');
-const {not} = require('./selectors');
+const {not, notLeftHandSideSelector} = require('./selectors');
 
 const MESSAGE_ID = 'consistentDestructuring';
 const MESSAGE_ID_SUGGEST = 'consistentDestructuringSuggest';
@@ -16,12 +16,10 @@ const declaratorSelector = [
 const memberSelector = [
 	'MemberExpression',
 	'[computed!=true]',
+	notLeftHandSideSelector(),
 	not([
-		'AssignmentExpression > .left',
 		'CallExpression > .callee',
-		'NewExpression > .callee',
-		'UpdateExpression > .argument',
-		'UnaryExpression[operator="delete"] > .argument'
+		'NewExpression> .callee'
 	])
 ].join('');