Add prefer-find rule

docs/rules/prefer-find.md

@@ -0,0 +1,21 @@
+# Prefer `.find(…)` over first element of `.filter(…)` result
+
+[`Array#find`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find) breaks the loop as soon as it finds a match.
+
+This rule is fixable.
+
+## Fail
+
+```js
+const item = array.filter(x => x === '🦄')[0];
+```
+
+```js
+const item = array.filter(x => x === '🦄').shift();
+```
+
+## Pass
+
+```js
+const item = array.find(x => x === '🦄');
+```

index.js

@@ -50,6 +50,7 @@ module.exports = {
 				'unicorn/prefer-add-event-listener': 'error',
 				'unicorn/prefer-dataset': 'error',
 				'unicorn/prefer-event-key': 'error',
+				'unicorn/prefer-find': 'error',
 				'unicorn/prefer-flat-map': 'error',
 				'unicorn/prefer-includes': 'error',
 				'unicorn/prefer-modern-dom-apis': 'error',

readme.md

@@ -66,6 +66,7 @@ Configure it in `package.json`.
 			"unicorn/prefer-add-event-listener": "error",
 			"unicorn/prefer-dataset": "error",
 			"unicorn/prefer-event-key": "error",
+			"unicorn/prefer-find": "error",
 			"unicorn/prefer-flat-map": "error",
 			"unicorn/prefer-includes": "error",
 			"unicorn/prefer-modern-dom-apis": "error",
@@ -126,6 +127,7 @@ Configure it in `package.json`.
 - [prefer-add-event-listener](docs/rules/prefer-add-event-listener.md) - Prefer `.addEventListener()` and `.removeEventListener()` over `on`-functions. *(partly fixable)*
 - [prefer-dataset](docs/rules/prefer-dataset.md) - Prefer using `.dataset` on DOM elements over `.setAttribute(…)`. *(fixable)*
 - [prefer-event-key](docs/rules/prefer-event-key.md) - Prefer `KeyboardEvent#key` over `KeyboardEvent#keyCode`. *(partly fixable)*
+- [prefer-find](docs/rules/prefer-find.md) - Prefer `.find(…)` over first element of `.filter(…)` result. *(fixable)*
 - [prefer-flat-map](docs/rules/prefer-flat-map.md) - Prefer `.flatMap(…)` over `.map(…).flat()`. *(fixable)*
 - [prefer-includes](docs/rules/prefer-includes.md) - Prefer `.includes()` over `.indexOf()` when checking for existence or non-existence. *(fixable)*
 - [prefer-modern-dom-apis](docs/rules/prefer-modern-dom-apis.md) - Prefer `.before()` over `.insertBefore()`, `.replaceWith()` over `.replaceChild()`, prefer one of `.before()`, `.after()`, `.append()` or `.prepend()` over `insertAdjacentText()` and `insertAdjacentElement()`. *(fixable)*

rules/prefer-find.js

@@ -0,0 +1,72 @@
+'use strict';
+const getDocumentationUrl = require('./utils/get-documentation-url');
+const methodSelector = require('./utils/method-selector');
+
+const MESSAGE_ID_ZERO_INDEX = 'prefer-find-over-filter-zero-index';
+const MESSAGE_ID_SHIFT = 'prefer-find-over-filter-shift';
+
+const zeroIndexSelector = [
+	'MemberExpression',
+	'[computed=true]',
+	'[property.type="Literal"]',
+	'[property.raw="0"]',
+	methodSelector({
+		name: 'filter',
+		min: 1,
+		max: 2,
+		property: 'object'
+	})
+].join('');
+
+const shiftSelector = [
+	methodSelector({
+		name: 'shift',
+		length: 0
+	}),
+	methodSelector({
+		name: 'filter',
+		min: 1,
+		max: 2,
+		property: 'callee.object'
+	})
+].join('');
+
+const create = context => {
+	return {
+		[zeroIndexSelector](node) {
+			context.report({
+				node,
+				messageId: MESSAGE_ID_ZERO_INDEX,
+				fix: fixer => [
+					fixer.replaceText(node.object.callee.property, 'find'),
+					fixer.removeRange([node.object.range[1], node.range[1]])
+				]
+			});
+		},
+		[shiftSelector](node) {
+			context.report({
+				node,
+				messageId: MESSAGE_ID_SHIFT,
+				fix: fixer => [
+					fixer.replaceText(node.callee.object.callee.property, 'find'),
+					fixer.removeRange([node.callee.object.range[1], node.range[1]])
+				]
+			});
+		}
+	};
+};
+
+module.exports = {
+	create,
+	meta: {
+		type: 'suggestion',
+		docs: {
+			url: getDocumentationUrl(__filename)
+		},
+		fixable: 'code',
+		messages: {
+			[MESSAGE_ID_ZERO_INDEX]: 'Prefer `.find(…)` over `.filter(…)[0]`.',
+			[MESSAGE_ID_SHIFT]: 'Prefer `.find(…)` over `.filter(…).shift()`.'
+		}
+	}
+};

rules/utils/method-selector.js

@@ -25,7 +25,7 @@ module.exports = options => {
 	];
 
 	if (name) {
-		selector.push(`[callee.property.name="${name}"]`);
+		selector.push(`[${prefix}callee.property.name="${name}"]`);
 	}
 
 	if (Array.isArray(names) && names.length !== 0) {

test/prefer-find.js

@@ -0,0 +1,113 @@
+import test from 'ava';
+import {outdent} from 'outdent';
+import avaRuleTester from 'eslint-ava-rule-tester';
+import rule from '../rules/prefer-find';
+
+const MESSAGE_ID_ZERO_INDEX = 'prefer-find-over-filter-zero-index';
+const MESSAGE_ID_SHIFT = 'prefer-find-over-filter-shift';
+
+const ruleTester = avaRuleTester(test, {
+	parserOptions: {
+		ecmaVersion: 2020
+	}
+});
+
+ruleTester.run('prefer-find', rule, {
+	valid: [
+		'array.find(foo)',
+
+		// Test `[0]`
+		'array.filter(foo)',
+		'array.filter(foo)[+0]',
+		'array.filter(foo)[-0]',
+		'array.filter(foo)[1-1]',
+		'array.filter(foo)["0"]',
+		'array.filter(foo).first',
+
+		// Test `.shift()`
+		// Not `CallExpression`
+		'array.filter(foo).shift',
+		// Not `MemberExpression`
+		'shift(array.filter(foo))',
+		// `callee.property` is not a `Identifier`
+		'array.filter(foo)["shift"]()',
+		// Computed
+		'array.filter(foo)[shift]()',
+		// Not `shift`
+		'array.filter(foo).notShift()',
+		// More or less argument(s)
+		'array.filter(foo).shift(extraArgument)',
+		'array.filter(foo).shift(...[])',
+
+		// Test `.filter()`
+		// Not `CallExpression`
+		'array.filter[0]',
+		'array.filter.shift()',
+		// Not `MemberExpression`
+		'filter(foo)[0]',
+		'filter(foo).shift()',
+		// `callee.property` is not a `Identifier`
+		'array["filter"](foo)[0]',
+		'array["filter"](foo).shift()',
+		// Computed
+		'array[filter](foo)[0]',
+		'array[filter](foo).shift()',
+		// Not `filter`
+		'array.notFilter(foo)[0]',
+		'array.notFilter(foo).shift()',
+		// More or less argument(s)
+		'array.filter()[0]',
+		'array.filter(foo, thisArgument, extraArgument)[0]',
+		'array.filter(...foo)[0]',
+		'array.filter().shift()',
+		'array.filter(foo, thisArgument, extraArgument).shift()',
+		'array.filter(...foo).shift()'
+	],
+	invalid: [
+		{
+			code: 'array.filter(foo)[0]',
+			output: 'array.find(foo)',
+			errors: [{messageId: MESSAGE_ID_ZERO_INDEX}]
+		},
+		{
+			code: 'array.filter(foo).shift()',
+			output: 'array.find(foo)',
+			errors: [{messageId: MESSAGE_ID_SHIFT}]
+		},
+		{
+			code: 'array.filter(foo, thisArgument)[0]',
+			output: 'array.find(foo, thisArgument)',
+			errors: [{messageId: MESSAGE_ID_ZERO_INDEX}]
+		},
+		{
+			code: 'array.filter(foo, thisArgument).shift()',
+			output: 'array.find(foo, thisArgument)',
+			errors: [{messageId: MESSAGE_ID_SHIFT}]
+		},
+		{
+			code: outdent`
+				const item = array
+					// comment 1
+					.filter(
+						// comment 2
+						x => x === '🦄'
+					)
+					// comment 3
+					.shift()
+					// comment 4
+					;
+			`,
+			output: outdent`
+				const item = array
+					// comment 1
+					.find(
+						// comment 2
+						x => x === '🦄'
+					)
+					// comment 4
+					;
+			`,
+			errors: [{messageId: MESSAGE_ID_SHIFT}]
+		}
+	]
+});