Add prefer-event-target rule (#1792)

Co-authored-by: fisker Cheung <[email protected]>
Co-authored-by: Sindre Sorhus <[email protected]>

Author: 3 people

configs/recommended.js

@@ -78,6 +78,7 @@ module.exports = {
 		'unicorn/prefer-dom-node-dataset': 'error',
 		'unicorn/prefer-dom-node-remove': 'error',
 		'unicorn/prefer-dom-node-text-content': 'error',
+		'unicorn/prefer-event-target': 'error',
 		'unicorn/prefer-export-from': 'error',
 		'unicorn/prefer-includes': 'error',
 		'unicorn/prefer-json-parse-buffer': 'off',

docs/rules/prefer-event-target.md

@@ -0,0 +1,34 @@
+# Prefer `EventTarget` over `EventEmitter`
+
+<!-- Do not manually modify RULE_NOTICE part. Run: `npm run generate-rule-notices` -->
+<!-- RULE_NOTICE -->
+✅ *This rule is part of the [recommended](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config) config.*
+<!-- /RULE_NOTICE -->
+
+While [`EventEmitter`](https://nodejs.org/api/events.html#class-eventemitter) is only available in Node.js, [`EventTarget`](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget) is also available in *Deno* and browsers.
+
+This rule reduces the bundle size and makes your code more cross-platform friendly.
+
+See the [differences](https://nodejs.org/api/events.html#eventtarget-and-event-api) between `EventEmitter` and `EventTarget`.
+
+## Fail
+
+```js
+import {EventEmitter} from 'node:event';
+
+class Foo extends EventEmitter {}
+```
+
+```js
+const emitter = new EventEmitter();
+```
+
+## Pass
+
+```js
+class Foo extends EventTarget {}
+```
+
+```js
+const target = new EventTarget();
+```

readme.md

@@ -118,6 +118,7 @@ Each rule has emojis denoting:
 | [prefer-dom-node-dataset](docs/rules/prefer-dom-node-dataset.md) | Prefer using `.dataset` on DOM elements over calling attribute methods. | ✅ | 🔧 |  |
 | [prefer-dom-node-remove](docs/rules/prefer-dom-node-remove.md) | Prefer `childNode.remove()` over `parentNode.removeChild(childNode)`. | ✅ | 🔧 | 💡 |
 | [prefer-dom-node-text-content](docs/rules/prefer-dom-node-text-content.md) | Prefer `.textContent` over `.innerText`. | ✅ |  | 💡 |
+| [prefer-event-target](docs/rules/prefer-event-target.md) | Prefer `EventTarget` over `EventEmitter`. | ✅ |  |  |
 | [prefer-export-from](docs/rules/prefer-export-from.md) | Prefer `export…from` when re-exporting. | ✅ | 🔧 | 💡 |
 | [prefer-includes](docs/rules/prefer-includes.md) | Prefer `.includes()` over `.indexOf()` and `Array#some()` when checking for existence or non-existence. | ✅ | 🔧 | 💡 |
 | [prefer-json-parse-buffer](docs/rules/prefer-json-parse-buffer.md) | Prefer reading a JSON file as a buffer. |  | 🔧 |  |

rules/prefer-event-target.js

@@ -0,0 +1,39 @@
+'use strict';
+const {matches} = require('./selectors/index.js');
+
+const MESSAGE_ID = 'prefer-event-target';
+const messages = {
+	[MESSAGE_ID]: 'Prefer `EventTarget` over `EventEmitter`.',
+};
+
+const selector = [
+	'Identifier',
+	'[name="EventEmitter"]',
+	matches([
+		'ClassDeclaration > .superClass',
+		'ClassExpression > .superClass',
+		'NewExpression > .callee',
+	]),
+].join('');
+
+/** @param {import('eslint').Rule.RuleContext} context */
+const create = () => ({
+	[selector](node) {
+		return {
+			node,
+			messageId: MESSAGE_ID,
+		};
+	},
+});
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+	create,
+	meta: {
+		type: 'suggestion',
+		docs: {
+			description: 'Prefer `EventTarget` over `EventEmitter`.',
+		},
+		messages,
+	},
+};

test/prefer-event-target.mjs

@@ -0,0 +1,48 @@
+import outdent from 'outdent';
+import {getTester} from './utils/test.mjs';
+
+const {test} = getTester(import.meta);
+
+test.snapshot({
+	valid: [
+		'class Foo {}',
+		'class Foo extends OtherClass {}',
+		'class Foo extends EventTarget {}',
+		'const Foo = class extends EventTarget {}',
+		'const Foo = class extends foo.EventTarget {}',
+		'const Foo = class extends foo.bar.EventTarget {}',
+		'class Foo extends foo.EventEmitter {}',
+		'class Foo extends foo.bar.EventEmitter {}',
+		'class EventEmitter extends Foo {}',
+		'const Foo = class EventEmitter extends Foo {}',
+		'new Foo(EventEmitter)',
+		'new foo.EventEmitter()',
+	],
+	invalid: [
+		'class Foo extends EventEmitter {}',
+		'class Foo extends EventEmitter { someMethod() {} }',
+		'const Foo = class extends EventEmitter {}',
+		outdent`
+			class Foo extends EventEmitter {
+				addListener() {}
+				removeListener() {}
+			}
+		`,
+	],
+});
+
+test.snapshot({
+	valid: [
+		'EventTarget()',
+		'new EventTarget',
+		'const target = new EventTarget;',
+		'const target = EventTarget()',
+		'const target = new Foo(EventEmitter);',
+		'EventEmitter()',
+		'const emitter = EventEmitter()',
+	],
+	invalid: [
+		'new EventEmitter',
+		'const emitter = new EventEmitter;',
+	],
+});

test/snapshots/prefer-event-target.mjs.md

@@ -0,0 +1,71 @@
+# Snapshot report for `test/prefer-event-target.mjs`
+
+The actual snapshot is saved in `prefer-event-target.mjs.snap`.
+
+Generated by [AVA](https://avajs.dev).
+
+## Invalid #1
+      1 | class Foo extends EventEmitter {}
+
+> Error 1/1
+
+    `␊
+    > 1 | class Foo extends EventEmitter {}␊
+        |                   ^^^^^^^^^^^^ Prefer \`EventTarget\` over \`EventEmitter\`.␊
+    `
+
+## Invalid #2
+      1 | class Foo extends EventEmitter { someMethod() {} }
+
+> Error 1/1
+
+    `␊
+    > 1 | class Foo extends EventEmitter { someMethod() {} }␊
+        |                   ^^^^^^^^^^^^ Prefer \`EventTarget\` over \`EventEmitter\`.␊
+    `
+
+## Invalid #3
+      1 | const Foo = class extends EventEmitter {}
+
+> Error 1/1
+
+    `␊
+    > 1 | const Foo = class extends EventEmitter {}␊
+        |                           ^^^^^^^^^^^^ Prefer \`EventTarget\` over \`EventEmitter\`.␊
+    `
+
+## Invalid #4
+      1 | class Foo extends EventEmitter {
+      2 | 	addListener() {}
+      3 | 	removeListener() {}
+      4 | }
+
+> Error 1/1
+
+    `␊
+    > 1 | class Foo extends EventEmitter {␊
+        |                   ^^^^^^^^^^^^ Prefer \`EventTarget\` over \`EventEmitter\`.␊
+      2 | 	addListener() {}␊
+      3 | 	removeListener() {}␊
+      4 | }␊
+    `
+
+## Invalid #1
+      1 | new EventEmitter
+
+> Error 1/1
+
+    `␊
+    > 1 | new EventEmitter␊
+        |     ^^^^^^^^^^^^ Prefer \`EventTarget\` over \`EventEmitter\`.␊
+    `
+
+## Invalid #2
+      1 | const emitter = new EventEmitter;
+
+> Error 1/1
+
+    `␊
+    > 1 | const emitter = new EventEmitter;␊
+        |                     ^^^^^^^^^^^^ Prefer \`EventTarget\` over \`EventEmitter\`.␊
+    `