prefer-event-target: Ignore EventEmitter from @angular/core and eventemitter3 (#2197)

Author: fisker

rules/prefer-event-target.js

@@ -1,12 +1,82 @@
 'use strict';
+const {findVariable} = require('@eslint-community/eslint-utils');
+const {getAncestor} = require('./utils/index.js');
+const {isStaticRequire, isStringLiteral, isMemberExpression} = require('./ast/index.js');
 
 const MESSAGE_ID = 'prefer-event-target';
 const messages = {
 	[MESSAGE_ID]: 'Prefer `EventTarget` over `EventEmitter`.',
 };
 
+const packagesShouldBeIgnored = new Set([
+	'@angular/core',
+	'eventemitter3',
+]);
+
+const isConstVariableDeclarationId = node =>
+	node.parent.type === 'VariableDeclarator'
+	&& node.parent.id === node
+	&& node.parent.parent.type === 'VariableDeclaration'
+	&& node.parent.parent.kind === 'const'
+	&& node.parent.parent.declarations.includes(node.parent);
+
+function isAwaitImportOrRequireFromIgnoredPackages(node) {
+	if (!node) {
+		return false;
+	}
+
+	let source;
+	if (isStaticRequire(node)) {
+		[source] = node.arguments;
+	} else if (node.type === 'AwaitExpression' && node.argument.type === 'ImportExpression') {
+		({source} = node.argument);
+	}
+
+	if (isStringLiteral(source) && packagesShouldBeIgnored.has(source.value)) {
+		return true;
+	}
+
+	return false;
+}
+
+function isFromIgnoredPackage(node) {
+	if (!node) {
+		return false;
+	}
+
+	const importDeclaration = getAncestor(node, 'ImportDeclaration');
+	if (packagesShouldBeIgnored.has(importDeclaration?.source.value)) {
+		return true;
+	}
+
+	// `const {EventEmitter} = ...`
+	if (
+		node.parent.type === 'Property'
+		&& node.parent.value === node
+		&& node.parent.key.type === 'Identifier'
+		&& node.parent.key.name === 'EventEmitter'
+		&& node.parent.parent.type === 'ObjectPattern'
+		&& node.parent.parent.properties.includes(node.parent)
+		&& isConstVariableDeclarationId(node.parent.parent)
+		&& isAwaitImportOrRequireFromIgnoredPackages(node.parent.parent.parent.init)
+	) {
+		return true;
+	}
+
+	// `const EventEmitter = (...).EventEmitter`
+	if (
+		isConstVariableDeclarationId(node)
+		&& isMemberExpression(node.parent.init, {property: 'EventEmitter', optional: false, computed: false})
+		&& isAwaitImportOrRequireFromIgnoredPackages(node.parent.init.object)
+	) {
+		return true;
+	}
+
+	return false;
+}
+
 /** @param {import('eslint').Rule.RuleContext} context */
-const create = () => ({
+const create = context => ({
 	Identifier(node) {
 		if (!(
 			node.name === 'EventEmitter'
@@ -21,6 +91,12 @@ const create = () => ({
 			return;
 		}
 
+		const scope = context.sourceCode.getScope(node);
+		const variableNode = findVariable(scope, node)?.defs[0]?.name;
+		if (isFromIgnoredPackage(variableNode)) {
+			return;
+		}
+
 		return {
 			node,
 			messageId: MESSAGE_ID,

rules/utils/get-ancestor.js

@@ -0,0 +1,20 @@
+'use strict';
+
+// TODO: Support more types
+function getPredicate(options) {
+	if (typeof options === 'string') {
+		return node => node.type === options;
+	}
+}
+
+function getAncestor(node, options) {
+	const predicate = getPredicate(options);
+
+	for (;node.parent; node = node.parent) {
+		if (predicate(node)) {
+			return node;
+		}
+	}
+}
+
+module.exports = getAncestor;

rules/utils/index.js

@@ -48,5 +48,6 @@ module.exports = {
 	shouldAddParenthesesToSpreadElementArgument: require('./should-add-parentheses-to-spread-element-argument.js'),
 	singular: require('./singular.js'),
 	toLocation: require('./to-location.js'),
+	getAncestor: require('./get-ancestor.js'),
 };
 

test/prefer-event-target.mjs

@@ -17,6 +17,24 @@ test.snapshot({
 		'const Foo = class EventEmitter extends Foo {}',
 		'new Foo(EventEmitter)',
 		'new foo.EventEmitter()',
+		...[
+			'import {EventEmitter} from "@angular/core";',
+			'const {EventEmitter} = require("@angular/core");',
+			'const EventEmitter = require("@angular/core").EventEmitter;',
+			'import {EventEmitter} from "eventemitter3";',
+			'const {EventEmitter} = await import("eventemitter3");',
+			'const EventEmitter = (await import("eventemitter3")).EventEmitter;',
+		].map(code => outdent`
+			${code}
+			class Foo extends EventEmitter {}
+		`),
+		'EventTarget()',
+		'new EventTarget',
+		'const target = new EventTarget;',
+		'const target = EventTarget()',
+		'const target = new Foo(EventEmitter);',
+		'EventEmitter()',
+		'const emitter = EventEmitter()',
 	],
 	invalid: [
 		'class Foo extends EventEmitter {}',
@@ -28,21 +46,10 @@ test.snapshot({
 				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;',
+		// For coverage
+		'for (const {EventEmitter} of []) {new EventEmitter}',
+		'for (const EventEmitter of []) {new EventEmitter}',
 	],
 });

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

@@ -50,7 +50,7 @@ Generated by [AVA](https://avajs.dev).
       4 | }␊
     `
 
-## Invalid #1
+## Invalid #5
       1 | new EventEmitter
 
 > Error 1/1
@@ -60,7 +60,7 @@ Generated by [AVA](https://avajs.dev).
         |     ^^^^^^^^^^^^ Prefer \`EventTarget\` over \`EventEmitter\`.␊
     `
 
-## Invalid #2
+## Invalid #6
       1 | const emitter = new EventEmitter;
 
 > Error 1/1
@@ -69,3 +69,23 @@ Generated by [AVA](https://avajs.dev).
     > 1 | const emitter = new EventEmitter;␊
         |                     ^^^^^^^^^^^^ Prefer \`EventTarget\` over \`EventEmitter\`.␊
     `
+
+## Invalid #7
+      1 | for (const {EventEmitter} of []) {new EventEmitter}
+
+> Error 1/1
+
+    `␊
+    > 1 | for (const {EventEmitter} of []) {new EventEmitter}␊
+        |                                       ^^^^^^^^^^^^ Prefer \`EventTarget\` over \`EventEmitter\`.␊
+    `
+
+## Invalid #8
+      1 | for (const EventEmitter of []) {new EventEmitter}
+
+> Error 1/1
+
+    `␊
+    > 1 | for (const EventEmitter of []) {new EventEmitter}␊
+        |                                     ^^^^^^^^^^^^ Prefer \`EventTarget\` over \`EventEmitter\`.␊
+    `