feat(eslint-plugin): add new rule to disalllow anonymous functions as exports

Author: bryceosterhaus

projects/eslint-plugin/configs/general.js

@@ -101,6 +101,7 @@ const config = {
 		'@liferay/imports-first': 'error',
 		'@liferay/no-abbreviations': 'error',
 		'@liferay/no-absolute-import': 'error',
+		'@liferay/no-anonymous-exports': 'error',
 		'@liferay/no-duplicate-imports': 'error',
 		'@liferay/no-dynamic-require': 'error',
 		'@liferay/no-get-data-attribute': 'error',

projects/eslint-plugin/rules/general/docs/rules/no-anonymous-exports.md

@@ -0,0 +1,25 @@
+# Prefer exporting named functions (no-anonymous-exports)
+
+To improve debugging and readability, it is preferable to export named functions to that they can be located in a callstack.
+
+## Rule Details
+
+Examples of **incorrect** code for this rule:
+
+```js
+export const x = () => {};
+
+export default () => {};
+```
+
+Examples of **correct** code for this rule:
+
+```js
+export function x() {}
+
+export default function x() {}
+```
+
+## See also
+
+-   https://github.com/liferay/liferay-frontend-projects/issues/25

projects/eslint-plugin/rules/general/index.js

@@ -13,6 +13,7 @@ module.exports = {
 	'imports-first': require('./lib/rules/imports-first'),
 	'no-abbreviations': require('./lib/rules/no-abbreviations'),
 	'no-absolute-import': require('./lib/rules/no-absolute-import'),
+	'no-anonymous-exports': require('./lib/rules/no-anonymous-exports'),
 	'no-arrow': require('./lib/rules/no-arrow'),
 	'no-duplicate-class-names': require('./lib/rules/no-duplicate-class-names'),
 	'no-duplicate-imports': require('./lib/rules/no-duplicate-imports'),

projects/eslint-plugin/rules/general/lib/rules/no-anonymous-exports.js

@@ -0,0 +1,46 @@
+/**
+ * SPDX-FileCopyrightText: © 2021 Liferay, Inc. <https://liferay.com>
+ * SPDX-License-Identifier: MIT
+ */
+
+module.exports = {
+	create(context) {
+		return {
+			ExportDefaultDeclaration(node) {
+				if (
+					node.declaration &&
+					node.declaration.type === 'ArrowFunctionExpression'
+				) {
+					context.report({
+						message:
+							"Use named function for export. Example: 'function fooBar() {}'",
+						node,
+					});
+				}
+			},
+			ExportNamedDeclaration(node) {
+				if (
+					node.declaration &&
+					node.declaration.type === 'VariableDeclaration' &&
+					node.declaration.declarations &&
+					node.declaration.declarations[0] &&
+					node.declaration.declarations[0].init &&
+					node.declaration.declarations[0].init.type ===
+						'ArrowFunctionExpression'
+				) {
+					context.report({
+						message:
+							"Use named function for export instead of arrow function. Example: 'function fooBar() {}'",
+						node,
+					});
+				}
+			},
+		};
+	},
+	meta: {
+		category: 'Best Practices',
+		description: 'Prefer exporting named functions',
+		recommended: false,
+		url: 'https://github.com/liferay/liferay-frontend-projects/issues/25',
+	},
+};

projects/eslint-plugin/rules/general/tests/lib/rules/no-anonymous-exports.js

@@ -0,0 +1,49 @@
+/**
+ * SPDX-FileCopyrightText: © 2017 Liferay, Inc. <https://liferay.com>
+ * SPDX-License-Identifier: MIT
+ */
+
+const MultiTester = require('../../../../../scripts/MultiTester');
+const rule = require('../../../lib/rules/no-anonymous-exports');
+
+const parserOptions = {
+	parserOptions: {
+		ecmaVersion: 6,
+		sourceType: 'module',
+	},
+};
+
+const ruleTester = new MultiTester(parserOptions);
+
+ruleTester.run('no-anonymous-exports', rule, {
+	invalid: [
+		{
+			code: `export const test = () => {}`,
+			errors: [
+				{
+					message:
+						"Use named function for export instead of arrow function. Example: 'function fooBar() {}'",
+					type: 'ExportNamedDeclaration',
+				},
+			],
+		},
+		{
+			code: `export default () => {}`,
+			errors: [
+				{
+					message:
+						"Use named function for export. Example: 'function fooBar() {}'",
+					type: 'ExportDefaultDeclaration',
+				},
+			],
+		},
+	],
+	valid: [
+		{
+			code: `
+				export function test() {}
+				export default function fooBar() {}
+			`,
+		},
+	],
+});