feat(eslint-plugin): add new rule to disallow 'use strict' in es modules

maintenance/projects/senna/.eslintrc.js

@@ -12,6 +12,7 @@ module.exports = {
 	rules: {
 		'@liferay/no-abbreviations': 'off',
 		'@liferay/no-it-should': 'warn',
+		'@liferay/no-use-strict-in-module': 'off',
 		'curly': 'warn',
 		'default-case': 'warn',
 		'no-console': 'warn',

projects/eslint-plugin/configs/general.js

@@ -101,12 +101,14 @@ 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',
 		'@liferay/no-it-should': 'error',
 		'@liferay/no-length-jsx-expression': 'error',
 		'@liferay/no-require-and-call': 'error',
+		'@liferay/no-use-strict-in-module': 'error',
 		'@liferay/padded-test-blocks': 'error',
 		'@liferay/ref-name-suffix': 'error',
 		'@liferay/sort-import-destructures': '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/docs/rules/no-use-strict-in-module.md

@@ -0,0 +1,40 @@
+# Disallow 'use strict' in es modules (no-use-strict-in-module)
+
+You never need `'use strict'` in an ES module ([spec](http://www.ecma-international.org/ecma-262/6.0/#sec-strict-mode-code)). We can infer if file is an esmodule if it uses export/import syntax.
+
+## Rule Details
+
+Examples of **incorrect** code for this rule:
+
+```js
+'use strict';
+
+export default () => {};
+```
+
+```js
+'use strict';
+
+import foo from 'bar';
+```
+
+Examples of **correct** code for this rule:
+
+```js
+import foo from 'bar';
+//...
+```
+
+```js
+//...
+export default foo;
+```
+
+```js
+//...
+export foo;
+```
+
+## Further Reading
+
+-   [Initial motivation for this rule](https://github.com/liferay/liferay-frontend-projects/issues/20).

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'),
@@ -21,6 +22,7 @@ module.exports = {
 	'no-it-should': require('./lib/rules/no-it-should'),
 	'no-length-jsx-expression': require('./lib/rules/no-length-jsx-expression'),
 	'no-require-and-call': require('./lib/rules/no-require-and-call'),
+	'no-use-strict-in-module': require('./lib/rules/no-use-strict-in-module'),
 	'padded-test-blocks': require('./lib/rules/padded-test-blocks'),
 	'ref-name-suffix': require('./lib/rules/ref-name-suffix'),
 	'sort-class-names': require('./lib/rules/sort-class-names'),

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/lib/rules/no-use-strict-in-module.js

@@ -0,0 +1,57 @@
+/**
+ * SPDX-FileCopyrightText: © 2021 Liferay, Inc. <https://liferay.com>
+ * SPDX-License-Identifier: MIT
+ */
+
+const message = `'use strict' is unnecessary inside of modules`;
+
+module.exports = {
+	create(context) {
+		const useStrictExpressions = [];
+		let esModule;
+
+		const checkEsModule = () => {
+			if (!esModule) {
+				esModule = true;
+			}
+		};
+
+		return {
+			'ExportDefaultDeclaration': checkEsModule,
+			'ExportNamedDeclaration': checkEsModule,
+			'ExpressionStatement'(node) {
+				if (
+					node.expression.type === 'Literal' &&
+					node.expression.value === 'use strict'
+				) {
+					useStrictExpressions.push(node.expression);
+				}
+			},
+			'ImportDeclaration': checkEsModule,
+			'ImportNamespaceSpecifier': checkEsModule,
+			'Program:exit': () => {
+				if (esModule) {
+					useStrictExpressions.forEach((expression) => {
+						context.report({
+							message,
+							node: expression,
+						});
+					});
+				}
+			},
+		};
+	},
+
+	meta: {
+		docs: {
+			category: 'Best Practices',
+			description: message,
+			recommended: false,
+			url:
+				'https://github.com/liferay/liferay-frontend-projects/issues/20',
+		},
+		fixable: 'code',
+		schema: [],
+		type: 'problem',
+	},
+};

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() {}
+			`,
+		},
+	],
+});

projects/eslint-plugin/rules/general/tests/lib/rules/no-use-strict-in-module.js

@@ -0,0 +1,92 @@
+/**
+ * SPDX-FileCopyrightText: © 2017 Liferay, Inc. <https://liferay.com>
+ * SPDX-License-Identifier: MIT
+ */
+
+const MultiTester = require('../../../../../scripts/MultiTester');
+const rule = require('../../../lib/rules/no-use-strict-in-module');
+
+const parserOptions = {
+	parserOptions: {
+		ecmaVersion: 6,
+		sourceType: 'module',
+	},
+};
+
+const ruleTester = new MultiTester(parserOptions);
+
+ruleTester.run('no-use-strict-in-module', rule, {
+	invalid: [
+		{
+			code: `
+				'use strict'
+
+				import {test} from 'test';
+			 `,
+			errors: [
+				{
+					message: `'use strict' is unnecessary inside of modules`,
+					type: 'Literal',
+				},
+			],
+		},
+		{
+			code: `
+				'use strict'
+
+				function test() {
+					'use strict'
+
+					return 'test';
+				}
+				export default test;
+			 `,
+			errors: [
+				{
+					message: `'use strict' is unnecessary inside of modules`,
+					type: 'Literal',
+				},
+				{
+					message: `'use strict' is unnecessary inside of modules`,
+					type: 'Literal',
+				},
+			],
+		},
+		{
+			code: `
+				'use strict'
+
+				function test() {}
+				export {test};
+			 `,
+			errors: [
+				{
+					message: `'use strict' is unnecessary inside of modules`,
+					type: 'Literal',
+				},
+			],
+		},
+	],
+
+	valid: [
+		{
+			code: `
+				import {test} from 'test';
+			 `,
+		},
+		{
+			code: `
+				'use strict'
+
+				module.export = function test() {}
+			 `,
+		},
+		{
+			code: `
+				'use strict'
+
+				console.log('foo');
+			 `,
+		},
+	],
+});

projects/js-toolkit/packages/dev-server/src/reload.ts

@@ -46,9 +46,9 @@ function setupLiveSession(): void {
 const CLOSE_BODY_TAG = '</body>';
 const RELOAD_SNIPPET = `<script>(${setupLiveSession.toString()})();</script>`;
 
-export default (content: string): string => {
+export default function (content: string): string {
 	return content.replace(
 		CLOSE_BODY_TAG,
 		`${RELOAD_SNIPPET}${CLOSE_BODY_TAG}`
 	);
-};
+}