Add prefer-string-raw rule (#2339)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

docs/rules/prefer-string-raw.md

@@ -0,0 +1,30 @@
+# Prefer using the `String.raw` tag to avoid escaping `\`
+
+💼 This rule is enabled in the ✅ `recommended` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#preset-configs-eslintconfigjs).
+
+🔧 This rule is automatically fixable by the [`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix).
+
+<!-- end auto-generated rule header -->
+<!-- Do not manually modify this header. Run: `npm run fix:eslint-docs` -->
+
+[`String.raw`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/raw) can be used to avoid escaping `\`.
+
+## Fail
+
+```js
+const file = "C:\\windows\\style\\path\\to\\file.js";
+```
+
+```js
+const regexp = new RegExp('foo\\.bar');
+```
+
+## Pass
+
+```js
+const file = String.raw`C:\windows\style\path\to\file.js`;
+```
+
+```js
+const regexp = new RegExp(String.raw`foo\.bar`);
+```

package.json

@@ -124,7 +124,9 @@
 			"test/integration/{fixtures,fixtures-local}/**"
 		],
 		"rules": {
+			"unicorn/escape-case": "off",
 			"unicorn/expiring-todo-comments": "off",
+			"unicorn/no-hex-escape": "off",
 			"unicorn/no-null": "error",
 			"unicorn/prefer-array-flat": [
 				"error",

readme.md

@@ -207,6 +207,7 @@ If you don't use the preset, ensure you use the same `env` and `parserOptions` c
 | [prefer-set-has](docs/rules/prefer-set-has.md)                                                   | Prefer `Set#has()` over `Array#includes()` when checking for existence or non-existence.                                                                                                                          | ✅  | 🔧 | 💡 |
 | [prefer-set-size](docs/rules/prefer-set-size.md)                                                 | Prefer using `Set#size` instead of `Array#length`.                                                                                                                                                                | ✅  | 🔧 |    |
 | [prefer-spread](docs/rules/prefer-spread.md)                                                     | Prefer the spread operator over `Array.from(…)`, `Array#concat(…)`, `Array#{slice,toSpliced}()` and `String#split('')`.                                                                                           | ✅  | 🔧 | 💡 |
+| [prefer-string-raw](docs/rules/prefer-string-raw.md)                                             | Prefer using the `String.raw` tag to avoid escaping `\`.                                                                                                                                                          | ✅  | 🔧 |    |
 | [prefer-string-replace-all](docs/rules/prefer-string-replace-all.md)                             | Prefer `String#replaceAll()` over regex searches with the global flag.                                                                                                                                            | ✅  | 🔧 |    |
 | [prefer-string-slice](docs/rules/prefer-string-slice.md)                                         | Prefer `String#slice()` over `String#substr()` and `String#substring()`.                                                                                                                                          | ✅  | 🔧 |    |
 | [prefer-string-starts-ends-with](docs/rules/prefer-string-starts-ends-with.md)                   | Prefer `String#startsWith()` & `String#endsWith()` over `RegExp#test()`.                                                                                                                                          | ✅  | 🔧 | 💡 |

rules/ast/index.js

@@ -25,6 +25,7 @@ module.exports = {
 	isArrowFunctionBody: require('./is-arrow-function-body.js'),
 	isCallExpression,
 	isCallOrNewExpression,
+	isDirective: require('./is-directive.js'),
 	isEmptyNode: require('./is-empty-node.js'),
 	isExpressionStatement: require('./is-expression-statement.js'),
 	isFunction: require('./is-function.js'),

rules/ast/is-directive.js

@@ -0,0 +1,7 @@
+'use strict';
+
+const isDirective = node =>
+	node.type === 'ExpressionStatement'
+	&& typeof node.directive === 'string';
+
+module.exports = isDirective;

rules/no-empty-file.js

@@ -1,12 +1,11 @@
 'use strict';
-const {isEmptyNode} = require('./ast/index.js');
+const {isEmptyNode, isDirective} = require('./ast/index.js');
 
 const MESSAGE_ID = 'no-empty-file';
 const messages = {
 	[MESSAGE_ID]: 'Empty files are not allowed.',
 };
 
-const isDirective = node => node.type === 'ExpressionStatement' && typeof node.directive === 'string';
 const isEmpty = node => isEmptyNode(node, isDirective);
 
 const isTripleSlashDirective = node =>

rules/no-unnecessary-polyfills.js

@@ -23,13 +23,13 @@ const additionalPolyfillPatterns = {
 
 const prefixes = '(mdn-polyfills/|polyfill-)';
 const suffixes = '(-polyfill)';
-const delimiter = '(\\.|-|\\.prototype\\.|/)?';
+const delimiter = String.raw`(\.|-|\.prototype\.|/)?`;
 
 const polyfills = Object.keys(compatData).map(feature => {
 	let [ecmaVersion, constructorName, methodName = ''] = feature.split('.');
 
 	if (ecmaVersion === 'es') {
-		ecmaVersion = '(es\\d*)';
+		ecmaVersion = String.raw`(es\d*)`;
 	}
 
 	constructorName = `(${constructorName}|${camelCase(constructorName)})`;

rules/prefer-string-raw.js

@@ -0,0 +1,93 @@
+'use strict';
+const {isStringLiteral, isDirective} = require('./ast/index.js');
+const {fixSpaceAroundKeyword} = require('./fix/index.js');
+
+const MESSAGE_ID = 'prefer-string-raw';
+const messages = {
+	[MESSAGE_ID]: '`String.raw` should be used to avoid escaping `\\`.',
+};
+
+const BACKSLASH = '\\';
+
+function unescapeBackslash(raw) {
+	const quote = raw.charAt(0);
+
+	raw = raw.slice(1, -1);
+
+	let result = '';
+	for (let position = 0; position < raw.length; position++) {
+		const character = raw[position];
+		if (character === BACKSLASH) {
+			const nextCharacter = raw[position + 1];
+			if (nextCharacter === BACKSLASH || nextCharacter === quote) {
+				result += nextCharacter;
+				position++;
+				continue;
+			}
+		}
+
+		result += character;
+	}
+
+	return result;
+}
+
+/** @param {import('eslint').Rule.RuleContext} context */
+const create = context => {
+	context.on('Literal', node => {
+		if (
+			!isStringLiteral(node)
+			|| isDirective(node.parent)
+			|| (
+				(
+					node.parent.type === 'ImportDeclaration'
+						|| node.parent.type === 'ExportNamedDeclaration'
+						|| node.parent.type === 'ExportAllDeclaration'
+				) && node.parent.source === node
+			)
+			|| (node.parent.type === 'Property' && !node.parent.computed && node.parent.key === node)
+			|| (node.parent.type === 'JSXAttribute' && node.parent.value === node)
+		) {
+			return;
+		}
+
+		const {raw} = node;
+		if (
+			raw.at(-2) === BACKSLASH
+			|| !raw.includes(BACKSLASH + BACKSLASH)
+			|| raw.includes('`')
+			|| raw.includes('${')
+			|| node.loc.start.line !== node.loc.end.line
+		) {
+			return;
+		}
+
+		const unescaped = unescapeBackslash(raw);
+		if (unescaped !== node.value) {
+			return;
+		}
+
+		return {
+			node,
+			messageId: MESSAGE_ID,
+			* fix(fixer) {
+				yield fixer.replaceText(node, `String.raw\`${unescaped}\``);
+				yield * fixSpaceAroundKeyword(fixer, node, context.sourceCode);
+			},
+		};
+	});
+};
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+	create,
+	meta: {
+		type: 'suggestion',
+		docs: {
+			description: 'Prefer using the `String.raw` tag to avoid escaping `\\`.',
+			recommended: true,
+		},
+		fixable: 'code',
+		messages,
+	},
+};

rules/utils/escape-template-element-raw.js

@@ -2,6 +2,6 @@
 
 const escapeTemplateElementRaw = string => string.replaceAll(
 	/(?<=(?:^|[^\\])(?:\\\\)*)(?<symbol>(?:`|\$(?={)))/g,
-	'\\$<symbol>',
+	String.raw`\$<symbol>`,
 );
 module.exports = escapeTemplateElementRaw;