Add no-hex-escape rule - fixes #51 (#62)

Author: matijs

docs/rules/no-hex-escape.md

@@ -0,0 +1,19 @@
+# Enforce the use of unicode escapes instead of hexadecimal escapes
+
+Enforces a convention of using [unicode escapes](https://mathiasbynens.be/notes/javascript-escapes#unicode) instead of [hexadecimal escapes](https://mathiasbynens.be/notes/javascript-escapes#hexadecimal) for consistency and clarity.
+
+
+## Fail
+
+```js
+const foo = '\x1B';
+const foo = `\x1B${bar}`;
+```
+
+
+## Pass
+
+```js
+const foo = '\u001B';
+const foo = `\u001B${bar}`;
+```

index.js

@@ -21,7 +21,8 @@ module.exports = {
 				'unicorn/throw-new-error': 'error',
 				'unicorn/number-literal-case': 'error',
 				'unicorn/no-array-instanceof': 'error',
-				'unicorn/no-new-buffer': 'error'
+				'unicorn/no-new-buffer': 'error',
+				'unicorn/no-hex-escape': 'error'
 			}
 		}
 	}

readme.md

@@ -59,6 +59,7 @@ Configure it in `package.json`.
 - [number-literal-case](docs/rules/number-literal-case.md) - Enforce lowercase identifier and uppercase value for number literals. *(fixable)*
 - [no-array-instanceof](docs/rules/no-array-instanceof.md) - Require `Array.isArray()` instead of `instanceof Array`. *(fixable)*
 - [no-new-buffer](docs/rules/no-new-buffer.md) - Enforce the use of `Buffer.from()` and `Buffer.alloc()` instead of the deprecated `new Buffer()`. *(fixable)*
+- [no-hex-escape](docs/rules/no-hex-escape.md) - Enforce the use of unicode escapes instead of hexadecimal escapes. *(fixable)*
 
 
 ## Recommended config

rules/no-hex-escape.js

@@ -0,0 +1,31 @@
+'use strict';
+
+function checkEscape(context, node, value) {
+	const fixedValue = typeof value === 'string' ? value.replace(/\\x/g, '\\u00') : value;
+
+	if (value !== fixedValue) {
+		context.report({
+			node,
+			message: 'Use unicode escapes instead of hexadecimal escapes.',
+			fix: fixer => fixer.replaceTextRange([node.start, node.end], fixedValue)
+		});
+	}
+}
+
+const create = context => {
+	return {
+		Literal: node => {
+			checkEscape(context, node, node.raw);
+		},
+		TemplateElement: node => {
+			checkEscape(context, node, node.value.raw);
+		}
+	};
+};
+
+module.exports = {
+	create,
+	meta: {
+		fixable: 'code'
+	}
+};

test/no-hex-escape.js

@@ -0,0 +1,106 @@
+import test from 'ava';
+import avaRuleTester from 'eslint-ava-rule-tester';
+import rule from '../rules/no-hex-escape';
+
+const ruleTester = avaRuleTester(test, {
+	env: {
+		es6: true
+	}
+});
+
+const error = {
+	ruleId: 'no-hex-escape',
+	message: 'Use unicode escapes instead of hexadecimal escapes.'
+};
+
+ruleTester.run('no-hex-escape', rule, {
+	valid: [
+		`const foo = 'foo'`,
+		`const foo = '\\u00b1'`,
+		`const foo = '\\u00b1\\u00b1'`,
+		`const foo = 'foo\\u00b1'`,
+		`const foo = 'foo\\u00b1foo'`,
+		`const foo = '\\u00b1foo'`,
+		'const foo = 42',
+		'const foo = `foo`',
+		'const foo = `\\u00b1`',
+		'const foo = `\\u00b1\\u00b1`',
+		'const foo = `foo\\u00b1`',
+		'const foo = `foo\\u00b1foo`',
+		'const foo = `\\u00b1foo`',
+		'const foo = `42`'
+	],
+	invalid: [
+		{
+			code: `const foo = '\\xb1'`,
+			errors: [error],
+			output: `const foo = '\\u00b1'`
+		},
+		{
+			code: `const foo = '\\xb1\\xb1'`,
+			errors: [error],
+			output: `const foo = '\\u00b1\\u00b1'`
+		},
+		{
+			code: `const foo = '\\xb1foo'`,
+			errors: [error],
+			output: `const foo = '\\u00b1foo'`
+		},
+		{
+			code: `const foo = '\\xd8\\x3d\\xdc\\xa9'`,
+			errors: [error],
+			output: `const foo = '\\u00d8\\u003d\\u00dc\\u00a9'`
+		},
+		{
+			code: `const foo = 'foo\\xb1'`,
+			errors: [error],
+			output: `const foo = 'foo\\u00b1'`
+		},
+		{
+			code: `const foo = 'foo\\x12foo\\x34'`,
+			errors: [error],
+			output: `const foo = 'foo\\u0012foo\\u0034'`
+		},
+		{
+			code: `const foo = '42\\x1242\\x34'`,
+			errors: [error],
+			output: `const foo = '42\\u001242\\u0034'`
+		},
+		// Test template literals
+		{
+			code: 'const foo = `\\xb1`',
+			errors: [error],
+			output: 'const foo = `\\u00b1`'
+		},
+		{
+			code: 'const foo = `\\xb1\\xb1`',
+			errors: [error],
+			output: 'const foo = `\\u00b1\\u00b1`'
+		},
+		{
+			code: 'const foo = `\\xb1foo`',
+			errors: [error],
+			output: 'const foo = `\\u00b1foo`'
+		},
+		{
+			code: 'const foo = `\\xd8\\x3d\\xdc\\xa9`',
+			errors: [error],
+			output: 'const foo = `\\u00d8\\u003d\\u00dc\\u00a9`'
+		},
+		{
+			code: 'const foo = `foo\\xb1`',
+			errors: [error],
+			output: 'const foo = `foo\\u00b1`'
+		},
+		{
+			code: 'const foo = `foo\\x12foo\\x34`',
+			errors: [error],
+			output: 'const foo = `foo\\u0012foo\\u0034`'
+		},
+		{
+			code: 'const foo = `42\\x1242\\x34`',
+			errors: [error],
+			output: 'const foo = `42\\u001242\\u0034`'
+		}
+	]
+});