Add escape-case rule - fixes #54 (#63)

Author: Bebersohl

docs/rules/escape-case.md

@@ -0,0 +1,23 @@
+# Require escape sequences to use uppercase values
+
+Enforces defining escape sequence values with uppercase characters rather than lowercase ones. This promotes readability by making the escaped value more distinguishable from the identifier.
+
+
+## Fail
+
+```js
+const foo = '\xa9';
+const foo = '\ud834';
+const foo = '\u{1d306}';
+const foo = '\ca';
+```
+
+
+## Pass
+
+```js
+const foo = '\xA9';
+const foo = '\uD834';
+const foo = '\u{1D306}';
+const foo = '\cA';
+```

index.js

@@ -20,6 +20,7 @@ module.exports = {
 				'unicorn/no-process-exit': 'error',
 				'unicorn/throw-new-error': 'error',
 				'unicorn/number-literal-case': 'error',
+				'unicorn/escape-case': 'error',
 				'unicorn/no-array-instanceof': 'error',
 				'unicorn/no-new-buffer': 'error',
 				'unicorn/no-hex-escape': 'error'

readme.md

@@ -40,6 +40,7 @@ Configure it in `package.json`.
 			"unicorn/no-process-exit": "error",
 			"unicorn/throw-new-error": "error",
 			"unicorn/number-literal-case": "error",
+			"unicorn/escape-case": "error",
 			"unicorn/no-array-instanceof": "error",
 			"unicorn/no-new-buffer": "error",
 			"unicorn/no-hex-escape": "error"
@@ -58,6 +59,7 @@ Configure it in `package.json`.
 - [no-process-exit](docs/rules/no-process-exit.md) - Disallow `process.exit()`.
 - [throw-new-error](docs/rules/throw-new-error.md) - Require `new` when throwing an error. *(fixable)*
 - [number-literal-case](docs/rules/number-literal-case.md) - Enforce lowercase identifier and uppercase value for number literals. *(fixable)*
+- [escape-case](docs/rules/escape-case.md) - Require escape sequences to use uppercase values. *(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)*

rules/escape-case.js

@@ -0,0 +1,44 @@
+'use strict';
+const escapeWithLowercase = /\\(x[a-f0-9]{2}|u[a-f0-9]{4}|u\{([0-9a-f]{1,})\}|c[a-z])/;
+const message = 'Use uppercase characters for the value of the escape sequence.';
+
+const fix = value => {
+	const results = escapeWithLowercase.exec(value);
+
+	if (results) {
+		const fixedEscape = results[0].slice(0, 2) + results[0].slice(2).toUpperCase();
+		return value.slice(0, results.index) + fixedEscape + value.slice(results.index + results[0].length);
+	}
+
+	return value;
+};
+
+const create = context => {
+	return {
+		Literal(node) {
+			if (typeof node.value === 'string' && node.raw.match(escapeWithLowercase)) {
+				context.report({
+					node,
+					message,
+					fix: fixer => fixer.replaceTextRange([node.start, node.end], fix(node.raw))
+				});
+			}
+		},
+		TemplateElement(node) {
+			if (typeof node.value.raw === 'string' && node.value.raw.match(escapeWithLowercase)) {
+				context.report({
+					node,
+					message,
+					fix: fixer => fixer.replaceTextRange([node.start, node.end], fix(node.value.raw))
+				});
+			}
+		}
+	};
+};
+
+module.exports = {
+	create,
+	meta: {
+		fixable: 'code'
+	}
+};

test/escape-case.js

@@ -0,0 +1,112 @@
+/* eslint-disable no-template-curly-in-string */
+import test from 'ava';
+import avaRuleTester from 'eslint-ava-rule-tester';
+import rule from '../rules/escape-case';
+
+const ruleTester = avaRuleTester(test, {
+	env: {
+		es6: true
+	}
+});
+
+const errors = [{
+	ruleId: 'escape-case',
+	message: 'Use uppercase characters for the value of the escape sequence.'
+}];
+
+ruleTester.run('escape-case', rule, {
+	valid: [
+		'const foo = "\\xA9";',
+		'const foo = "\\uD834";',
+		'const foo = "\\u{1D306}";',
+		'const foo = "\\cA";',
+		'const foo = `\\xA9`;',
+		'const foo = `\\uD834`;',
+		'const foo = `\\u{1D306}`;',
+		'const foo = `\\cA`;',
+		'const foo = `\\uD834foo`;',
+		'const foo = `foo\\uD834`;',
+		'const foo = `foo \\uD834`;',
+		'const foo = `${"\uD834 foo"} \\uD834`;',
+		'const foo = "\\uD834foo";',
+		'const foo = "foo\\uD834";',
+		'const foo = "foo \\uD834";'
+	],
+	invalid: [
+		{
+			code: 'const foo = "\\xa9";',
+			errors,
+			output: 'const foo = "\\xA9";'
+		},
+		{
+			code: 'const foo = "\\ud834";',
+			errors,
+			output: 'const foo = "\\uD834";'
+		},
+		{
+			code: 'const foo = "\\u{1d306}";',
+			errors,
+			output: 'const foo = "\\u{1D306}";'
+		},
+		{
+			code: 'const foo = "\\ca";',
+			errors,
+			output: 'const foo = "\\cA";'
+		},
+		{
+			code: 'const foo = `\\xa9`;',
+			errors,
+			output: 'const foo = `\\xA9`;'
+		},
+		{
+			code: 'const foo = `\\ud834`;',
+			errors,
+			output: 'const foo = `\\uD834`;'
+		},
+		{
+			code: 'const foo = `\\u{1d306}`;',
+			errors,
+			output: 'const foo = `\\u{1D306}`;'
+		},
+		{
+			code: 'const foo = `\\ca`;',
+			errors,
+			output: 'const foo = `\\cA`;'
+		},
+		{
+			code: 'const foo = `\\ud834foo`;',
+			errors,
+			output: 'const foo = `\\uD834foo`;'
+		},
+		{
+			code: 'const foo = `foo\\ud834`;',
+			errors,
+			output: 'const foo = `foo\\uD834`;'
+		},
+		{
+			code: 'const foo = `foo \\ud834`;',
+			errors,
+			output: 'const foo = `foo \\uD834`;'
+		},
+		{
+			code: 'const foo = `${"\ud834 foo"} \\ud834`;',
+			errors,
+			output: 'const foo = `${"\uD834 foo"} \\uD834`;'
+		},
+		{
+			code: 'const foo = "\\ud834foo";',
+			errors,
+			output: 'const foo = "\\uD834foo";'
+		},
+		{
+			code: 'const foo = "foo\\ud834";',
+			errors,
+			output: 'const foo = "foo\\uD834";'
+		},
+		{
+			code: 'const foo = "foo \\ud834";',
+			errors,
+			output: 'const foo = "foo \\uD834";'
+		}
+	]
+});