Add new-regexp rule - fixes #92 (#100)

docs/rules/new-regexp.md

@@ -0,0 +1,17 @@
+# Enforce the use of `new RegExp()` instead of `RegExp()`
+
+They work the same, but `new RegExp()` should be preferred for consistency with other constructors.
+
+
+## Fail
+
+```js
+const regexp = RegExp('foo');
+```
+
+
+## Pass
+
+```js
+const regexp = new RegExp('foo');
+```

index.js

@@ -28,7 +28,8 @@ module.exports = {
 				'unicorn/custom-error-definition': 'error',
 				'unicorn/prefer-starts-ends-with': 'error',
 				'unicorn/prefer-type-error': 'error',
-				'unicorn/no-fn-reference-in-iterator': 'error'
+				'unicorn/no-fn-reference-in-iterator': 'error',
+				'unicorn/new-regexp': 'error'
 			}
 		}
 	}

readme.md

@@ -46,7 +46,8 @@ Configure it in `package.json`.
 			"unicorn/no-hex-escape": "error",
 			"unicorn/custom-error-definition": "error",
 			"unicorn/prefer-starts-ends-with": "error",
-			"unicorn/prefer-type-error": "error"
+			"unicorn/prefer-type-error": "error",
+			"unicorn/new-regexp": "error"
 		}
 	}
 }
@@ -70,6 +71,7 @@ Configure it in `package.json`.
 - [prefer-starts-ends-with](docs/rules/prefer-starts-ends-with.md) - Prefer `String#startsWith` & `String#endsWith` over more complex alternatives.
 - [prefer-type-error](docs/rules/prefer-type-error.md) - Enforce throwing `TypeError` in type checking conditions. *(fixable)*
 - [no-fn-reference-in-iterator](docs/rules/no-fn-reference-in-iterator.md) - Prevents passing a function reference directly to iterator methods. *(fixable)*
+- [new-regexp](docs/rules/new-regexp.md) - Enforce the use of `new RegExp()` instead of `RegExp()`. *(fixable)*
 
 
 ## Recommended config

rules/new-regexp.js

@@ -0,0 +1,19 @@
+'use strict';
+const create = context => {
+	return {
+		'CallExpression[callee.name="RegExp"]': node => {
+			context.report({
+				node,
+				message: 'Use `new RegExp()` instead of `RegExp()`',
+				fix: fixer => fixer.insertTextBefore(node, 'new ')
+			});
+		}
+	};
+};
+
+module.exports = {
+	create,
+	meta: {
+		fixable: 'code'
+	}
+};

test/new-regexp.js

@@ -0,0 +1,45 @@
+import test from 'ava';
+import avaRuleTester from 'eslint-ava-rule-tester';
+import rule from '../rules/new-regexp';
+
+const ruleTester = avaRuleTester(test, {
+	env: {
+		es6: true
+	}
+});
+
+const error = {
+	ruleId: 'new-regexp',
+	message: 'Use `new RegExp()` instead of `RegExp()`'
+};
+
+ruleTester.run('new-regexp', rule, {
+	valid: [
+		`const foo = new RegExp('foo', 'g')`,
+		`const foo = new RegExp('foo')`,
+		`const foo = new RegExp(/foo/, 'g')`,
+		`new RegExp('foo', 'g').exec('foo')`
+	],
+	invalid: [
+		{
+			code: `const foo = RegExp('foo', 'g')`,
+			errors: [error],
+			output: `const foo = new RegExp('foo', 'g')`
+		},
+		{
+			code: `const foo = RegExp('foo')`,
+			errors: [error],
+			output: `const foo = new RegExp('foo')`
+		},
+		{
+			code: `const foo = RegExp(/foo/, 'g')`,
+			errors: [error],
+			output: `const foo = new RegExp(/foo/, 'g')`
+		},
+		{
+			code: `RegExp('foo', 'g').exec('foo')`,
+			errors: [error],
+			output: `new RegExp('foo', 'g').exec('foo')`
+		}
+	]
+});