Prevent using arguments for generated variable names (#4613)

Author: lukastaegert

src/utils/identifierHelpers.ts

@@ -4,8 +4,11 @@ const illegalCharacters = /[^$_a-zA-Z0-9]/g;
 
 const startsWithDigit = (str: string): boolean => /\d/.test(str[0]);
 
+const needsEscape = (str: string) =>
+	startsWithDigit(str) || RESERVED_NAMES.has(str) || str === 'arguments';
+
 export function isLegal(str: string): boolean {
-	if (startsWithDigit(str) || RESERVED_NAMES.has(str)) {
+	if (needsEscape(str)) {
 		return false;
 	}
 	return !illegalCharacters.test(str);
@@ -14,7 +17,7 @@ export function isLegal(str: string): boolean {
 export function makeLegal(str: string): string {
 	str = str.replace(/-(\w)/g, (_, letter) => letter.toUpperCase()).replace(illegalCharacters, '_');
 
-	if (startsWithDigit(str) || RESERVED_NAMES.has(str)) str = `_${str}`;
+	if (needsEscape(str)) str = `_${str}`;
 
 	return str || '_';
 }

test/function/samples/escape-arguments/_config.js

@@ -0,0 +1,8 @@
+const assert = require('assert');
+
+module.exports = {
+	description: 'does not use "arguments" as a placeholder variable for a default export',
+	exports(exports) {
+		assert.deepStrictEqual(exports, { foo: { __proto__: null, default: 42 } });
+	}
+};

test/function/samples/escape-arguments/arguments.js

@@ -0,0 +1 @@
+export default 42;

test/function/samples/escape-arguments/main.js

@@ -0,0 +1 @@
+export * as foo from './arguments.js';