JS-1321 Fix S101 false positive: allow $ prefix in default naming convention (#6484)

Co-authored-by: Vibe Bot <vibe-bot@sonarsource.com>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>
Co-authored-by: Francois Mora <francois.mora@sonarsource.com>

Author: 4 people

packages/jsts/src/rules/S101/config.ts

@@ -23,7 +23,8 @@ export const fields = [
     {
       field: 'format',
       description: 'Regular expression used to check the class names against.',
-      default: '^[A-Z][a-zA-Z0-9]*$',
+      default: String.raw`^\$?[A-Z][a-zA-Z0-9]*$`,
+      customDefault: String.raw`^\\$?[A-Z][a-zA-Z0-9]*$`,
     },
   ],
 ] as const satisfies ESLintConfiguration;

packages/jsts/src/rules/S101/rule.ts

@@ -25,7 +25,7 @@ import * as meta from './generated-meta.js';
 
 type ClassOrInterfaceDeclaration = TSESTree.ClassDeclaration | TSESTree.TSInterfaceDeclaration;
 
-const DEFAULT_FORMAT = '^[A-Z][a-zA-Z0-9]*$';
+const DEFAULT_FORMAT = String.raw`^\$?[A-Z][a-zA-Z0-9]*$`;
 const messages = {
   renameClass: 'Rename {{symbolType}} "{{symbol}}" to match the regular expression {{format}}.',
 };

packages/jsts/src/rules/S101/unit.test.ts

@@ -20,7 +20,7 @@ import { describe, it } from 'node:test';
 
 const ruleTester = new NoTypeCheckingRuleTester();
 
-const DEFAULT_FORMAT = '^[A-Z][a-zA-Z0-9]*$';
+const DEFAULT_FORMAT = '^\\$?[A-Z][a-zA-Z0-9]*$';
 const CUSTOM_FORMAT = '^[_A-Z][a-zA-Z0-9]*$';
 
 describe('S101', () => {
@@ -30,7 +30,7 @@ describe('S101', () => {
         {
           code: `
       class MyClass {}
-      var x = class y {} // Compliant, rule doesn't check class expressions
+      var x = class y {} // Compliant: expressions not checked
       interface MyInterface {}
       `,
           options: [{ format: DEFAULT_FORMAT }],
@@ -43,6 +43,22 @@ describe('S101', () => {
       `,
           options: [{ format: CUSTOM_FORMAT }],
         },
+        {
+          // Compliant: $ prefix allowed by default
+          code: `
+      interface $ZodCheckDef {}
+      interface $ZodCheckInternals<T> {}
+      interface $ZodCheckLessThanDef extends $ZodCheckDef {}
+      interface $ZodCheckLessThanInternals<T extends number> extends $ZodCheckInternals<T> {}
+      `,
+        },
+        {
+          // Compliant: $ prefix allowed by default
+          code: `
+      class $LocationShimProvider {}
+      class $ServiceProvider {}
+      `,
+        },
       ],
       invalid: [
         {
@@ -67,6 +83,14 @@ describe('S101', () => {
             },
           ],
         },
+        {
+          code: `interface $my_interface {}`, // $ before snake_case still flagged
+          errors: [
+            {
+              message: `Rename interface "$my_interface" to match the regular expression ${DEFAULT_FORMAT}.`,
+            },
+          ],
+        },
         {
           code: `class __MyClass {}`,
           options: [{ format: CUSTOM_FORMAT }],