Add test for already correctly escaped slashes and improve escaping logic

Co-authored-by: mrlubos <[email protected]>

Author: Copilot

packages/openapi-ts/src/tsc/__tests__/types.test.ts

@@ -63,4 +63,14 @@ describe('createRegularExpressionLiteral', () => {
 
     expect(result.text).toBe('//');
   });
+
+  it('should handle patterns with already correctly escaped slashes', () => {
+    const result = createRegularExpressionLiteral({
+      text: '^data:image\\/svg\\+xml;base64,[A-Za-z0-9+\\/]+=*$',
+    });
+
+    expect(result.text).toBe(
+      '/^data:image\\/svg\\+xml;base64,[A-Za-z0-9+\\/]+=*$/',
+    );
+  });
 });

packages/openapi-ts/src/tsc/types.ts

@@ -1084,8 +1084,8 @@ export const createRegularExpressionLiteral = ({
   const patternContent =
     text.startsWith('/') && text.endsWith('/') ? text.slice(1, -1) : text;
 
-  // Escape forward slashes in the pattern content
-  const escapedPattern = patternContent.replace(/\//g, '\\/');
+  // Escape forward slashes in the pattern content, but only if they're not already escaped
+  const escapedPattern = patternContent.replace(/(?<!\\)\//g, '\\/');
 
   // Wrap with forward slashes
   const textWithSlashes = `/${escapedPattern}/`;