fix: empty URL should not provide the breadcrumb "undefined"

Author: isaacs

packages/core/src/utils/url.ts

@@ -319,7 +319,9 @@ export function getSanitizedUrlString(url: PartialURL): string {
       .replace(/(:80)$/, '')
       .replace(/(:443)$/, '') || '';
 
-  return `${protocol ? `${protocol}://` : ''}${filteredHost}${path}`;
+  // `parseUrl` returns `{}` for an empty or unparseable URL, and interpolating a missing path
+  // would render the string 'undefined'.
+  return `${protocol ? `${protocol}://` : ''}${filteredHost}${path || ''}`;
 }
 
 /**

packages/core/test/lib/integrations/fetch.test.ts

@@ -253,6 +253,23 @@ describe('createFetchIntegration', () => {
     expect(addBreadcrumbSpy.mock.lastCall?.[0].data?.['url.query']).toBeUndefined();
   });
 
+  it('records an empty breadcrumb URL rather than the string "undefined"', () => {
+    const handler = setupIntegration(fetchIntegration(), client);
+
+    handler({
+      fetchData: { url: '', method: 'GET' },
+      args: [''],
+      startTimestamp: Date.now(),
+      endTimestamp: Date.now() + 100,
+      error: new Error('Invalid URL'),
+    });
+
+    expect(addBreadcrumbSpy).toHaveBeenCalledWith(
+      expect.objectContaining({ data: { method: 'GET', url: '' } }),
+      expect.anything(),
+    );
+  });
+
   it('creates an error-level breadcrumb for a failed request', () => {
     const handler = setupIntegration(fetchIntegration(), client);
 

packages/core/test/lib/utils/url.test.ts

@@ -78,6 +78,8 @@ describe('getSanitizedUrlString', () => {
     ['url with port 4433', 'http://172.31.12.144:4433/test', 'http://172.31.12.144:4433/test'],
     ['url with port 443', 'http://172.31.12.144:443/test', 'http://172.31.12.144/test'],
     ['url with IP and port 80', 'http://172.31.12.144:80/test', 'http://172.31.12.144/test'],
+    ['empty url', '', ''],
+    ['unparseable url', '???', ''],
   ])('returns a sanitized URL for a %s', (_, rawUrl: string, sanitizedURL: string) => {
     const urlObject = parseUrl(rawUrl);
     expect(getSanitizedUrlString(urlObject)).toEqual(sanitizedURL);