convert undici node 18 string headers to array to dedupe and then back to string

Author: Lms24

dev-packages/node-integration-tests/suites/tracing/double-baggage-no-spans/test.ts

@@ -45,6 +45,7 @@ describe('double baggage prevention', () => {
       const [SERVER_URL, closeTestServer] = await createTestServer()
         .get('/api/fetch-custom-headers', headers => {
           // fetch with manual getTraceData() headers
+          // console.log('xx sentry-tace', headers['sentry-trace']);
           expect(headers['sentry-trace']).toEqual(expect.stringMatching(/^[a-f\d]{32}-[a-f\d]{16}$/));
           expectNoDuplicateSentryBaggageKeys(headers['baggage']);
           expectConsistentTraceId(headers);

dev-packages/node-integration-tests/suites/tracing/double-baggage-spans-parent/test.ts

@@ -49,13 +49,13 @@ describe('double baggage prevention - http.client spans with parent span', () =>
       const [SERVER_URL, closeTestServer] = await createTestServer()
         .get('/api/fetch-custom-headers', headers => {
           // fetch with manual getTraceData() headers — core reproduction case
+          const sentryTrace = extractTraceparentData(headers['sentry-trace'] as string);
+          transactionTraceId = sentryTrace!.traceId!;
+          fetchCustomHeadersSpanId = sentryTrace!.parentSpanId!;
           expectNoDuplicateSentryBaggageKeys(headers['baggage']);
           expect(headers['sentry-trace']).not.toContain(',');
           expectConsistentTraceId(headers);
           expectUserSetTraceId(headers);
-          const sentryTrace = extractTraceparentData(headers['sentry-trace'] as string);
-          transactionTraceId = sentryTrace!.traceId!;
-          fetchCustomHeadersSpanId = sentryTrace!.parentSpanId!;
         })
         .get('/api/fetch', headers => {
           // fetch without manual headers (baseline)

packages/node-core/src/utils/outgoingFetchRequest.ts

@@ -121,7 +121,29 @@ function _deduplicateHeaders(request: UndiciRequest): void {
   if (Array.isArray(request.headers)) {
     _deduplicateArrayHeaders(request.headers);
   } else {
-    request.headers = _deduplicateStringHeaders(request.headers);
+    const headersArray = request.headers.split('\r\n');
+    const headers: string[] = [];
+    for (const header of headersArray) {
+      try {
+        const [key, value] = header.split(':').map(part => part.trim());
+        if (key != null && value != null) {
+          headers.push(key, value);
+        }
+      } catch {
+        continue;
+      }
+    }
+
+    _deduplicateArrayHeaders(headers);
+
+    const headerPairs: string[] = [];
+    for (let i = 0; i < headers.length; i += 2) {
+      headerPairs.push(`${headers[i]}: ${headers[i + 1]}`);
+    }
+    const concatenated = headerPairs.join('\r\n');
+    if (concatenated) {
+      request.headers = concatenated.concat('\r\n');
+    }
   }
 }
 
@@ -161,31 +183,6 @@ function _deduplicateArrayHeader(headers: string[], headerName: string): void {
   }
 }
 
-function _deduplicateStringHeaders(input: string): string {
-  // Deduplicate sentry-trace — keep only the first occurrence
-  let sentryTraceCount = 0;
-  let result = input.replace(/sentry-trace: .*\r\n/g, match => {
-    return ++sentryTraceCount === 1 ? match : '';
-  });
-
-  // Deduplicate baggage — merge all occurrences into one but preserve initial sentry- values
-  let mergedBaggage: string | undefined;
-  result = result.replace(/baggage: (.*)\r\n/g, (_match, value: string) => {
-    if (!mergedBaggage) {
-      mergedBaggage = value;
-    } else {
-      mergedBaggage = mergeBaggageHeaders(value, mergedBaggage) || mergedBaggage;
-    }
-    return '';
-  });
-
-  if (mergedBaggage) {
-    result += `${SENTRY_BAGGAGE_HEADER}: ${mergedBaggage}\r\n`;
-  }
-
-  return result;
-}
-
 /** Add a breadcrumb for an outgoing fetch/undici request. */
 export function addFetchRequestBreadcrumb(request: UndiciRequest, response: UndiciResponse): void {
   const data = getBreadcrumbData(request);

packages/node-core/test/utils/outgoingFetchRequest.test.ts

@@ -304,5 +304,26 @@ describe('addTracePropagationHeadersToFetchRequest', () => {
         );
       });
     });
+
+    it("doesn't dedupe nearly-sentry-tracing headers", () => {
+      const request = {
+        headers:
+          'sentry-trace: user-trace_id-xyz-1\r\n' +
+          'baggage: sentry-trace_id=user-trace_id,sentry-sampled=true,sentry-environment=user\r\n' +
+          'x-sentry-trace: custom-trace_id-abc-1\r\n' +
+          'x-baggage: sentry-trace_id=undici-trace_id-abc-1,sentry-sampled=true,sentry-environment=undici\r\n',
+        origin: 'https://some-service.com',
+        path: '/api/test',
+      } as UndiciRequest;
+
+      addTracePropagationHeadersToFetchRequest(request, new LRUMap<string, boolean>(100));
+
+      expect(request.headers).toBe(
+        'sentry-trace: user-trace_id-xyz-1\r\n' +
+          'baggage: sentry-trace_id=user-trace_id,sentry-sampled=true,sentry-environment=user\r\n' +
+          'x-sentry-trace: custom-trace_id-abc-1\r\n' +
+          'x-baggage: sentry-trace_id=undici-trace_id-abc-1,sentry-sampled=true,sentry-environment=undici\r\n',
+      );
+    });
   });
 });