feat: add W3C header support to tracing client and utils

Author: hangy

dart/lib/src/http_client/tracing_client.dart

@@ -50,6 +50,7 @@ class TracingClient extends BaseClient {
           _hub.options.tracePropagationTargets, request.url.toString())) {
         if (span != null) {
           addSentryTraceHeaderFromSpan(span, request.headers);
+          addW3CHeaderFromSpan(span, request.headers);
           addBaggageHeaderFromSpan(
             span,
             request.headers,
@@ -61,6 +62,7 @@ class TracingClient extends BaseClient {
 
           final traceHeader = propagationContext.toSentryTrace();
           addSentryTraceHeader(traceHeader, request.headers);
+          addW3CHeaderFromSentryTrace(traceHeader, request.headers);
 
           final baggage = propagationContext.baggage;
           if (baggage != null) {

dart/lib/src/utils/tracing_utils.dart

@@ -11,6 +11,22 @@ void addSentryTraceHeader(
   headers[traceHeader.name] = traceHeader.value;
 }
 
+void addW3CHeaderFromSpan(ISentrySpan span, Map<String, dynamic> headers) {
+  final traceHeader = span.toSentryTrace();
+  addW3CHeaderFromSentryTrace(traceHeader, headers);
+}
+
+void addW3CHeaderFromSentryTrace(
+    SentryTraceHeader traceHeader, Map<String, dynamic> headers) {
+  headers['traceparent'] = formatAsW3CHeader(traceHeader);
+}
+
+String formatAsW3CHeader(SentryTraceHeader traceHeader) {
+  final sampled = traceHeader.sampled;
+  final traceFlags = sampled != null && sampled ? '01' : '00';
+  return '00-${traceHeader.traceId}-${traceHeader.spanId}-$traceFlags';
+}
+
 void addBaggageHeaderFromSpan(
   ISentrySpan span,
   Map<String, dynamic> headers, {

dart/test/utils/tracing_utils_test.dart

@@ -112,6 +112,41 @@ void main() {
       expect(headers[baggage.name], newValue);
     });
 
+    group('$addW3CHeaderFromSentryTrace', () {
+      final fixture = Fixture();
+      final headerName = 'traceparent';
+      final headerValue =
+          '00-${fixture._context.traceId}-${fixture._context.spanId}-01';
+
+      test('formats SentryTraceHeader as W3C header', () {
+        final sut = fixture.getSut();
+        final sentryHeader = sut.toSentryTrace();
+
+        final w3cHeader = formatAsW3CHeader(sentryHeader);
+
+        expect(w3cHeader, headerValue);
+      });
+
+      test('adds W3C traceparent from span', () {
+        final headers = <String, String>{};
+        final sut = fixture.getSut();
+
+        addW3CHeaderFromSpan(sut, headers);
+
+        expect(headers[headerName], headerValue);
+      });
+
+      test('adds W3C traceparent header', () {
+        final headers = <String, String>{};
+        final sut = fixture.getSut();
+        final sentryHeader = sut.toSentryTrace();
+
+        addW3CHeaderFromSentryTrace(sentryHeader, headers);
+
+        expect(headers[headerName], headerValue);
+      });
+    });
+
     test('overwrites duplicate key values', () {
       final headers = <String, String>{};
       final oldValue =

dio/lib/src/tracing_client_adapter.dart

@@ -58,6 +58,7 @@ class TracingClientAdapter implements HttpClientAdapter {
       )) {
         if (span != null) {
           addSentryTraceHeaderFromSpan(span, options.headers);
+          addW3CHeaderFromSpan(span, request.headers);
           addBaggageHeaderFromSpan(
             span,
             options.headers,
@@ -72,6 +73,7 @@ class TracingClientAdapter implements HttpClientAdapter {
 
           final traceHeader = propagationContext.toSentryTrace();
           addSentryTraceHeader(traceHeader, options.headers);
+          addW3CHeaderFromSentryTrace(traceHeader, options.headers);
 
           final baggage = propagationContext.baggage;
           if (baggage != null) {