default propagation style is now [Datadog, W3C]

Author: dgoffredo

src/datadog/tracer_config.h

@@ -72,7 +72,8 @@ struct TracerConfig {
   // All styles indicated by `injection_styles` are used for injection.
   // `injection_styles` is overridden by the `DD_TRACE_PROPAGATION_STYLE_INJECT`
   // and `DD_TRACE_PROPAGATION_STYLE` environment variables.
-  std::vector<PropagationStyle> injection_styles = {PropagationStyle::DATADOG};
+  std::vector<PropagationStyle> injection_styles = {PropagationStyle::DATADOG,
+                                                    PropagationStyle::W3C};
 
   // `extraction_styles` indicates with which tracing systems trace propagation
   // will be compatible when extracting (receiving) trace context.
@@ -82,7 +83,8 @@ struct TracerConfig {
   // `extraction_styles` is overridden by the
   // `DD_TRACE_PROPAGATION_STYLE_EXTRACT` and `DD_TRACE_PROPAGATION_STYLE`
   // environment variables.
-  std::vector<PropagationStyle> extraction_styles = {PropagationStyle::DATADOG};
+  std::vector<PropagationStyle> extraction_styles = {PropagationStyle::DATADOG,
+                                                     PropagationStyle::W3C};
 
   // `report_hostname` indicates whether the tracer will include the result of
   // `gethostname` with traces sent to the collector.

test/test_tracer_config.cpp

@@ -1003,12 +1003,12 @@ TEST_CASE("TracerConfig propagation styles") {
   TracerConfig config;
   config.defaults.service = "testsvc";
 
-  SECTION("default style is Datadog") {
+  SECTION("default style is [Datadog, W3C]") {
     auto finalized = finalize_config(config);
     REQUIRE(finalized);
 
     const std::vector<PropagationStyle> expected_styles = {
-        PropagationStyle::DATADOG};
+        PropagationStyle::DATADOG, PropagationStyle::W3C};
 
     REQUIRE(finalized->injection_styles == expected_styles);
     REQUIRE(finalized->extraction_styles == expected_styles);