handle the potential of setting baggage before active trace

Author: ZStriker19

lib/datadog/tracing.rb

@@ -130,7 +130,7 @@ def log_correlation
       def baggage
         # Baggage should not be dependent on there being an active trace.
         # So we create a new TraceOperation if there isn't one.
-        active_trace ||= TraceOperation.new
+        active_trace = self.active_trace || tracer.continue_trace!(nil)
         active_trace.baggage
       end
 

lib/datadog/tracing/tracer.rb

@@ -342,7 +342,8 @@ def build_trace(digest = nil)
             trace_state: digest.trace_state,
             trace_state_unknown_fields: digest.trace_state_unknown_fields,
             remote_parent: digest.span_remote,
-            tracer: self
+            tracer: self,
+            baggage: digest.baggage
           )
         else
           TraceOperation.new(

spec/datadog/tracing/tracer_spec.rb

@@ -1059,6 +1059,36 @@
       end
     end
   end
+
+  describe '#baggage_tracing_interactions' do
+    it 'baggage set before active trace creates active trace' do
+      Datadog::Tracing.baggage['key'] = 'value'
+      Datadog::Tracing.trace('operation') do |_span, trace|
+        expect(trace.to_digest.baggage).to eq('key' => 'value')
+      end
+    end
+
+    it 'baggage set after trace finish creates new traceoperation with baggage value' do
+      Datadog::Tracing.trace('operation') do |_span, _trace|
+        expect(Datadog::Tracing.baggage).to be_empty
+      end
+      Datadog::Tracing.baggage['key'] = 'value'
+      expect(Datadog::Tracing.active_trace.to_digest.baggage).to eq('key' => 'value')
+    end
+  end
+
+  it 'baggage value is overridden inside an active trace' do
+    Datadog::Tracing.trace('operation') do |_span, trace|
+      Datadog::Tracing.baggage['key'] = 'value'
+      expect(trace.to_digest.baggage).to eq('key' => 'value')
+    end
+  end
+
+  it 'incoming headers overrides existing baggage' do
+    Datadog::Tracing.baggage['key'] = 'value'
+    Datadog::Tracing.continue_trace!(Datadog::Tracing::TraceDigest.new(baggage: { 'key1' => 'value1' }))
+    expect(Datadog::Tracing.active_trace.to_digest.baggage).to eq('key1' => 'value1')
+  end
 end
 
 RSpec.describe Datadog::Tracing::Tracer::TraceCompleted do