OTEL: don't return a span if not valid

Author: amarziali

dd-java-agent/agent-otel/otel-shim/src/main/java/datadog/opentelemetry/shim/context/OtelContext.java

@@ -45,7 +45,7 @@ public Scope makeCurrent() {
   public <V> V get(ContextKey<V> key) {
     if (OTEL_CONTEXT_SPAN_KEY.equals(key.toString())) {
       AgentSpan span = AgentSpan.fromContext(delegate);
-      if (span != null) {
+      if (span != null && span.isValid()) {
         return (V) toOtelSpan(span);
       }
       // fall-through and check for non-datadog span data

dd-java-agent/instrumentation/opentelemetry/opentelemetry-1.4/src/test/groovy/opentelemetry14/context/propagation/AbstractPropagatorTest.groovy

@@ -4,6 +4,7 @@ import datadog.trace.agent.test.InstrumentationSpecification
 import datadog.trace.api.DDSpanId
 import datadog.trace.api.DDTraceId
 import io.opentelemetry.api.GlobalOpenTelemetry
+import io.opentelemetry.api.trace.Span
 import io.opentelemetry.context.Context
 import io.opentelemetry.context.ThreadLocalContextStorage
 import io.opentelemetry.context.propagation.TextMapPropagator
@@ -102,6 +103,14 @@ abstract class AbstractPropagatorTest extends InstrumentationSpecification {
     (headers, traceId, spanId, sampling) = values
   }
 
+  def "extraction on missing tracecontext should return an empty context"() {
+    when:
+    def headers = ["User-Agent":"test"]
+    def context = propagator().extract(Context.root(), headers, TextMap.INSTANCE)
+    then:
+    assert Span.fromContextOrNull(context) == null : "Should not have a tracing context"
+  }
+
   def expectedTraceId(String traceId) {
     return DDTraceId.fromHex(traceId)
   }