Fix Span.current() behavior - return Optional.empty() if there is no …

…current span (#8574)

Signed-off-by: Tim Quinn <tim.quinn@oracle.com>

tracing/opentelemetry/src/main/java/io/helidon/tracing/opentelemetry/OpenTelemetryTracerProvider.java

@@ -91,10 +91,17 @@ public static Tracer globalTracer() {
      * @return optional of the current span
      */
     public static Optional<Span> activeSpan() {
-        // OTel returns a no-op span if there is no current one.
-        io.opentelemetry.api.trace.Span otelSpan = io.opentelemetry.api.trace.Span.current();
+        io.opentelemetry.context.Context otelContext = io.opentelemetry.context.Context.current();
 
-        // OTel returns empty baggage if there is no current one.
+        // OTel Span.current() returns a no-op span if there is no current one. Use fromContextOrNull instead to distinguish.
+        io.opentelemetry.api.trace.Span otelSpan =
+                io.opentelemetry.api.trace.Span.fromContextOrNull(otelContext);
+
+        if (otelSpan == null) {
+            return Optional.empty();
+        }
+
+        // OTel Baggage.current() returns empty baggage if there is no current one. That's OK for baggage.
         io.opentelemetry.api.baggage.Baggage otelBaggage = io.opentelemetry.api.baggage.Baggage.current();
 
         // Create the span directly with the retrieved baggage. Ideally, it will be our writable baggage because we had put it

tracing/opentelemetry/src/test/java/io/helidon/tracing/opentelemetry/TestSpanAndBaggage.java

@@ -113,14 +113,11 @@ void testActiveSpanScopeWithBaggage() {
             outerSpan.end(e);
         }
 
-        // There was no active span before outerSpan was activated, so expect the "default" ad-hoc span ID of all zeroes.
+        // There was no active span before outerSpan was activated, so expect an empty current span.
         Optional<Span> currentSpanAfterTryResourcesBlock = Span.current();
         assertThat("Current span just after try-resources block",
                    currentSpanAfterTryResourcesBlock,
-                   OptionalMatcher.optionalPresent());
-        assertThat("Current span just after try-resources block",
-                   currentSpanAfterTryResourcesBlock.get().context().spanId(),
-                   containsString("00000000"));
+                   OptionalMatcher.optionalEmpty());
     }