Ensures that the primitive types are also supported for Stream; fixes gh-2068

spring-cloud-sleuth-instrumentation/src/main/java/org/springframework/cloud/sleuth/instrument/messaging/TraceFunctionAroundWrapper.java

@@ -96,6 +96,14 @@ public class TraceFunctionAroundWrapper extends FunctionAroundWrapper
 		else if (targetFunction.isInputTypePublisher() || targetFunction.isOutputTypePublisher()) {
 			return reactorStream((Publisher) message, targetFunction);
 		}
+		else if (message != null && !(message instanceof Message)) {
+			if (log.isDebugEnabled()) {
+				String messageClass = message.getClass().getName();
+				log.debug("We only support tracing for Message types. You need to wrap your function type ["
+						+ messageClass + "] into [Message<" + messageClass + ">]");
+			}
+			return targetFunction.apply(message); // no instrumentation
+		}
 		return nonReactorStream((Message<byte[]>) message, targetFunction);
 	}
 

spring-cloud-sleuth-instrumentation/src/test/java/org/springframework/cloud/sleuth/instrument/messaging/TraceFunctionAroundWrapperTests.java

@@ -121,6 +121,19 @@ class TraceFunctionAroundWrapperTests {
 		assertThatAllSpansAreStartedAndStopped();
 	}
 
+	@Test
+	void test_tracing_with_function_and_input_as_non_message() {
+		FunctionRegistration<GreeterFunction> registration = new FunctionRegistration<>(new GreeterFunction(),
+				"greeter").type(FunctionType.of(GreeterFunction.class));
+		catalog.register(registration);
+		FunctionInvocationWrapper function = catalog.lookup("greeter");
+
+		String result = (String) wrapper.apply("hello", function);
+
+		assertThat(result).isEqualTo("HELLO");
+		assertThat(tracer.spans).isEmpty();
+	}
+
 	@Test
 	void test_tracing_with_consumer() {
 		GreeterConsumer consumer = new GreeterConsumer();