* Simplify functionalTracingEnabled variable logic

* Add `BeanFactoryAwareFunctionRegistryTests.testWrappedWithAroundAdviseNotMessageReturnConfiguration()`
to verify that non-Message return from the target function is wrapped to the `Message` before return
to the `FunctionAroundWrapper`

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/FunctionAroundWrapper.java

@@ -38,9 +38,8 @@ public abstract class FunctionAroundWrapper implements BiFunction<Object, Functi
 
 	@Override
 	public final Object apply(Object input, FunctionInvocationWrapper targetFunction) {
-		String functionalTracingEnabledStr = System.getProperty("spring.sleuth.function.enabled");
-		boolean functionalTracingEnabled =
-			!StringUtils.hasText(functionalTracingEnabledStr) || Boolean.parseBoolean(functionalTracingEnabledStr);
+		String functionalTracingEnabledStr = System.getProperty("spring.sleuth.function.enabled", "true");
+		boolean functionalTracingEnabled = Boolean.parseBoolean(functionalTracingEnabledStr);
 		if (functionalTracingEnabled) {
 			return this.doApply(input, targetFunction);
 		}

spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistryTests.java

@@ -566,6 +566,16 @@ public class BeanFactoryAwareFunctionRegistryTests {
 		assertThat(result.getHeaders().get("after")).isEqualTo("bar");
 	}
 
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	@Test
+	public void testWrappedWithAroundAdviseNotMessageReturnConfiguration() {
+		FunctionCatalog catalog = this.configureCatalog(WrappedWithAroundAdviseNotMessageReturnConfiguration.class);
+		Function f = catalog.lookup("uppercase");
+		Message result = (Message) f.apply(MessageBuilder.withPayload("hello").setHeader("myHeader", "myValue").build());
+		assertThat(result.getHeaders()).containsEntry("myHeader", "myValue").containsEntry("advised", "true");
+		assertThat(result.getPayload()).isEqualTo("HELLO");
+	}
+
 	@SuppressWarnings({ "rawtypes", "unchecked" })
 	@Test
 	public void testEachElementInFluxIsProcessed() {
@@ -917,6 +927,32 @@ public class BeanFactoryAwareFunctionRegistryTests {
 		}
 	}
 
+	@EnableAutoConfiguration
+	@Configuration
+	protected static class WrappedWithAroundAdviseNotMessageReturnConfiguration {
+
+		@Bean
+		public Function<Message<String>, String> uppercase() {
+			return v -> v.getPayload().toUpperCase();
+		}
+
+		@Bean
+		public FunctionAroundWrapper wrapper() {
+			return new FunctionAroundWrapper() {
+
+				@Override
+				protected Object doApply(Object input, FunctionInvocationWrapper targetFunction) {
+					// in this test we know input is a Message
+					Message<?> mInput = (Message<?>) input;
+					Message<?> advisedMessage = MessageBuilder.fromMessage(mInput).setHeader("advised", "true").build();
+					Object result = targetFunction.apply(advisedMessage);
+					assertThat(result).isInstanceOf(Message.class);
+					return result;
+				}
+			};
+		}
+	}
+
 	@EnableAutoConfiguration
 	@Configuration
 	protected static class SampleFunctionConfiguration {