GH-332 - Avoid proxying configuration classes for observability purposes.

We now skip configuration classes for observability-related proxying as it's hard to detect those during the ProxyFactory setup to configure target class proxying. Also, configuration classes are usually no targets of inter-module communication and thus don't need to be observed at all.

spring-modulith-observability/src/test/java/example/sample/SampleConfiguration.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package example.sample;
+
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * @author Oliver Drotbohm
+ */
+@Configuration
+public class SampleConfiguration {}

spring-modulith-observability/src/test/java/org/springframework/modulith/observability/ObservedModuleTypeUnitTests.java

@@ -18,6 +18,7 @@ package org.springframework.modulith.observability;
 import static org.assertj.core.api.Assertions.*;
 
 import example.sample.SampleComponent;
+import example.sample.SampleConfiguration;
 
 import org.junit.jupiter.api.Test;
 import org.springframework.aop.framework.Advised;
@@ -55,6 +56,15 @@ public class ObservedModuleTypeUnitTests {
 
 	@Test // GH-106
 	void considersExposedTypeAsToBeIntercepted() {
-		assertThat(observedType.shouldBeTraced()).isTrue();
+		assertThat(observedType.shouldBeObserved()).isTrue();
+	}
+
+	@Test // GH-332
+	void doesNotObserveConfigurationClasses() {
+
+		var type = module.getArchitecturallyEvidentType(SampleConfiguration.class);
+		var observedType = new ObservedModuleType(modules, new DefaultObservedModule(module), type);
+
+		assertThat(observedType.shouldBeObserved()).isFalse();
 	}
 }