GH-522 - Support for package info types.

Introduce @PackageInfo annotation to allow marking a types as alternative to Java's native package-info.java so that annotation lookups on a JavaPackage will also find annotations placed on that type. Useful to declare package scoped metadata like @ApplicationModule and @NamedInterface for languages that do not support packages well enough (read: Kotlin).

spring-modulith-core/src/test/java/example/ni/ontype/Exposed.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2024 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.ni.ontype;
+
+/**
+ * @author Oliver Drotbohm
+ */
+public class Exposed {}

spring-modulith-core/src/test/java/example/ni/ontype/Marker.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2024 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.ni.ontype;
+
+import org.springframework.modulith.NamedInterface;
+import org.springframework.modulith.PackageInfo;
+
+/**
+ * @author Oliver Drotbohm
+ */
+@PackageInfo
+@NamedInterface
+class Marker {
+
+}

spring-modulith-core/src/test/java/org/springframework/modulith/core/NamedInterfacesUnitTests.java

@@ -23,6 +23,7 @@ import example.ni.api.ApiType;
 import example.ni.internal.AdditionalSpiType;
 import example.ni.internal.DefaultedNamedInterfaceType;
 import example.ni.internal.Internal;
+import example.ni.ontype.Exposed;
 import example.ni.spi.SpiType;
 import example.ninvalid.InvalidDefaultNamedInterface;
 
@@ -46,13 +47,14 @@ class NamedInterfacesUnitTests {
 		var interfaces = NamedInterfaces.discoverNamedInterfaces(javaPackage);
 
 		assertThat(interfaces).map(NamedInterface::getName)
-				.containsExactlyInAnyOrder(NamedInterface.UNNAMED_NAME, "api", "spi", "kpi", "internal");
+				.containsExactlyInAnyOrder(NamedInterface.UNNAMED_NAME, "api", "spi", "kpi", "internal", "ontype");
 
 		assertInterfaceContains(interfaces, NamedInterface.UNNAMED_NAME, RootType.class);
 		assertInterfaceContains(interfaces, "api", ApiType.class, AnnotatedNamedInterfaceType.class);
 		assertInterfaceContains(interfaces, "spi", SpiType.class, AdditionalSpiType.class);
 		assertInterfaceContains(interfaces, "kpi", AdditionalSpiType.class);
 		assertInterfaceContains(interfaces, "internal", DefaultedNamedInterfaceType.class);
+		assertInterfaceContains(interfaces, "ontype", Exposed.class);
 	}
 
 	@Test // GH-183
@@ -72,7 +74,7 @@ class NamedInterfacesUnitTests {
 		var interfaces = NamedInterfaces.forOpen(javaPackage);
 
 		assertThat(interfaces).map(NamedInterface::getName)
-				.containsExactlyInAnyOrder(NamedInterface.UNNAMED_NAME, "api", "spi", "kpi", "internal");
+				.containsExactlyInAnyOrder(NamedInterface.UNNAMED_NAME, "api", "spi", "kpi", "internal", "ontype");
 
 		assertInterfaceContains(interfaces, NamedInterface.UNNAMED_NAME, RootType.class, Internal.class);
 	}