GH-1043 - Fix module identifier lookup in ApplicationModuleSource.

Before this commit, ApplicationModuleSource inspected all package-info.java contained in given packages, including the sub-packages of those. That caused identifiers explicitly defined in an @ApplicationModule on a package-info.java in nested packages picked up for top-level packages. This is now fixed by only considering the files in the top-level packages.

spring-modulith-core/src/main/java/org/springframework/modulith/core/ApplicationModuleSource.java

@@ -79,7 +79,7 @@ public class ApplicationModuleSource {
 				.flatMap(ANNOTATION_IDENTIFIER_SOURCE::withNestedPackages)
 				.map(it -> {
 
-					var id = ANNOTATION_IDENTIFIER_SOURCE.lookupIdentifier(it)
+					var id = ANNOTATION_IDENTIFIER_SOURCE.lookupIdentifier(it.toSingle())
 							.orElseGet(() -> ApplicationModuleIdentifier.of(
 									fullyQualifiedModuleNames ? it.getName() : rootPackage.getTrailingName(it)));
 

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

@@ -42,4 +42,18 @@ class ApplicationModuleSourceUnitTests {
 				.extracting(ApplicationModuleIdentifier::toString)
 				.contains("ninvalid", "customId", "invalid", "ni", "ni.nested.b.first", "secondCustomized", "ni.nested");
 	}
+
+	@Test // GH-1042
+	void doesNotPickUpIdFromNestedPackages() {
+
+		var pkg = TestUtils.getPackage("reproducers.gh1042");
+
+		var sources = ApplicationModuleSource.from(pkg, ApplicationModuleDetectionStrategy.directSubPackage(), false);
+
+		assertThat(sources)
+				.extracting(ApplicationModuleSource::getIdentifier)
+				.extracting(ApplicationModuleIdentifier::toString)
+				.contains("module", // picked from package name not from annotation in nested package
+						"gh-1042-nested"); // from annotation in nested package
+	}
 }

spring-modulith-core/src/test/java/reproducers/gh1042/module/nested/package-info.java

@@ -0,0 +1,2 @@
+@org.springframework.modulith.ApplicationModule(id = "gh-1042-nested", displayName = "Nested")
+package reproducers.gh1042.module.nested;

spring-modulith-core/src/test/java/reproducers/gh764/nested/package-info.java

@@ -1,2 +0,0 @@
-@org.springframework.modulith.ApplicationModule(displayName = "Nested")
-package reproducers.gh764.nested;