GH-613 - Add SPI to support external ApplicationModuleSource contributions.

We now expose ApplicationModuleSourceFactory as Spring Factories-based SPI interface to further contribute ApplicationModuleSource instances either from a provided root package subject for module detection through a (potentially customized) ApplicationModuleDetectionStrategy or by explicitly listing particular module base packages.

spring-modulith-core/src/test/java/contributed/ApplicationModuleSourceContribution.java

@@ -0,0 +1,56 @@
+/*
+ * 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 contributed;
+
+import java.util.List;
+
+import org.springframework.modulith.core.ApplicationModuleDetectionStrategy;
+import org.springframework.modulith.core.ApplicationModuleSourceFactory;
+
+/**
+ * Example {@link ApplicationModuleSourceFactory}.
+ *
+ * @author Oliver Drotbohm
+ */
+public class ApplicationModuleSourceContribution implements ApplicationModuleSourceFactory {
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.modulith.core.ApplicationModuleSourceFactory#getRootPackages()
+	 */
+	@Override
+	public List<String> getRootPackages() {
+		return List.of("contributed");
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.modulith.core.ApplicationModuleSourceFactory#getApplicationModuleDetectionStrategy()
+	 */
+	@Override
+	public ApplicationModuleDetectionStrategy getApplicationModuleDetectionStrategy() {
+		return ApplicationModuleDetectionStrategy.explicitlyAnnotated();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.modulith.core.ApplicationModuleSourceFactory#getModuleBasePackages()
+	 */
+	@Override
+	public List<String> getModuleBasePackages() {
+		return List.of("contributed.enumerated");
+	}
+}

spring-modulith-core/src/test/java/contributed/detected/package-info.java

@@ -0,0 +1,2 @@
+@org.springframework.modulith.ApplicationModule
+package contributed.detected;

spring-modulith-core/src/test/java/contributed/enumerated/package-info.java

@@ -0,0 +1 @@
+package contributed.enumerated;

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

@@ -0,0 +1,52 @@
+/*
+ * 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 org.springframework.modulith.core;
+
+import static org.assertj.core.api.Assertions.*;
+
+import contributed.ApplicationModuleSourceContribution;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import com.tngtech.archunit.core.importer.ClassFileImporter;
+import com.tngtech.archunit.core.importer.ImportOption;
+
+/**
+ * Unit tests for {@link ApplicationModuleSourceContributions}.
+ *
+ * @author Oliver Drotbohm
+ * @since 1.3
+ */
+class ApplicationModuleSourceContributionsUnitTests {
+
+	@Test // GH-613
+	void detectsContributions() {
+
+		var factories = List.of(new ApplicationModuleSourceContribution());
+		var importer = new ClassFileImporter().withImportOption(new ImportOption.OnlyIncludeTests());
+		var strategy = ApplicationModuleDetectionStrategy.directSubPackage();
+
+		var contributions = new ApplicationModuleSourceContributions(factories, importer::importPackages, strategy, false);
+
+		assertThat(contributions.getRootPackages()).contains("contributed");
+		assertThat(contributions.getSources())
+				.extracting(ApplicationModuleSource::getModuleBasePackage)
+				.extracting(JavaPackage::getName)
+				.containsExactlyInAnyOrder("contributed.detected", "contributed.enumerated");
+	}
+}

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

@@ -110,6 +110,6 @@ public class TestUtils {
 	}
 
 	private static ApplicationModules of(ModulithMetadata metadata, DescribedPredicate<JavaClass> ignores) {
-		return new ApplicationModules(metadata, ignores, false, new ImportOption.OnlyIncludeTests()) {};
+		return new ApplicationModules(metadata, ignores, new ImportOption.OnlyIncludeTests()) {};
 	}
 }