GH-1382 - Add Kotlin support for Change-Aware Test Execution

spring-modulith-junit/src/main/java/org/springframework/modulith/junit/Changes.java

@@ -161,46 +161,60 @@ sealed interface Change permits SourceChange, OtherFileChange {
 		boolean hasOrigin(String nameOrPath);
 
 		/**
-		 * creates a new
-		 *
-		 * @param file
-		 * @return
+		 * Creates a change from a modified file
 		 */
 		static Change of(ModifiedFile file) {
+			boolean isJavaSource = file.isJavaSource();
 
-			if (!file.isJavaSource()) {
+			if (!isJavaSource && !file.isKotlinSource()) {
 				return new OtherFileChange(file.path());
 			}
 
+			var languageConfig = isJavaSource ? LanguageConfig.JAVA : LanguageConfig.KOTLIN;
+			return toSourceChange(file, languageConfig);
+		}
+
+		private static Change toSourceChange(ModifiedFile file, LanguageConfig config) {
 			var withoutExtension = StringUtils.stripFilenameExtension(file.path());
-			var startOfMainDir = withoutExtension.indexOf(JavaSourceChange.STANDARD_SOURCE_DIRECTORY);
-			var startOfTestDir = withoutExtension.indexOf(JavaSourceChange.STANDARD_TEST_SOURCE_DIRECTORY);
+			var startOfMainDir = withoutExtension.indexOf(config.mainDir());
+			var startOfTestDir = withoutExtension.indexOf(config.testDir());
 
 			if (startOfTestDir > -1 && (startOfMainDir < 0 || startOfTestDir < startOfMainDir)) {
 
-				var fullyQualifiedClassName = ClassUtils.convertResourcePathToClassName(
-						withoutExtension.substring(startOfTestDir + JavaSourceChange.STANDARD_TEST_SOURCE_DIRECTORY.length() + 1));
+				var fullyQualifiedClassName = ClassUtils
+						.convertResourcePathToClassName(withoutExtension.substring(startOfTestDir + config.testDir().length() + 1));
 
-				return new JavaTestSourceChange(fullyQualifiedClassName);
+				return config.testFactory().apply(fullyQualifiedClassName);
 			}
 
 			if (startOfMainDir > -1 && (startOfTestDir < 0 || startOfMainDir < startOfTestDir)) {
 
-				var fullyQualifiedClassName = ClassUtils.convertResourcePathToClassName(
-						withoutExtension.substring(startOfMainDir + JavaSourceChange.STANDARD_SOURCE_DIRECTORY.length() + 1));
+				var fullyQualifiedClassName = ClassUtils
+						.convertResourcePathToClassName(withoutExtension.substring(startOfMainDir + config.mainDir().length() + 1));
 
-				return new JavaSourceChange(fullyQualifiedClassName);
+				return config.mainFactory().apply(fullyQualifiedClassName);
 			}
 
-			return new JavaSourceChange(ClassUtils.convertResourcePathToClassName(withoutExtension));
+			return config.mainFactory().apply(ClassUtils.convertResourcePathToClassName(withoutExtension));
+		}
+
+		record LanguageConfig(String mainDir, String testDir, Function<String, ? extends SourceChange> mainFactory,
+				Function<String, ? extends SourceChange> testFactory) {
+
+			static final LanguageConfig JAVA = new LanguageConfig(JavaSourceChange.STANDARD_SOURCE_DIRECTORY,
+					JavaSourceChange.STANDARD_TEST_SOURCE_DIRECTORY, JavaSourceChange::new, JavaTestSourceChange::new);
+
+			static final LanguageConfig KOTLIN = new LanguageConfig(KotlinSourceChange.STANDARD_SOURCE_DIRECTORY,
+					KotlinSourceChange.STANDARD_TEST_SOURCE_DIRECTORY, KotlinSourceChange::new, KotlinTestSourceChange::new);
 		}
 
 		/**
 		 * A change to a source file.
 		 *
 		 * @author Oliver Drotbohm
 		 */
-		sealed interface SourceChange extends Change permits JavaSourceChange, JavaTestSourceChange {
+		sealed interface SourceChange extends Change
+				permits KotlinSourceChange, KotlinTestSourceChange, JavaSourceChange, JavaTestSourceChange {
 
 			String fullyQualifiedClassName();
 
@@ -243,7 +257,22 @@ public final String toString() {
 		 * @author David Bilge
 		 * @author Oliver Drotbohm
 		 */
-		record JavaTestSourceChange(String fullyQualifiedClassName) implements SourceChange {}
+		record JavaTestSourceChange(String fullyQualifiedClassName) implements SourceChange {
+		}
+
+		/**
+		 * A change in a Kotlin source file.
+		 */
+		record KotlinSourceChange(String fullyQualifiedClassName) implements SourceChange {
+			private static final String STANDARD_SOURCE_DIRECTORY = "src/main/kotlin";
+			private static final String STANDARD_TEST_SOURCE_DIRECTORY = "src/test/kotlin";
+		}
+
+		/**
+		 * A change in a Kotlin test source file.
+		 */
+		record KotlinTestSourceChange(String fullyQualifiedClassName) implements SourceChange {
+		}
 
 		/**
 		 * Some arbitrary file change.

spring-modulith-junit/src/main/java/org/springframework/modulith/junit/diff/ModifiedFile.java

@@ -37,6 +37,13 @@ public boolean isJavaSource() {
 		return "java".equalsIgnoreCase(StringUtils.getFilenameExtension(path));
 	}
 
+	/**
+	 * Returns whether the modified file is Kotlin source file.
+	 */
+	public boolean isKotlinSource() {
+		return "kt".equalsIgnoreCase(StringUtils.getFilenameExtension(path));
+	}
+
 	public static Stream<ModifiedFile> of(String... paths) {
 		return Arrays.stream(paths).map(ModifiedFile::new);
 	}

spring-modulith-junit/src/test/java/org/springframework/modulith/junit/ChangesUnitTests.java

@@ -24,6 +24,8 @@
 import org.junit.jupiter.api.TestFactory;
 import org.springframework.modulith.junit.Changes.Change.JavaSourceChange;
 import org.springframework.modulith.junit.Changes.Change.JavaTestSourceChange;
+import org.springframework.modulith.junit.Changes.Change.KotlinSourceChange;
+import org.springframework.modulith.junit.Changes.Change.KotlinTestSourceChange;
 import org.springframework.modulith.junit.Changes.Change.OtherFileChange;
 import org.springframework.modulith.junit.diff.ModifiedFile;
 
@@ -73,6 +75,8 @@ void shouldInterpredModifiedFilePathsCorrectly() {
 		var modifiedFilePaths = Stream.of(
 				"src/main/java/org/springframework/modulith/junit/Changes.java",
 				"src/test/java/org/springframework/modulith/ChangesTest.java",
+				"src/test/kotlin/org/springframework/modulith/KotlinServiceTest.kt",
+				"src/main/kotlin/org/springframework/modulith/KotlinService.kt",
 				"src/main/resources/META-INF/additional-spring-configuration-metadata.json")
 				.map(ModifiedFile::new);
 
@@ -84,6 +88,8 @@ void shouldInterpredModifiedFilePathsCorrectly() {
 		assertThat(result).containsExactlyInAnyOrder(
 				new JavaSourceChange("org.springframework.modulith.junit.Changes"),
 				new JavaTestSourceChange("org.springframework.modulith.ChangesTest"),
+				new KotlinTestSourceChange("org.springframework.modulith.KotlinServiceTest"),
+				new KotlinSourceChange("org.springframework.modulith.KotlinService"),
 				new OtherFileChange("src/main/resources/META-INF/additional-spring-configuration-metadata.json"));
 	}
 }