Generating a Kotlin project with a package name containing keywords will result in an unusable project

initializr-generator/src/main/java/io/spring/initializr/generator/language/kotlin/KotlinSourceCodeWriter.java

@@ -55,6 +55,13 @@ public class KotlinSourceCodeWriter implements SourceCodeWriter<KotlinSourceCode
 
 	private static final FormattingOptions FORMATTING_OPTIONS = new KotlinFormattingOptions();
 
+	// Taken from https://kotlinlang.org/docs/keyword-reference.html#hard-keywords
+	// except keywords contains `!` or `?` because they should be handled as invalid
+	// package names already
+	private static final Set<String> KOTLIN_HARD_KEYWORDS = Set.of("package", "as", "typealias", "class", "this",
+			"super", "val", "var", "fun", "for", "null", "true", "false", "is", "in", "throw", "return", "break",
+			"continue", "object", "if", "try", "else", "while", "do", "when", "interface", "typeof");
+
 	private final IndentingWriterFactory indentingWriterFactory;
 
 	public KotlinSourceCodeWriter(IndentingWriterFactory indentingWriterFactory) {
@@ -68,12 +75,18 @@ public void writeTo(SourceStructure structure, KotlinSourceCode sourceCode) thro
 		}
 	}
 
+	private static String escapeKotlinKeywords(String packageName) {
+		return Arrays.stream(packageName.split("\\."))
+			.map((segment) -> KOTLIN_HARD_KEYWORDS.contains(segment) ? "`" + segment + "`" : segment)
+			.collect(Collectors.joining("."));
+	}
+
 	private void writeTo(SourceStructure structure, KotlinCompilationUnit compilationUnit) throws IOException {
 		Path output = structure.createSourceFile(compilationUnit.getPackageName(), compilationUnit.getName());
 		Files.createDirectories(output.getParent());
 		try (IndentingWriter writer = this.indentingWriterFactory.createIndentingWriter("kotlin",
 				Files.newBufferedWriter(output))) {
-			writer.println("package " + compilationUnit.getPackageName());
+			writer.println("package " + escapeKotlinKeywords(compilationUnit.getPackageName()));
 			writer.println();
 			Set<String> imports = determineImports(compilationUnit);
 			if (!imports.isEmpty()) {

initializr-generator/src/test/java/io/spring/initializr/generator/language/kotlin/KotlinSourceCodeWriterTests.java

@@ -361,6 +361,54 @@ void functionWithParameterAnnotation() throws IOException {
 				"    fun something(@Service service: MyService) {", "    }", "", "}");
 	}
 
+	@Test
+	void reservedKeywordsStartPackageName() throws IOException {
+		KotlinSourceCode sourceCode = new KotlinSourceCode();
+		sourceCode.createCompilationUnit("fun.example.demo", "Test");
+		List<String> lines = writeSingleType(sourceCode, "fun/example/demo/Test.kt");
+		assertThat(lines).containsExactly("package `fun`.example.demo");
+	}
+
+	@Test
+	void reservedKeywordsMiddlePackageName() throws IOException {
+		KotlinSourceCode sourceCode = new KotlinSourceCode();
+		sourceCode.createCompilationUnit("com.false.demo", "Test");
+		List<String> lines = writeSingleType(sourceCode, "com/false/demo/Test.kt");
+		assertThat(lines).containsExactly("package com.`false`.demo");
+	}
+
+	@Test
+	void reservedKeywordsEndPackageName() throws IOException {
+		KotlinSourceCode sourceCode = new KotlinSourceCode();
+		sourceCode.createCompilationUnit("com.example.in", "Test");
+		List<String> lines = writeSingleType(sourceCode, "com/example/in/Test.kt");
+		assertThat(lines).containsExactly("package com.example.`in`");
+	}
+
+	@Test
+	void reservedJavaKeywordsStartPackageName() throws IOException {
+		KotlinSourceCode sourceCode = new KotlinSourceCode();
+		sourceCode.createCompilationUnit("package.fun.example.demo", "Test");
+		List<String> lines = writeSingleType(sourceCode, "package/fun/example/demo/Test.kt");
+		assertThat(lines).containsExactly("package `package`.`fun`.example.demo");
+	}
+
+	@Test
+	void reservedJavaKeywordsMiddlePackageName() throws IOException {
+		KotlinSourceCode sourceCode = new KotlinSourceCode();
+		sourceCode.createCompilationUnit("com.package.demo", "Test");
+		List<String> lines = writeSingleType(sourceCode, "com/package/demo/Test.kt");
+		assertThat(lines).containsExactly("package com.`package`.demo");
+	}
+
+	@Test
+	void reservedJavaKeywordsEndPackageName() throws IOException {
+		KotlinSourceCode sourceCode = new KotlinSourceCode();
+		sourceCode.createCompilationUnit("com.example.package", "Test");
+		List<String> lines = writeSingleType(sourceCode, "com/example/package/Test.kt");
+		assertThat(lines).containsExactly("package com.example.`package`");
+	}
+
 	private List<String> writeSingleType(KotlinSourceCode sourceCode, String location) throws IOException {
 		Path source = writeSourceCode(sourceCode).resolve(location);
 		try (InputStream stream = Files.newInputStream(source)) {

initializr-metadata/src/main/java/io/spring/initializr/metadata/InitializrConfiguration.java

@@ -103,11 +103,12 @@ public String generateApplicationName(String name) {
 	 * The package name cannot be cleaned if the specified {@code packageName} is
 	 * {@code null} or if it contains an invalid character for a class identifier.
 	 * @param packageName the package name
+	 * @param isKotlin if the package name clean is for kotlin project
 	 * @param defaultPackageName the default package name
 	 * @return the cleaned package name
 	 * @see Env#getInvalidPackageNames()
 	 */
-	public String cleanPackageName(String packageName, String defaultPackageName) {
+	public String cleanPackageName(String packageName, boolean isKotlin, String defaultPackageName) {
 		if (!StringUtils.hasText(packageName)) {
 			return defaultPackageName;
 		}
@@ -118,7 +119,9 @@ public String cleanPackageName(String packageName, String defaultPackageName) {
 		if (hasInvalidChar(candidate.replace(".", "")) || this.env.invalidPackageNames.contains(candidate)) {
 			return defaultPackageName;
 		}
-		if (hasReservedKeyword(candidate)) {
+
+		// No check for Kotlin as its reserved keywords will be escaped later
+		if (!isKotlin && hasReservedKeyword(candidate)) {
 			return defaultPackageName;
 		}
 		else {

initializr-metadata/src/test/java/io/spring/initializr/metadata/InitializrConfigurationTests.java

@@ -119,77 +119,166 @@ void generateApplicationNameAnotherInvalidApplicationName() {
 
 	@Test
 	void generatePackageNameSimple() {
-		assertThat(this.properties.cleanPackageName("com.foo", "com.example")).isEqualTo("com.foo");
+		assertThat(this.properties.cleanPackageName("com.foo", false, "com.example")).isEqualTo("com.foo");
 	}
 
 	@Test
 	void generatePackageNameSimpleUnderscore() {
-		assertThat(this.properties.cleanPackageName("com.my_foo", "com.example")).isEqualTo("com.my_foo");
+		assertThat(this.properties.cleanPackageName("com.my_foo", false, "com.example")).isEqualTo("com.my_foo");
 	}
 
 	@Test
 	void generatePackageNameSimpleColon() {
-		assertThat(this.properties.cleanPackageName("com:foo", "com.example")).isEqualTo("com.foo");
+		assertThat(this.properties.cleanPackageName("com:foo", false, "com.example")).isEqualTo("com.foo");
 	}
 
 	@Test
 	void generatePackageNameMultipleDashes() {
-		assertThat(this.properties.cleanPackageName("com.foo--bar", "com.example")).isEqualTo("com.foo__bar");
+		assertThat(this.properties.cleanPackageName("com.foo--bar", false, "com.example")).isEqualTo("com.foo__bar");
 	}
 
 	@Test
 	void generatePackageNameMultipleSpaces() {
-		assertThat(this.properties.cleanPackageName("  com   foo  ", "com.example")).isEqualTo("com.foo");
+		assertThat(this.properties.cleanPackageName("  com   foo  ", false, "com.example")).isEqualTo("com.foo");
 	}
 
 	@Test
 	void generatePackageNameNull() {
-		assertThat(this.properties.cleanPackageName(null, "com.example")).isEqualTo("com.example");
+		assertThat(this.properties.cleanPackageName(null, false, "com.example")).isEqualTo("com.example");
 	}
 
 	@Test
 	void generatePackageNameDot() {
-		assertThat(this.properties.cleanPackageName(".", "com.example")).isEqualTo("com.example");
+		assertThat(this.properties.cleanPackageName(".", false, "com.example")).isEqualTo("com.example");
 	}
 
 	@Test
 	void generatePackageNameWhitespaces() {
-		assertThat(this.properties.cleanPackageName("    ", "com.example")).isEqualTo("com.example");
+		assertThat(this.properties.cleanPackageName("    ", false, "com.example")).isEqualTo("com.example");
 	}
 
 	@Test
 	void generatePackageNameInvalidStartCharacter() {
-		assertThat(this.properties.cleanPackageName("0com.foo", "com.example")).isEqualTo("_com.foo");
+		assertThat(this.properties.cleanPackageName("0com.foo", false, "com.example")).isEqualTo("_com.foo");
 	}
 
 	@Test
 	void generatePackageNameVersion() {
-		assertThat(this.properties.cleanPackageName("com.foo.test-1.4.5", "com.example")).isEqualTo("com.foo.test_145");
+		assertThat(this.properties.cleanPackageName("com.foo.test-1.4.5", false, "com.example"))
+			.isEqualTo("com.foo.test_145");
 	}
 
 	@Test
 	void generatePackageNameInvalidPackageName() {
-		assertThat(this.properties.cleanPackageName("org.springframework", "com.example")).isEqualTo("com.example");
+		assertThat(this.properties.cleanPackageName("org.springframework", false, "com.example"))
+			.isEqualTo("com.example");
 	}
 
 	@Test
 	void generatePackageNameReservedKeywordsMiddleOfPackageName() {
-		assertThat(this.properties.cleanPackageName("com.return.foo", "com.example")).isEqualTo("com.example");
+		assertThat(this.properties.cleanPackageName("com.return.foo", false, "com.example")).isEqualTo("com.example");
 	}
 
 	@Test
 	void generatePackageNameReservedKeywordsStartOfPackageName() {
-		assertThat(this.properties.cleanPackageName("false.com.foo", "com.example")).isEqualTo("com.example");
+		assertThat(this.properties.cleanPackageName("false.com.foo", false, "com.example")).isEqualTo("com.example");
 	}
 
 	@Test
 	void generatePackageNameReservedKeywordsEndOfPackageName() {
-		assertThat(this.properties.cleanPackageName("com.foo.null", "com.example")).isEqualTo("com.example");
+		assertThat(this.properties.cleanPackageName("com.foo.null", false, "com.example")).isEqualTo("com.example");
 	}
 
 	@Test
 	void generatePackageNameReservedKeywordsEntirePackageName() {
-		assertThat(this.properties.cleanPackageName("public", "com.example")).isEqualTo("com.example");
+		assertThat(this.properties.cleanPackageName("public", false, "com.example")).isEqualTo("com.example");
+	}
+
+	@Test
+	void generateKotlinPackageNameSimple() {
+		assertThat(this.properties.cleanPackageName("com.foo", true, "com.example")).isEqualTo("com.foo");
+	}
+
+	@Test
+	void generateKotlinPackageNameSimpleUnderscore() {
+		assertThat(this.properties.cleanPackageName("com.my_foo", true, "com.example")).isEqualTo("com.my_foo");
+	}
+
+	@Test
+	void generateKotlinPackageNameSimpleColon() {
+		assertThat(this.properties.cleanPackageName("com:foo", true, "com.example")).isEqualTo("com.foo");
+	}
+
+	@Test
+	void generateKotlinPackageNameMultipleDashes() {
+		assertThat(this.properties.cleanPackageName("com.foo--bar", true, "com.example")).isEqualTo("com.foo__bar");
+	}
+
+	@Test
+	void generateKotlinPackageNameMultipleSpaces() {
+		assertThat(this.properties.cleanPackageName("  com   foo  ", true, "com.example")).isEqualTo("com.foo");
+	}
+
+	@Test
+	void generateKotlinPackageNameNull() {
+		assertThat(this.properties.cleanPackageName(null, true, "com.example")).isEqualTo("com.example");
+	}
+
+	@Test
+	void generateKotlinPackageNameDot() {
+		assertThat(this.properties.cleanPackageName(".", true, "com.example")).isEqualTo("com.example");
+	}
+
+	@Test
+	void generateKotlinPackageNameWhitespaces() {
+		assertThat(this.properties.cleanPackageName("    ", true, "com.example")).isEqualTo("com.example");
+	}
+
+	@Test
+	void generateKotlinPackageNameInvalidStartCharacter() {
+		assertThat(this.properties.cleanPackageName("0com.foo", true, "com.example")).isEqualTo("_com.foo");
+	}
+
+	@Test
+	void generateKotlinPackageNameVersion() {
+		assertThat(this.properties.cleanPackageName("com.foo.test-1.4.5", true, "com.example"))
+			.isEqualTo("com.foo.test_145");
+	}
+
+	@Test
+	void generateKotlinPackageNameInvalidPackageName() {
+		assertThat(this.properties.cleanPackageName("org.springframework", true, "com.example"))
+			.isEqualTo("com.example");
+	}
+
+	@Test
+	void generateKotlinPackageNameReservedKeywordsMiddleOfPackageName() {
+		assertThat(this.properties.cleanPackageName("com.return.foo", true, "com.example")).isEqualTo("com.return.foo");
+	}
+
+	@Test
+	void generateKotlinPackageNameReservedKeywordsStartOfPackageName() {
+		assertThat(this.properties.cleanPackageName("false.com.foo", true, "com.example")).isEqualTo("false.com.foo");
+	}
+
+	@Test
+	void generateKotlinPackageNameReservedKeywordsEndOfPackageName() {
+		assertThat(this.properties.cleanPackageName("com.foo.null", true, "com.example")).isEqualTo("com.foo.null");
+	}
+
+	@Test
+	void generateKotlinPackageNameReservedChar() {
+		assertThat(this.properties.cleanPackageName("com._foo.null", true, "com.example")).isEqualTo("com._foo.null");
+	}
+
+	@Test
+	void generateKotlinPackageNameJavaReservedKeywords() {
+		assertThat(this.properties.cleanPackageName("public", true, "com.example")).isEqualTo("public");
+	}
+
+	@Test
+	void generateKotlinPackageNameJavaReservedKeywordsEntirePackageName() {
+		assertThat(this.properties.cleanPackageName("public.package", true, "com.example")).isEqualTo("public.package");
 	}
 
 	@Test

initializr-web/src/main/java/io/spring/initializr/web/project/MetadataProjectDescriptionCustomizer.java

@@ -16,8 +16,11 @@
 
 package io.spring.initializr.web.project;
 
+import java.util.Optional;
 import java.util.function.Supplier;
 
+import io.spring.initializr.generator.language.Language;
+import io.spring.initializr.generator.language.kotlin.KotlinLanguage;
 import io.spring.initializr.generator.project.MutableProjectDescription;
 import io.spring.initializr.generator.project.ProjectDescriptionCustomizer;
 import io.spring.initializr.generator.version.Version;
@@ -64,8 +67,14 @@ public void customize(MutableProjectDescription description) {
 		else if (targetArtifactId.equals(description.getName())) {
 			description.setName(cleanMavenCoordinate(targetArtifactId, "-"));
 		}
+
+		boolean isKotlin = Optional.ofNullable(description.getLanguage())
+			.map(Language::id)
+			.filter((id) -> id.equals(KotlinLanguage.ID))
+			.isPresent();
+
 		description.setPackageName(this.metadata.getConfiguration()
-			.cleanPackageName(description.getPackageName(), this.metadata.getPackageName().getContent()));
+			.cleanPackageName(description.getPackageName(), isKotlin, this.metadata.getPackageName().getContent()));
 		if (description.getPlatformVersion() == null) {
 			description.setPlatformVersion(Version.parse(this.metadata.getBootVersions().getDefault().getId()));
 		}