Merge pull request #1555 from Ant00000ny

* pr/1555:
  Polish "Escape keywords in kotlin package declarations"
  Escape keywords in kotlin package declarations

Closes gh-1555

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/code/kotlin/KotlinProjectGenerationConfiguration.java

@@ -71,17 +71,17 @@ public MainSourceCodeProjectContributor<KotlinTypeDeclaration, KotlinCompilation
 			ObjectProvider<MainCompilationUnitCustomizer<?, ?>> mainCompilationUnitCustomizers,
 			ObjectProvider<MainSourceCodeCustomizer<?, ?, ?>> mainSourceCodeCustomizers) {
 		return new MainSourceCodeProjectContributor<>(this.description, KotlinSourceCode::new,
-				new KotlinSourceCodeWriter(this.indentingWriterFactory), mainApplicationTypeCustomizers,
-				mainCompilationUnitCustomizers, mainSourceCodeCustomizers);
+				new KotlinSourceCodeWriter(this.description.getLanguage(), this.indentingWriterFactory),
+				mainApplicationTypeCustomizers, mainCompilationUnitCustomizers, mainSourceCodeCustomizers);
 	}
 
 	@Bean
 	public TestSourceCodeProjectContributor<KotlinTypeDeclaration, KotlinCompilationUnit, KotlinSourceCode> testKotlinSourceCodeProjectContributor(
 			ObjectProvider<TestApplicationTypeCustomizer<?>> testApplicationTypeCustomizers,
 			ObjectProvider<TestSourceCodeCustomizer<?, ?, ?>> testSourceCodeCustomizers) {
 		return new TestSourceCodeProjectContributor<>(this.description, KotlinSourceCode::new,
-				new KotlinSourceCodeWriter(this.indentingWriterFactory), testApplicationTypeCustomizers,
-				testSourceCodeCustomizers);
+				new KotlinSourceCodeWriter(this.description.getLanguage(), this.indentingWriterFactory),
+				testApplicationTypeCustomizers, testSourceCodeCustomizers);
 	}
 
 	@Bean

initializr-generator/src/main/java/io/spring/initializr/generator/language/Language.java

@@ -24,6 +24,7 @@
  * A language in which a generated project can be written.
  *
  * @author Andy Wilkinson
+ * @author Moritz Halbritter
  */
 public interface Language {
 
@@ -50,6 +51,19 @@ public interface Language {
 	 */
 	String sourceFileExtension();
 
+	/**
+	 * Whether the language supports escaping keywords in package declarations.
+	 * @return whether the language supports escaping keywords in package declarations.
+	 */
+	boolean supportsEscapingKeywordsInPackage();
+
+	/**
+	 * Whether the given {@code input} is a keyword.
+	 * @param input the input
+	 * @return whether the input is a keyword
+	 */
+	boolean isKeyword(String input);
+
 	static Language forId(String id, String jvmVersion) {
 		return SpringFactoriesLoader.loadFactories(LanguageFactory.class, LanguageFactory.class.getClassLoader())
 			.stream()

initializr-generator/src/main/java/io/spring/initializr/generator/language/groovy/GroovyLanguage.java

@@ -16,16 +16,26 @@
 
 package io.spring.initializr.generator.language.groovy;
 
+import java.util.Set;
+
 import io.spring.initializr.generator.language.AbstractLanguage;
 import io.spring.initializr.generator.language.Language;
 
 /**
  * Groovy {@link Language}.
  *
  * @author Stephane Nicoll
+ * @author Moritz Halbritter
  */
 public final class GroovyLanguage extends AbstractLanguage {
 
+	// See https://docs.groovy-lang.org/latest/html/documentation/#_keywords
+	private static final Set<String> KEYWORDS = Set.of("abstract", "assert", "break", "case", "catch", "class", "const",
+			"continue", "def", "default", "do", "else", "enum", "extends", "final", "finally", "for", "goto", "if",
+			"implements", "import", "instanceof", "interface", "native", "new", "null", "non-sealed", "package",
+			"public", "protected", "private", "return", "static", "strictfp", "super", "switch", "synchronized", "this",
+			"threadsafe", "throw", "throws", "transient", "try", "while");
+
 	/**
 	 * Groovy {@link Language} identifier.
 	 */
@@ -39,4 +49,14 @@ public GroovyLanguage(String jvmVersion) {
 		super(ID, jvmVersion, "groovy");
 	}
 
+	@Override
+	public boolean supportsEscapingKeywordsInPackage() {
+		return false;
+	}
+
+	@Override
+	public boolean isKeyword(String input) {
+		return KEYWORDS.contains(input);
+	}
+
 }

initializr-generator/src/main/java/io/spring/initializr/generator/language/java/JavaLanguage.java

@@ -16,6 +16,8 @@
 
 package io.spring.initializr.generator.language.java;
 
+import javax.lang.model.SourceVersion;
+
 import io.spring.initializr.generator.language.AbstractLanguage;
 import io.spring.initializr.generator.language.Language;
 
@@ -40,4 +42,14 @@ public JavaLanguage(String jvmVersion) {
 		super(ID, jvmVersion, "java");
 	}
 
+	@Override
+	public boolean supportsEscapingKeywordsInPackage() {
+		return false;
+	}
+
+	@Override
+	public boolean isKeyword(String input) {
+		return SourceVersion.isKeyword(input);
+	}
+
 }

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

@@ -16,16 +16,26 @@
 
 package io.spring.initializr.generator.language.kotlin;
 
+import java.util.Set;
+
 import io.spring.initializr.generator.language.AbstractLanguage;
 import io.spring.initializr.generator.language.Language;
 
 /**
  * Kotlin {@link Language}.
  *
  * @author Stephane Nicoll
+ * @author Moritz Halbritter
  */
 public final class KotlinLanguage extends AbstractLanguage {
 
+	// 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> 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");
+
 	/**
 	 * Kotlin {@link Language} identifier.
 	 */
@@ -39,4 +49,14 @@ public KotlinLanguage(String jvmVersion) {
 		super(ID, jvmVersion, "kt");
 	}
 
+	@Override
+	public boolean supportsEscapingKeywordsInPackage() {
+		return true;
+	}
+
+	@Override
+	public boolean isKeyword(String input) {
+		return KEYWORDS.contains(input);
+	}
+
 }

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

@@ -40,6 +40,7 @@
 import io.spring.initializr.generator.language.CodeBlock;
 import io.spring.initializr.generator.language.CodeBlock.FormattingOptions;
 import io.spring.initializr.generator.language.CompilationUnit;
+import io.spring.initializr.generator.language.Language;
 import io.spring.initializr.generator.language.Parameter;
 import io.spring.initializr.generator.language.SourceCode;
 import io.spring.initializr.generator.language.SourceCodeWriter;
@@ -55,9 +56,12 @@ public class KotlinSourceCodeWriter implements SourceCodeWriter<KotlinSourceCode
 
 	private static final FormattingOptions FORMATTING_OPTIONS = new KotlinFormattingOptions();
 
+	private final Language language;
+
 	private final IndentingWriterFactory indentingWriterFactory;
 
-	public KotlinSourceCodeWriter(IndentingWriterFactory indentingWriterFactory) {
+	public KotlinSourceCodeWriter(Language language, IndentingWriterFactory indentingWriterFactory) {
+		this.language = language;
 		this.indentingWriterFactory = indentingWriterFactory;
 	}
 
@@ -73,7 +77,7 @@ private void writeTo(SourceStructure structure, KotlinCompilationUnit compilatio
 		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()) {
@@ -127,6 +131,12 @@ private void writeTo(SourceStructure structure, KotlinCompilationUnit compilatio
 		}
 	}
 
+	private String escapeKotlinKeywords(String packageName) {
+		return Arrays.stream(packageName.split("\\."))
+			.map((segment) -> this.language.isKeyword(segment) ? "`" + segment + "`" : segment)
+			.collect(Collectors.joining("."));
+	}
+
 	private void writeProperty(IndentingWriter writer, KotlinPropertyDeclaration propertyDeclaration) {
 		writer.println();
 		writeModifiers(writer, propertyDeclaration.getModifiers());

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

@@ -55,7 +55,7 @@ class KotlinSourceCodeWriterTests {
 	@TempDir
 	Path directory;
 
-	private final KotlinSourceCodeWriter writer = new KotlinSourceCodeWriter(
+	private final KotlinSourceCodeWriter writer = new KotlinSourceCodeWriter(new KotlinLanguage(),
 			IndentingWriterFactory.withDefaultSettings());
 
 	@Test
@@ -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

@@ -25,9 +25,8 @@
 import java.util.List;
 import java.util.Map;
 
-import javax.lang.model.SourceVersion;
-
 import com.fasterxml.jackson.annotation.JsonIgnore;
+import io.spring.initializr.generator.language.Language;
 import io.spring.initializr.generator.version.InvalidVersionException;
 import io.spring.initializr.generator.version.Version;
 import io.spring.initializr.generator.version.Version.Format;
@@ -103,11 +102,12 @@ 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 language the project language
 	 * @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, Language language, String defaultPackageName) {
 		if (!StringUtils.hasText(packageName)) {
 			return defaultPackageName;
 		}
@@ -118,12 +118,16 @@ public String cleanPackageName(String packageName, String defaultPackageName) {
 		if (hasInvalidChar(candidate.replace(".", "")) || this.env.invalidPackageNames.contains(candidate)) {
 			return defaultPackageName;
 		}
-		if (hasReservedKeyword(candidate)) {
-			return defaultPackageName;
-		}
-		else {
-			return candidate;
+		if (!supportsEscapingKeywordsInPackage(language)) {
+			if (hasReservedKeyword(language, candidate)) {
+				return defaultPackageName;
+			}
 		}
+		return candidate;
+	}
+
+	private boolean supportsEscapingKeywordsInPackage(Language language) {
+		return (language != null) ? language.supportsEscapingKeywordsInPackage() : false;
 	}
 
 	static String cleanPackageName(String packageName) {
@@ -165,8 +169,11 @@ private static boolean hasInvalidChar(String text) {
 		return false;
 	}
 
-	private static boolean hasReservedKeyword(final String packageName) {
-		return Arrays.stream(packageName.split("\\.")).anyMatch(SourceVersion::isKeyword);
+	private static boolean hasReservedKeyword(Language language, String packageName) {
+		if (language == null) {
+			return false;
+		}
+		return Arrays.stream(packageName.split("\\.")).anyMatch(language::isKeyword);
 	}
 
 	/**