Guard compilation unit from null attributes

Closes gh-975

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

@@ -20,6 +20,8 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
+import org.springframework.util.Assert;
+
 /**
  * A compilation unit that represents an individual source file.
  *
@@ -34,15 +36,30 @@ public abstract class CompilationUnit<T extends TypeDeclaration> {
 
 	private final List<T> typeDeclarations = new ArrayList<>();
 
+	/**
+	 * Create a new instance with the package to use and the name of the type.
+	 * @param packageName the package in which the source file should be located
+	 * @param name the name of the file
+	 */
 	public CompilationUnit(String packageName, String name) {
+		Assert.hasText(packageName, "'packageName' must not be null");
+		Assert.hasText(name, "'name' must not be null");
 		this.packageName = packageName;
 		this.name = name;
 	}
 
+	/**
+	 * Return the package name in which the file should reside.
+	 * @return the package name
+	 */
 	public String getPackageName() {
 		return this.packageName;
 	}
 
+	/**
+	 * Return the name of the source file.
+	 * @return the name of the source file
+	 */
 	public String getName() {
 		return this.name;
 	}

initializr-generator/src/test/java/io/spring/initializr/generator/language/groovy/GroovySourceCodeWriterTests.java

@@ -31,6 +31,7 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 
 /**
  * Tests for {@link GroovySourceCodeWriter}.
@@ -46,6 +47,18 @@ class GroovySourceCodeWriterTests {
 	private final GroovySourceCodeWriter writer = new GroovySourceCodeWriter(
 			IndentingWriterFactory.withDefaultSettings());
 
+	@Test
+	void nullPackageInvalidCompilationUnit() {
+		GroovySourceCode sourceCode = new GroovySourceCode();
+		assertThatIllegalArgumentException().isThrownBy(() -> sourceCode.createCompilationUnit(null, "Test"));
+	}
+
+	@Test
+	void nullNameInvalidCompilationUnit() {
+		GroovySourceCode sourceCode = new GroovySourceCode();
+		assertThatIllegalArgumentException().isThrownBy(() -> sourceCode.createCompilationUnit("com.example", null));
+	}
+
 	@Test
 	void emptyCompilationUnit() throws IOException {
 		GroovySourceCode sourceCode = new GroovySourceCode();

initializr-generator/src/test/java/io/spring/initializr/generator/language/java/JavaSourceCodeWriterTests.java

@@ -31,6 +31,7 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 
 /**
  * Tests for {@link JavaSourceCodeWriter}.
@@ -45,6 +46,18 @@ class JavaSourceCodeWriterTests {
 
 	private final JavaSourceCodeWriter writer = new JavaSourceCodeWriter(IndentingWriterFactory.withDefaultSettings());
 
+	@Test
+	void nullPackageInvalidCompilationUnit() {
+		JavaSourceCode sourceCode = new JavaSourceCode();
+		assertThatIllegalArgumentException().isThrownBy(() -> sourceCode.createCompilationUnit(null, "Test"));
+	}
+
+	@Test
+	void nullNameInvalidCompilationUnit() {
+		JavaSourceCode sourceCode = new JavaSourceCode();
+		assertThatIllegalArgumentException().isThrownBy(() -> sourceCode.createCompilationUnit("com.example", null));
+	}
+
 	@Test
 	void emptyCompilationUnit() throws IOException {
 		JavaSourceCode sourceCode = new JavaSourceCode();

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

@@ -30,6 +30,7 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 
 /**
  * Tests for {@link KotlinSourceCodeWriter}.
@@ -45,6 +46,18 @@ class KotlinSourceCodeWriterTests {
 	private final KotlinSourceCodeWriter writer = new KotlinSourceCodeWriter(
 			IndentingWriterFactory.withDefaultSettings());
 
+	@Test
+	void nullPackageInvalidCompilationUnit() {
+		KotlinSourceCode sourceCode = new KotlinSourceCode();
+		assertThatIllegalArgumentException().isThrownBy(() -> sourceCode.createCompilationUnit(null, "Test"));
+	}
+
+	@Test
+	void nullNameInvalidCompilationUnit() {
+		KotlinSourceCode sourceCode = new KotlinSourceCode();
+		assertThatIllegalArgumentException().isThrownBy(() -> sourceCode.createCompilationUnit("com.example", null));
+	}
+
 	@Test
 	void emptyCompilationUnit() throws IOException {
 		KotlinSourceCode sourceCode = new KotlinSourceCode();