Add nullability annotations to build-plugin/spring-boot-gradle-plugin

See gh-46587

Author: mhalbritter

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/dsl/SpringBootExtension.java

@@ -28,8 +28,10 @@
 import org.gradle.api.tasks.TaskContainer;
 import org.gradle.api.tasks.TaskProvider;
 import org.gradle.api.tasks.bundling.Jar;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.boot.gradle.tasks.buildinfo.BuildInfo;
+import org.springframework.util.Assert;
 
 /**
  * Entry point to Spring Boot's Gradle DSL.
@@ -85,7 +87,7 @@ public void buildInfo() {
 	 * artifact will be the base name of the {@code bootWar} or {@code bootJar} task.
 	 * @param configurer the task configurer
 	 */
-	public void buildInfo(Action<BuildInfo> configurer) {
+	public void buildInfo(@Nullable Action<BuildInfo> configurer) {
 		TaskContainer tasks = this.project.getTasks();
 		TaskProvider<BuildInfo> bootBuildInfo = tasks.register("bootBuildInfo", BuildInfo.class,
 				this::configureBuildInfoTask);
@@ -109,20 +111,22 @@ private void configureBuildInfoTask(BuildInfo task) {
 	}
 
 	private File determineMainSourceSetResourcesOutputDir() {
-		return this.project.getExtensions()
+		File resourcesDir = this.project.getExtensions()
 			.getByType(JavaPluginExtension.class)
 			.getSourceSets()
 			.getByName(SourceSet.MAIN_SOURCE_SET_NAME)
 			.getOutput()
 			.getResourcesDir();
+		Assert.state(resourcesDir != null, "'resourcesDir' must not be null");
+		return resourcesDir;
 	}
 
-	private String determineArtifactBaseName() {
+	private @Nullable String determineArtifactBaseName() {
 		Jar artifactTask = findArtifactTask();
 		return (artifactTask != null) ? artifactTask.getArchiveBaseName().get() : null;
 	}
 
-	private Jar findArtifactTask() {
+	private @Nullable Jar findArtifactTask() {
 		Jar artifactTask = (Jar) this.project.getTasks().findByName("bootWar");
 		if (artifactTask != null) {
 			return artifactTask;

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/dsl/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Spring Boot Gradle DSL.
  */
+@NullMarked
 package org.springframework.boot.gradle.dsl;
+
+import org.jspecify.annotations.NullMarked;

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/DependencyManagementPluginAction.java

@@ -22,6 +22,8 @@
 import org.gradle.api.Plugin;
 import org.gradle.api.Project;
 
+import org.springframework.util.Assert;
+
 /**
  * {@link Action} that is performed in response to the {@link DependencyManagementPlugin}
  * being applied.
@@ -32,9 +34,10 @@ final class DependencyManagementPluginAction implements PluginApplicationAction
 
 	@Override
 	public void execute(Project project) {
-		project.getExtensions()
-			.findByType(DependencyManagementExtension.class)
-			.imports((importsHandler) -> importsHandler.mavenBom(SpringBootPlugin.BOM_COORDINATES));
+		DependencyManagementExtension extension = project.getExtensions()
+			.findByType(DependencyManagementExtension.class);
+		Assert.state(extension != null, "'extension' must not be null");
+		extension.imports((importsHandler) -> importsHandler.mavenBom(SpringBootPlugin.BOM_COORDINATES));
 	}
 
 	@Override

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/JavaPluginAction.java

@@ -44,11 +44,13 @@
 import org.gradle.api.tasks.compile.JavaCompile;
 import org.gradle.jvm.toolchain.JavaToolchainService;
 import org.gradle.jvm.toolchain.JavaToolchainSpec;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.boot.gradle.dsl.SpringBootExtension;
 import org.springframework.boot.gradle.tasks.bundling.BootBuildImage;
 import org.springframework.boot.gradle.tasks.bundling.BootJar;
 import org.springframework.boot.gradle.tasks.run.BootRun;
+import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
 /**
@@ -123,6 +125,7 @@ private TaskProvider<ResolveMainClassName> configureResolveMainClassNameTask(Pro
 							}
 							SpringBootExtension springBootExtension = project.getExtensions()
 								.findByType(SpringBootExtension.class);
+							Assert.state(springBootExtension != null, "'springBootExtension' must not be null");
 							return springBootExtension.getMainClass().getOrNull();
 						}));
 						resolveMainClassName.getOutputFile()
@@ -147,7 +150,7 @@ private TaskProvider<ResolveMainClassName> configureResolveMainTestClassNameTask
 					});
 	}
 
-	private static String getJavaApplicationMainClass(ExtensionContainer extensions) {
+	private static @Nullable String getJavaApplicationMainClass(ExtensionContainer extensions) {
 		JavaApplication javaApplication = extensions.findByType(JavaApplication.class);
 		if (javaApplication == null) {
 			return null;
@@ -200,10 +203,12 @@ private void configureArtifactPublication(TaskProvider<BootJar> bootJar) {
 	}
 
 	private void configureBootRunTask(Project project, TaskProvider<ResolveMainClassName> resolveMainClassName) {
-		Callable<FileCollection> classpath = () -> javaPluginExtension(project).getSourceSets()
-			.findByName(SourceSet.MAIN_SOURCE_SET_NAME)
-			.getRuntimeClasspath()
-			.filter(new JarTypeFileSpec());
+		Callable<FileCollection> classpath = () -> {
+			SourceSet mainSourceSet = javaPluginExtension(project).getSourceSets()
+				.findByName(SourceSet.MAIN_SOURCE_SET_NAME);
+			Assert.state(mainSourceSet != null, "'mainSourceSet' must not be null");
+			return mainSourceSet.getRuntimeClasspath().filter(new JarTypeFileSpec());
+		};
 		project.getTasks().register(SpringBootPlugin.BOOT_RUN_TASK_NAME, BootRun.class, (run) -> {
 			run.setDescription("Runs this project as a Spring Boot application.");
 			run.setGroup(ApplicationPlugin.APPLICATION_GROUP);
@@ -214,10 +219,12 @@ private void configureBootRunTask(Project project, TaskProvider<ResolveMainClass
 	}
 
 	private void configureBootTestRunTask(Project project, TaskProvider<ResolveMainClassName> resolveMainClassName) {
-		Callable<FileCollection> classpath = () -> javaPluginExtension(project).getSourceSets()
-			.findByName(SourceSet.TEST_SOURCE_SET_NAME)
-			.getRuntimeClasspath()
-			.filter(new JarTypeFileSpec());
+		Callable<FileCollection> classpath = () -> {
+			SourceSet testSourceSet = javaPluginExtension(project).getSourceSets()
+				.findByName(SourceSet.TEST_SOURCE_SET_NAME);
+			Assert.state(testSourceSet != null, "'testSourceSet' must not be null");
+			return testSourceSet.getRuntimeClasspath().filter(new JarTypeFileSpec());
+		};
 		project.getTasks().register("bootTestRun", BootRun.class, (run) -> {
 			run.setDescription("Runs this project as a Spring Boot application using the test runtime classpath.");
 			run.setGroup(ApplicationPlugin.APPLICATION_GROUP);

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/ResolveMainClassName.java

@@ -40,8 +40,10 @@
 import org.gradle.api.tasks.OutputFile;
 import org.gradle.api.tasks.TaskAction;
 import org.gradle.work.DisableCachingByDefault;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.boot.loader.tools.MainClassFinder;
+import org.springframework.util.Assert;
 
 /**
  * {@link Task} for resolving the name of the application's main class.
@@ -58,7 +60,7 @@ public class ResolveMainClassName extends DefaultTask {
 
 	private final Property<String> configuredMainClass;
 
-	private FileCollection classpath;
+	private @Nullable FileCollection classpath;
 
 	/**
 	 * Creates a new instance of the {@code ResolveMainClassName} task.
@@ -75,6 +77,7 @@ public ResolveMainClassName() {
 	 */
 	@Classpath
 	public FileCollection getClasspath() {
+		Assert.state(this.classpath != null, "'classpath' must not be null");
 		return this.classpath;
 	}
 
@@ -140,7 +143,7 @@ private String resolveMainClassName() {
 			.orElse("");
 	}
 
-	private String findMainClass(File file) {
+	private @Nullable String findMainClass(File file) {
 		try {
 			return MainClassFinder.findSingleMainClass(file, SPRING_BOOT_APPLICATION_CLASS_NAME);
 		}

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/SinglePublishedArtifact.java

@@ -24,6 +24,7 @@
 import org.gradle.api.tasks.TaskDependency;
 import org.gradle.api.tasks.TaskProvider;
 import org.gradle.api.tasks.bundling.Jar;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.boot.gradle.tasks.bundling.BootJar;
 import org.springframework.boot.gradle.tasks.bundling.BootWar;
@@ -41,7 +42,7 @@ final class SinglePublishedArtifact implements Buildable {
 
 	private final ArtifactHandler handler;
 
-	private PublishArtifact currentArtifact;
+	private @Nullable PublishArtifact currentArtifact;
 
 	SinglePublishedArtifact(Configuration configuration, ArtifactHandler handler) {
 		this.configuration = configuration;

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/SpringBootPlugin.java

@@ -23,6 +23,7 @@
 import org.gradle.api.Plugin;
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Configuration;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.boot.gradle.dsl.SpringBootExtension;
 import org.springframework.boot.gradle.tasks.bundling.BootBuildImage;
@@ -42,7 +43,8 @@
  */
 public class SpringBootPlugin implements Plugin<Project> {
 
-	private static final String SPRING_BOOT_VERSION = VersionExtractor.forClass(DependencyManagementPluginAction.class);
+	private static final @Nullable String SPRING_BOOT_VERSION = VersionExtractor
+		.forClass(DependencyManagementPluginAction.class);
 
 	/**
 	 * The name of the {@link Configuration} that contains Spring Boot archives.

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Central classes for the Spring Boot Gradle plugin.
  */
+@NullMarked
 package org.springframework.boot.gradle.plugin;
+
+import org.jspecify.annotations.NullMarked;

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/aot/ProcessTestAot.java

@@ -31,6 +31,9 @@
 import org.gradle.api.tasks.PathSensitivity;
 import org.gradle.api.tasks.SkipWhenEmpty;
 import org.gradle.api.tasks.TaskAction;
+import org.jspecify.annotations.Nullable;
+
+import org.springframework.util.Assert;
 
 /**
  * Custom {@link JavaExec} task for ahead-of-time processing of a Spring Boot
@@ -42,7 +45,7 @@
 @CacheableTask
 public class ProcessTestAot extends AbstractAot {
 
-	private FileCollection classpathRoots;
+	private @Nullable FileCollection classpathRoots;
 
 	public ProcessTestAot() {
 		getMainClass().set("org.springframework.boot.test.context.SpringBootTestAotProcessor");
@@ -54,7 +57,7 @@ public ProcessTestAot() {
 	 */
 	@InputFiles
 	@PathSensitive(PathSensitivity.RELATIVE)
-	public final FileCollection getClasspathRoots() {
+	public final @Nullable FileCollection getClasspathRoots() {
 		return this.classpathRoots;
 	}
 
@@ -71,14 +74,17 @@ public void setClasspathRoots(FileCollection classpathRoots) {
 	@IgnoreEmptyDirectories
 	@PathSensitive(PathSensitivity.RELATIVE)
 	final FileTree getInputClasses() {
+		Assert.state(this.classpathRoots != null, "'classpathRoots' must not be null");
 		return this.classpathRoots.getAsFileTree();
 	}
 
 	@Override
 	@TaskAction
 	public void exec() {
 		List<String> args = new ArrayList<>();
-		args.add(getClasspathRoots().getFiles()
+		FileCollection classpathRoots = getClasspathRoots();
+		Assert.state(classpathRoots != null, "'classpathRoots' must not be null");
+		args.add(classpathRoots.getFiles()
 			.stream()
 			.filter(File::exists)
 			.map(File::getAbsolutePath)

build-plugin/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/aot/package-info.java

@@ -17,4 +17,7 @@
 /**
  * Support for ahead-of-time processing of an application built with Gradle.
  */
+@NullMarked
 package org.springframework.boot.gradle.tasks.aot;
+
+import org.jspecify.annotations.NullMarked;