Automatically create developmentOnly configuration

Previously, the developmentOnly configuration, typically used for
Devtools, had to be declared manually. The BootJar and BootWar tasks
then had a property, excludeDevtools, that could be used to control
whether or not Devtools would be excluded from the executable archive.

This commit updates the reaction to the Java plugin being applied to
automatically create the developmentOnly configuration. The classpaths
of bootJar and bootWar are then configured not to include the contents
of the developmentOnly configuration. As a result of this, the
excludeDevtools property is no longer needed and has been deprecated.
Its default has also been changed from true to false to make it easy
to opt in to Devtools, when configured as a development-only
dependency, being included in executable jars and wars by adding
developmentOnly to the classpath of the archive task.

Closes gh-16599

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

@@ -27,6 +27,7 @@ import org.gradle.api.Action;
 import org.gradle.api.Plugin;
 import org.gradle.api.Project;
 import org.gradle.api.Task;
+import org.gradle.api.artifacts.Configuration;
 import org.gradle.api.file.FileCollection;
 import org.gradle.api.internal.artifacts.dsl.LazyPublishArtifact;
 import org.gradle.api.plugins.ApplicationPlugin;
@@ -67,6 +68,7 @@ final class JavaPluginAction implements PluginApplicationAction {
 	public void execute(Project project) {
 		disableJarTask(project);
 		configureBuildTask(project);
+		configureDevelopmentOnlyConfiguration(project);
 		TaskProvider<BootJar> bootJar = configureBootJarTask(project);
 		configureBootBuildImageTask(project, bootJar);
 		configureArtifactPublication(bootJar);
@@ -92,7 +94,8 @@ final class JavaPluginAction implements PluginApplicationAction {
 			bootJar.setGroup(BasePlugin.BUILD_GROUP);
 			SourceSet mainSourceSet = javaPluginConvention(project).getSourceSets()
 					.getByName(SourceSet.MAIN_SOURCE_SET_NAME);
-			bootJar.classpath((Callable<FileCollection>) mainSourceSet::getRuntimeClasspath);
+			bootJar.classpath((Callable<FileCollection>) () -> mainSourceSet.getRuntimeClasspath().minus(
+					project.getConfigurations().getByName(SpringBootPlugin.DEVELOPMENT_ONLY_CONFIGURATION_NAME)));
 			bootJar.conventionMapping("mainClassName", new MainClassConvention(project, bootJar::getClasspath));
 		});
 	}
@@ -157,6 +160,15 @@ final class JavaPluginAction implements PluginApplicationAction {
 		compile.doFirst(new AdditionalMetadataLocationsConfigurer());
 	}
 
+	private void configureDevelopmentOnlyConfiguration(Project project) {
+		Configuration developmentOnly = project.getConfigurations()
+				.create(SpringBootPlugin.DEVELOPMENT_ONLY_CONFIGURATION_NAME);
+		developmentOnly
+				.setDescription("Configuration for development-only dependencies such as Spring Boot's DevTools.");
+		project.getConfigurations().getByName(JavaPlugin.RUNTIME_CLASSPATH_CONFIGURATION_NAME)
+				.extendsFrom(developmentOnly);
+	}
+
 	/**
 	 * Task {@link Action} to add additional meta-data locations. We need to use an
 	 * inner-class rather than a lambda due to

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

@@ -70,6 +70,12 @@ public class SpringBootPlugin implements Plugin<Project> {
 	 */
 	public static final String BOOT_BUILD_IMAGE_TASK_NAME = "bootBuildImage";
 
+	/**
+	 * The name of the {@code developmentOnly} configuration.
+	 * @since 2.3.0
+	 */
+	public static final String DEVELOPMENT_ONLY_CONFIGURATION_NAME = "developmentOnly";
+
 	/**
 	 * The coordinates {@code (group:name:version)} of the
 	 * {@code spring-boot-dependencies} bom.

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/plugin/WarPluginAction.java

@@ -19,7 +19,8 @@ package org.springframework.boot.gradle.plugin;
 import org.gradle.api.Action;
 import org.gradle.api.Plugin;
 import org.gradle.api.Project;
-import org.gradle.api.artifacts.Configuration;
+import org.gradle.api.artifacts.ConfigurationContainer;
+import org.gradle.api.file.FileCollection;
 import org.gradle.api.internal.artifacts.dsl.LazyPublishArtifact;
 import org.gradle.api.plugins.BasePlugin;
 import org.gradle.api.plugins.WarPlugin;
@@ -63,12 +64,15 @@ class WarPluginAction implements PluginApplicationAction {
 			bootWar.setDescription("Assembles an executable war archive containing webapp"
 					+ " content, and the main classes and their dependencies.");
 			bootWar.providedClasspath(providedRuntimeConfiguration(project));
+			bootWar.setClasspath(bootWar.getClasspath().minus(
+					project.getConfigurations().getByName(SpringBootPlugin.DEVELOPMENT_ONLY_CONFIGURATION_NAME)));
 			bootWar.conventionMapping("mainClassName", new MainClassConvention(project, bootWar::getClasspath));
 		});
 	}
 
-	private Configuration providedRuntimeConfiguration(Project project) {
-		return project.getConfigurations().getByName(WarPlugin.PROVIDED_RUNTIME_CONFIGURATION_NAME);
+	private FileCollection providedRuntimeConfiguration(Project project) {
+		ConfigurationContainer configurations = project.getConfigurations();
+		return configurations.getByName(WarPlugin.PROVIDED_RUNTIME_CONFIGURATION_NAME);
 	}
 
 	private void configureArtifactPublication(TaskProvider<BootWar> bootWar) {

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/BootArchive.java

@@ -118,15 +118,21 @@ public interface BootArchive extends Task {
 	 * {@code false}.
 	 * @return {@code true} if the Devtools jar should be excluded, or {@code false} if
 	 * not
+	 * @deprecated since 2.3.0 in favour of configuring a classpath that does not include
+	 * development-only dependencies
 	 */
 	@Input
+	@Deprecated
 	boolean isExcludeDevtools();
 
 	/**
 	 * Sets whether or not the Devtools jar should be excluded.
 	 * @param excludeDevtools {@code true} if the Devtools jar should be excluded, or
 	 * {@code false} if not
+	 * @deprecated since 2.3.0 in favour of configuring a classpath that does not include
+	 * development-only dependencies
 	 */
+	@Deprecated
 	void setExcludeDevtools(boolean excludeDevtools);
 
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/main/java/org/springframework/boot/gradle/tasks/bundling/BootArchiveSupport.java

@@ -76,7 +76,7 @@ class BootArchiveSupport {
 
 	private LaunchScriptConfiguration launchScript;
 
-	private boolean excludeDevtools = true;
+	private boolean excludeDevtools = false;
 
 	BootArchiveSupport(String loaderMainClass, Spec<FileCopyDetails> librarySpec,
 			Function<FileCopyDetails, ZipCompression> compressionResolver) {