Include library resources on classpath of AOT source generation

Closes gh-31803

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

@@ -22,6 +22,7 @@ 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.attributes.LibraryElements;
 import org.gradle.api.file.Directory;
 import org.gradle.api.plugins.JavaPlugin;
 import org.gradle.api.plugins.JavaPluginExtension;
@@ -75,6 +76,9 @@ public class SpringBootAotPlugin implements Plugin<Project> {
 			Configuration aotImplementation = configurations.getByName(aot.getImplementationConfigurationName());
 			aotImplementation.extendsFrom(configurations.getByName(main.getImplementationConfigurationName()));
 			aotImplementation.extendsFrom(configurations.getByName(main.getRuntimeOnlyConfigurationName()));
+			configurations.getByName(aot.getCompileClasspathConfigurationName())
+					.attributes((attributes) -> attributes.attribute(LibraryElements.LIBRARY_ELEMENTS_ATTRIBUTE,
+							project.getObjects().named(LibraryElements.class, LibraryElements.CLASSES_AND_RESOURCES)));
 		});
 		return aotSourceSet;
 	}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/plugin/SpringBootAotPluginIntegrationTests.java

@@ -16,6 +16,11 @@
 
 package org.springframework.boot.gradle.plugin;
 
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.util.List;
+
 import org.junit.jupiter.api.TestTemplate;
 
 import org.springframework.boot.gradle.junit.GradleCompatibility;
@@ -45,4 +50,14 @@ class SpringBootAotPluginIntegrationTests {
 				.contains("generateAotSources exists = true");
 	}
 
+	@TestTemplate
+	void generateAotSourcesHasLibraryResourcesOnItsClasspath() throws IOException {
+		File settings = new File(this.gradleBuild.getProjectDir(), "settings.gradle");
+		Files.write(settings.toPath(), List.of("include 'library'"));
+		File library = new File(this.gradleBuild.getProjectDir(), "library");
+		library.mkdirs();
+		Files.write(library.toPath().resolve("build.gradle"), List.of("plugins {", "    id 'java-library'", "}"));
+		assertThat(this.gradleBuild.build("generateAotSourcesClasspath").getOutput()).contains("library.jar");
+	}
+
 }

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/resources/org/springframework/boot/gradle/plugin/SpringBootAotPluginIntegrationTests-generateAotSourcesHasLibraryResourcesOnItsClasspath.gradle

@@ -0,0 +1,15 @@
+plugins {
+	id 'org.springframework.boot'
+	id 'org.springframework.boot.aot'
+	id 'java'
+}
+
+dependencies {
+	implementation project(":library")
+}
+
+task('generateAotSourcesClasspath') {
+	doFirst {
+		tasks.findByName('generateAotSources').classpath.files.each { println it }
+	}
+}