Remove classpath index manifest attribute from repackaged war files

Fixes gh-28895

spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/Layouts.java

@@ -29,6 +29,7 @@ import java.util.Map;
  * @author Dave Syer
  * @author Andy Wilkinson
  * @author Madhura Bhave
+ * @author Scott Frederick
  * @since 1.0.0
  */
 public final class Layouts {
@@ -160,11 +161,6 @@ public final class Layouts {
 			return "WEB-INF/classes/";
 		}
 
-		@Override
-		public String getClasspathIndexFileLocation() {
-			return "WEB-INF/classpath.idx";
-		}
-
 		@Override
 		public String getLayersIndexFileLocation() {
 			return "WEB-INF/layers.idx";

spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/Packager.java

@@ -510,15 +510,15 @@ public abstract class Packager {
 					writtenPaths.add(path);
 				}
 			}
-			if (getLayout() instanceof RepackagingLayout) {
-				writeClasspathIndex(writtenPaths, (RepackagingLayout) getLayout(), writer);
-			}
+			writeClasspathIndexIfNecessary(writtenPaths, getLayout(), writer);
 		}
 
-		private void writeClasspathIndex(List<String> paths, RepackagingLayout layout, AbstractJarWriter writer)
+		private void writeClasspathIndexIfNecessary(List<String> paths, Layout layout, AbstractJarWriter writer)
 				throws IOException {
-			List<String> names = paths.stream().map((path) -> "- \"" + path + "\"").collect(Collectors.toList());
-			writer.writeIndexFile(layout.getClasspathIndexFileLocation(), names);
+			if (layout.getClasspathIndexFileLocation() != null) {
+				List<String> names = paths.stream().map((path) -> "- \"" + path + "\"").collect(Collectors.toList());
+				writer.writeIndexFile(layout.getClasspathIndexFileLocation(), names);
+			}
 		}
 
 		private class PackagedLibrariesUnpackHandler implements UnpackHandler {

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/java/org/springframework/boot/maven/AbstractArchiveIntegrationTests.java

@@ -43,6 +43,7 @@ import static org.assertj.core.api.Assertions.contentOf;
  * Base class for archive (jar or war) related Maven plugin integration tests.
  *
  * @author Andy Wilkinson
+ * @author Scott Frederick
  */
 abstract class AbstractArchiveIntegrationTests {
 
@@ -201,6 +202,11 @@ abstract class AbstractArchiveIntegrationTests {
 				return this;
 			}
 
+			ManifestAssert doesNotHaveAttribute(String name) {
+				assertThat(this.actual.getMainAttributes().getValue(name)).isNull();
+				return this;
+			}
+
 		}
 
 	}

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/java/org/springframework/boot/maven/JarIntegrationTests.java

@@ -38,6 +38,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  *
  * @author Andy Wilkinson
  * @author Madhura Bhave
+ * @author Scott Frederick
  */
 @ExtendWith(MavenBuildExtension.class)
 class JarIntegrationTests extends AbstractArchiveIntegrationTests {
@@ -363,6 +364,16 @@ class JarIntegrationTests extends AbstractArchiveIntegrationTests {
 		});
 	}
 
+	@TestTemplate
+	void repackagedJarContainsClasspathIndex(MavenBuild mavenBuild) {
+		mavenBuild.project("jar").execute((project) -> {
+			File repackaged = new File(project, "target/jar-0.0.1.BUILD-SNAPSHOT.jar");
+			assertThat(jar(repackaged)).manifest(
+					(manifest) -> manifest.hasAttribute("Spring-Boot-Classpath-Index", "BOOT-INF/classpath.idx"));
+			assertThat(jar(repackaged)).hasEntryWithName("BOOT-INF/classpath.idx");
+		});
+	}
+
 	@TestTemplate
 	void whenJarIsRepackagedWithOutputTimestampConfiguredThenJarIsReproducible(MavenBuild mavenBuild)
 			throws InterruptedException {

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/intTest/java/org/springframework/boot/maven/WarIntegrationTests.java

@@ -38,6 +38,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Integration tests for the Maven plugin's war support.
  *
  * @author Andy Wilkinson
+ * @author Scott Frederick
  */
 @ExtendWith(MavenBuildExtension.class)
 class WarIntegrationTests extends AbstractArchiveIntegrationTests {
@@ -190,6 +191,16 @@ class WarIntegrationTests extends AbstractArchiveIntegrationTests {
 		});
 	}
 
+	@TestTemplate
+	void repackagedWarDoesNotContainClasspathIndex(MavenBuild mavenBuild) {
+		mavenBuild.project("war").execute((project) -> {
+			File repackaged = new File(project, "target/war-0.0.1.BUILD-SNAPSHOT.war");
+			assertThat(jar(repackaged))
+					.manifest((manifest) -> manifest.doesNotHaveAttribute("Spring-Boot-Classpath-Index"));
+			assertThat(jar(repackaged)).doesNotHaveEntryWithName("BOOT-INF/classpath.idx");
+		});
+	}
+
 	@TestTemplate
 	void whenEntryIsExcludedItShouldNotBePresentInTheRepackagedWar(MavenBuild mavenBuild) {
 		mavenBuild.project("war-exclude-entry").execute((project) -> {