Ensure LayoutFactory is not passed an empty file

Update `Repackager` to ensure that `getLayout` is called before we
backup the source file. This restores earlier behavior that some
custom `ModuleFactory` implementations were relying on.

Closes gh-22995

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

@@ -101,6 +101,7 @@ public class Repackager extends Packager {
 	public void repackage(File destination, Libraries libraries, LaunchScript launchScript, FileTime lastModifiedTime)
 			throws IOException {
 		Assert.isTrue(destination != null && !destination.isDirectory(), "Invalid destination");
+		getLayout(); // get layout early
 		if (lastModifiedTime != null && getLayout() instanceof War) {
 			throw new IllegalStateException("Reproducible repackaging is not supported with war packaging");
 		}

spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/test/java/org/springframework/boot/loader/tools/RepackagerTests.java

@@ -139,6 +139,15 @@ class RepackagerTests extends AbstractPackagerTests<Repackager> {
 		assertThat(hasLauncherClasses(this.destination)).isTrue();
 	}
 
+	@Test
+	void layoutFactoryGetsOriginalFile() throws Exception {
+		this.testJarFile.addClass("a/b/C.class", ClassWithMainMethod.class);
+		Repackager repackager = createRepackager(this.testJarFile.getFile(), false);
+		repackager.setLayoutFactory(new TestLayoutFactory());
+		repackager.repackage(this.destination, NO_LIBRARIES);
+		assertThat(hasLauncherClasses(this.destination)).isTrue();
+	}
+
 	@Test
 	void addLauncherScript() throws Exception {
 		this.testJarFile.addClass("a/b/C.class", ClassWithMainMethod.class);
@@ -266,4 +275,14 @@ class RepackagerTests extends AbstractPackagerTests<Repackager> {
 
 	}
 
+	static class TestLayoutFactory implements LayoutFactory {
+
+		@Override
+		public Layout getLayout(File source) {
+			assertThat(source.length()).isGreaterThan(0);
+			return new DefaultLayoutFactory().getLayout(source);
+		}
+
+	}
+
 }