fix bug where empty content directories were being created

ocfl-java-core/src/main/java/edu/wisc/library/ocfl/core/DefaultOcflRepository.java

@@ -604,6 +604,13 @@ private void getObjectInternal(Inventory inventory, VersionNum versionNum, Path
 
     protected void writeNewVersion(Inventory inventory, Path stagingDir) {
         var finalInventory = writeInventory(inventory, stagingDir);
+
+        // Versions should not contain empty content directories
+        var contentDir = stagingDir.resolve(inventory.resolveContentDirectory());
+        if (!FileUtil.hasChildren(contentDir)) {
+            UncheckedFiles.delete(contentDir);
+        }
+
         objectLock.doInWriteLock(inventory.getId(), () -> storage.storeNewVersion(finalInventory, stagingDir));
     }
 

ocfl-java-core/src/main/java/edu/wisc/library/ocfl/core/storage/filesystem/FileSystemOcflStorage.java

@@ -866,7 +866,15 @@ private void verifyPriorInventory(Inventory inventory, Path sidecarPath) {
         }
     }
 
-    private void versionContentCheck(Inventory inventory, ObjectPaths.ObjectRoot objectRoot, Path contentPath, boolean checkFixity) {
+    private void versionContentCheck(Inventory inventory,
+                                     ObjectPaths.ObjectRoot objectRoot,
+                                     Path contentPath,
+                                     boolean checkFixity) {
+        // The content directory will not exist if the version does not introduce new files
+        if (Files.notExists(contentPath)) {
+            return;
+        }
+
         var version = inventory.getHeadVersion();
         var fileIds = inventory.getFileIdsForMatchingFiles(objectRoot.path().relativize(contentPath));
 

ocfl-java-core/src/main/java/edu/wisc/library/ocfl/core/util/FileUtil.java

@@ -262,7 +262,6 @@ public static void safeDeleteDirectory(Path path) {
         }
     }
 
-
     /**
      * Recursive delete that deletes everything under and including the specified directory. Failures deleting individual
      * files are logged and a single exception is thrown at the end.

ocfl-java-itest/src/test/java/edu/wisc/library/ocfl/itest/filesystem/FileSystemOcflITest.java

@@ -8,13 +8,16 @@
 import edu.wisc.library.ocfl.core.cache.NoOpCache;
 import edu.wisc.library.ocfl.core.extension.UnsupportedExtensionBehavior;
 import edu.wisc.library.ocfl.core.extension.storage.layout.HashedNTupleLayoutExtension;
+import edu.wisc.library.ocfl.core.extension.storage.layout.config.FlatLayoutConfig;
 import edu.wisc.library.ocfl.core.extension.storage.layout.config.HashedNTupleIdEncapsulationLayoutConfig;
 import edu.wisc.library.ocfl.core.extension.storage.layout.config.HashedNTupleLayoutConfig;
 import edu.wisc.library.ocfl.core.util.FileUtil;
 import edu.wisc.library.ocfl.core.util.UncheckedFiles;
 import edu.wisc.library.ocfl.itest.ITestHelper;
 import edu.wisc.library.ocfl.itest.OcflITest;
 import edu.wisc.library.ocfl.test.TestHelper;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.Matchers;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.EnabledOnOs;
 import org.junit.jupiter.api.condition.OS;
@@ -39,6 +42,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsInAnyOrder;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 
 public class FileSystemOcflITest extends OcflITest {
 
@@ -166,6 +170,27 @@ public void allowPathsWithDifficultCharsWhenNoRestrictionsApplied() throws IOExc
         }
     }
 
+    @Test
+    public void shouldNotCreateEmptyContentDirWhenVersionHasNoContent() {
+        var repoName = "empty-content";
+        var repo = defaultRepo(repoName, builder -> builder.defaultLayoutConfig(new FlatLayoutConfig()));
+
+        var objectId = "object";
+
+        repo.updateObject(ObjectVersionId.head(objectId), null, updater -> {
+            updater.writeFile(streamString("asdf"), "file.txt");
+        });
+
+        repo.updateObject(ObjectVersionId.head(objectId), null, updater -> {
+            updater.removeFile("file.txt");
+        });
+
+        var root = repoDir(repoName);
+        var v2ContentPath = root.resolve(objectId).resolve("v2/content");
+
+        assertFalse(Files.exists(v2ContentPath), "empty content directories should not exist");
+    }
+
     @Override
     protected void onBefore() {
         reposDir = UncheckedFiles.createDirectories(tempRoot.resolve("repos"));