fix lint

diff.go

@@ -188,13 +188,9 @@ func diffNodes(nodes1 []*Node, nodes2 []*Node) ([]*Node, []*Node) {
 		node2 := nodes2[i2]
 		switch bytes.Compare(node1.key, node2.key) {
 		case 0:
-			if node1.version == node2.version {
-				// we assume they are the same nodes without comparing hashes,
-				// since they have the same (height, key, version).
-				if bytes.Compare(nodes1[i1].hash, nodes2[i2].hash) != 0 {
-					panic("invariant")
-				}
-			} else {
+			// we assume they are the same nodes without comparing hashes
+			// if they have the same (height, key, version).
+			if node1.version != node2.version {
 				// overridden by same key
 				orphaned = append(orphaned, node1)
 				new = append(new, node2)

nodedb.go

@@ -392,8 +392,10 @@ func (ndb *nodeDB) resetBatch() error {
 	return nil
 }
 
-// Contract: successor must exists, predecessor can be 0 if don't exists.
-// calls deleteOrphans, deleteRoot
+// Contract:
+// - successor must exists, predecessor can be 0 if don't exists.
+// - predecessor < version < successor
+// - no other versions between predecessor, version, successor
 func (ndb *nodeDB) deleteVersion(version, predecessor, successor int64) error {
 	if err := ndb.deleteOrphans(version, predecessor, successor); err != nil {
 		return err
@@ -471,7 +473,9 @@ func (ndb *nodeDB) rollbackVersion(version, predecessor int64) error {
 			stack = append(stack, node.rightHash, node.leftHash)
 		}
 	}
-	ndb.batch.Delete(ndb.rootKey(version))
+	if err := ndb.batch.Delete(ndb.rootKey(version)); err != nil {
+		return err
+	}
 	return nil
 }
 
@@ -605,8 +609,10 @@ func (ndb *nodeDB) DeleteFastNode(key []byte) error {
 }
 
 // deleteOrphans deletes orphaned nodes from disk by comparing the related versions.
-// Contract: predecessor < version < successor, and there's no other version in between.
-//           predecessor could be 0 if don't exists, successor must exist.
+// Contract:
+// - predecessor < version < successor
+// - there's no other version in between
+// - predecessor could be 0 if don't exists, successor must exist.
 func (ndb *nodeDB) deleteOrphans(version, predecessor, successor int64) error {
 	var (
 		root1, root2 *Node
@@ -730,22 +736,6 @@ func (ndb *nodeDB) getNextVersion(version int64) (int64, error) {
 	return 0, nil
 }
 
-// deleteRoot deletes the root entry from disk, but not the node it points to.
-func (ndb *nodeDB) deleteRoot(version int64, checkLatestVersion bool) error {
-	latestVersion, err := ndb.getLatestVersion()
-	if err != nil {
-		return err
-	}
-
-	if checkLatestVersion && version == latestVersion {
-		return errors.New("tried to delete latest version")
-	}
-	if err := ndb.batch.Delete(ndb.rootKey(version)); err != nil {
-		return err
-	}
-	return nil
-}
-
 // Traverse fast nodes and return error if any, nil otherwise
 func (ndb *nodeDB) traverseFastNodes(fn func(k, v []byte) error) error {
 	return ndb.traversePrefix(fastKeyFormat.Key(), fn)