fix: make LazyLoadVersion possible to load empty root

mutable_tree.go

@@ -323,7 +323,11 @@ func (tree *MutableTree) LazyLoadVersion(targetVersion int64) (int64, error) {
  iTree := &ImmutableTree{
  ndb: tree.ndb,
  version: targetVersion,
- root: tree.ndb.GetNode(rootHash),
+ }
+ if len(rootHash) > 0 {
+ // If rootHash is empty then root of tree should be nil
+ // This makes `LazyLoadVersion` to do the same thing as `LoadVersion`
+ iTree.root = tree.ndb.GetNode(rootHash)
  }
 
  tree.orphans = map[string]int64{}

mutable_tree_test.go

@@ -358,3 +358,25 @@ func TestMutableTree_DeleteVersion(t *testing.T) {
  // cannot delete latest version
  require.Error(t, tree.DeleteVersion(2))
 }
+
+func TestMutableTree_LazyLoadVersionWithEmptyTree(t *testing.T) {
+ mdb := db.NewMemDB()
+ tree, err := NewMutableTree(mdb, 1000)
+ require.NoError(t, err)
+ _, v1, err := tree.SaveVersion()
+ require.NoError(t, err)
+
+ newTree1, err := NewMutableTree(mdb, 1000)
+ require.NoError(t, err)
+ v2, err := newTree1.LazyLoadVersion(1)
+ require.NoError(t, err)
+ require.True(t, v1 == v2)
+
+ newTree2, err := NewMutableTree(mdb, 1000)
+ require.NoError(t, err)
+ v2, err = newTree1.LoadVersion(1)
+ require.NoError(t, err)
+ require.True(t, v1 == v2)
+
+ require.True(t, newTree1.root == newTree2.root)
+}