Update mt.Delete for empty Tree cases

merkletree.go

@@ -310,7 +310,7 @@ func (mt *MerkleTree) Delete(k *big.Int) error {
 		}
 		switch n.Type {
 		case NodeTypeEmpty:
-			return nil
+			return ErrKeyNotFound
 		case NodeTypeLeaf:
 			if bytes.Equal(kHash[:], n.Entry[0][:]) {
 				// remove and go up with the sibling
@@ -337,6 +337,12 @@ func (mt *MerkleTree) Delete(k *big.Int) error {
 
 // rmAndUpload removes the key, and goes up until the root updating all the nodes with the new values.
 func (mt *MerkleTree) rmAndUpload(tx db.Tx, path []bool, kHash *Hash, siblings []*Hash) error {
+	if len(siblings) == 0 {
+		mt.rootKey = &HashZero
+		mt.dbInsert(tx, rootNodeValue, DBEntryTypeRoot, mt.rootKey[:])
+		return tx.Commit()
+	}
+
 	toUpload := siblings[len(siblings)-1]
 	if len(siblings) < 2 {
 		mt.rootKey = siblings[0]

merkletree_test.go

@@ -315,6 +315,12 @@ func TestDelete(t *testing.T) {
 	// mt.PrintGraphViz(nil)
 	assert.Nil(t, err)
 	assert.Equal(t, "12820263606494630162816839760750120928463716794691735985748071431547370997091", mt.Root().BigInt().String())
+
+	err = mt.Delete(big.NewInt(1234))
+	assert.Nil(t, err)
+	err = mt.Delete(big.NewInt(1))
+	assert.Nil(t, err)
+	assert.Equal(t, "0", mt.Root().String())
 }
 
 func TestDelete2(t *testing.T) {
@@ -420,3 +426,26 @@ func TestDelete5(t *testing.T) {
 	assert.Nil(t, err)
 	assert.Equal(t, mt2.Root(), mt.Root())
 }
+
+func TestDeleteNonExistingKeys(t *testing.T) {
+	mt, err := NewMerkleTree(db.NewMemoryStorage(), 10)
+	assert.Nil(t, err)
+
+	err = mt.Add(big.NewInt(1), big.NewInt(2))
+	assert.Nil(t, err)
+	err = mt.Add(big.NewInt(33), big.NewInt(44))
+	assert.Nil(t, err)
+
+	err = mt.Delete(big.NewInt(33))
+	assert.Nil(t, err)
+	err = mt.Delete(big.NewInt(33))
+	assert.Equal(t, ErrKeyNotFound, err)
+
+	err = mt.Delete(big.NewInt(1))
+	assert.Nil(t, err)
+
+	assert.Equal(t, "0", mt.Root().String())
+
+	err = mt.Delete(big.NewInt(33))
+	assert.Equal(t, ErrKeyNotFound, err)
+}