From 5f1d75937b84cdc51ad81d7eb2a9b0123c57af3e Mon Sep 17 00:00:00 2001
From: Kris Nuttycombe <kris@nutty.land>
Date: Tue, 19 Mar 2024 17:15:06 -0600
Subject: [PATCH] zcash_client_backend: Treat protobuf default as the empty
 tree.

Fixes #1280
---
 zcash_client_backend/src/proto.rs | 44 +++++++++++++++++++------------
 1 file changed, 27 insertions(+), 17 deletions(-)

diff --git a/zcash_client_backend/src/proto.rs b/zcash_client_backend/src/proto.rs
index 3e58bc309..f9706c08b 100644
--- a/zcash_client_backend/src/proto.rs
+++ b/zcash_client_backend/src/proto.rs
@@ -263,15 +263,19 @@ impl service::TreeState {
     pub fn sapling_tree(
         &self,
     ) -> io::Result<CommitmentTree<Node, { sapling::NOTE_COMMITMENT_TREE_DEPTH }>> {
-        let sapling_tree_bytes = hex::decode(&self.sapling_tree).map_err(|e| {
-            io::Error::new(
-                io::ErrorKind::InvalidData,
-                format!("Hex decoding of Sapling tree bytes failed: {:?}", e),
+        if self.sapling_tree.is_empty() {
+            Ok(CommitmentTree::empty())
+        } else {
+            let sapling_tree_bytes = hex::decode(&self.sapling_tree).map_err(|e| {
+                io::Error::new(
+                    io::ErrorKind::InvalidData,
+                    format!("Hex decoding of Sapling tree bytes failed: {:?}", e),
+                )
+            })?;
+            read_commitment_tree::<Node, _, { sapling::NOTE_COMMITMENT_TREE_DEPTH }>(
+                &sapling_tree_bytes[..],
             )
-        })?;
-        read_commitment_tree::<Node, _, { sapling::NOTE_COMMITMENT_TREE_DEPTH }>(
-            &sapling_tree_bytes[..],
-        )
+        }
     }
 
     /// Deserializes and returns the Sapling note commitment tree field of the tree state.
@@ -280,15 +284,21 @@ impl service::TreeState {
         &self,
     ) -> io::Result<CommitmentTree<MerkleHashOrchard, { orchard::NOTE_COMMITMENT_TREE_DEPTH as u8 }>>
     {
-        let orchard_tree_bytes = hex::decode(&self.orchard_tree).map_err(|e| {
-            io::Error::new(
-                io::ErrorKind::InvalidData,
-                format!("Hex decoding of Orchard tree bytes failed: {:?}", e),
-            )
-        })?;
-        read_commitment_tree::<MerkleHashOrchard, _, { orchard::NOTE_COMMITMENT_TREE_DEPTH as u8 }>(
-            &orchard_tree_bytes[..],
-        )
+        if self.orchard_tree.is_empty() {
+            Ok(CommitmentTree::empty())
+        } else {
+            let orchard_tree_bytes = hex::decode(&self.orchard_tree).map_err(|e| {
+                io::Error::new(
+                    io::ErrorKind::InvalidData,
+                    format!("Hex decoding of Orchard tree bytes failed: {:?}", e),
+                )
+            })?;
+            read_commitment_tree::<
+                MerkleHashOrchard,
+                _,
+                { orchard::NOTE_COMMITMENT_TREE_DEPTH as u8 },
+            >(&orchard_tree_bytes[..])
+        }
     }
 
     /// Parses this tree state into a [`ChainState`] for use with [`scan_cached_blocks`].