Merge pull request #843 from nuttycom/wallet/not_yet_fetched_memo

Update memo retrieval API to reflect that memos may not be present.

zcash_client_backend/CHANGELOG.md

@@ -8,6 +8,9 @@ and this library adheres to Rust's notion of
 ## [Unreleased]
 ### Changed
 - Bumped dependencies to `hdwallet 0.4`.
+- `WalletRead::get_memo` now returns `Result<Option<Memo>, Self::Error>`
+  instead of `Result<Memo, Self::Error>` in order to make representable
+  wallet states where the full note plaintext is not available.
 
 ## [0.9.0] - 2023-04-28
 ### Added
@@ -19,7 +22,7 @@ and this library adheres to Rust's notion of
   to allow reuse of the data structure for non-Sapling contexts.
 - `data_api::SentTransactionOutput` must now be constructed using
   `SentTransactionOutput::from_parts`. The internal state of `SentTransactionOutput`
-  is now private, and accessible via methods that have the same names as the 
+  is now private, and accessible via methods that have the same names as the
   previously exposed fields.
 
 ### Renamed

zcash_client_backend/src/data_api.rs

@@ -155,8 +155,10 @@ pub trait WalletRead {
     /// Returns the memo for a note.
     ///
     /// Implementations of this method must return an error if the note identifier
-    /// does not appear in the backing data store.
-    fn get_memo(&self, id_note: Self::NoteRef) -> Result<Memo, Self::Error>;
+    /// does not appear in the backing data store. Returns `Ok(None)` if the note
+    /// is known to the wallet but memo data has not yet been populated for that
+    /// note.
+    fn get_memo(&self, id_note: Self::NoteRef) -> Result<Option<Memo>, Self::Error>;
 
     /// Returns a transaction.
     fn get_transaction(&self, id_tx: Self::TxRef) -> Result<Transaction, Self::Error>;
@@ -512,8 +514,8 @@ pub mod testing {
             Ok(Amount::zero())
         }
 
-        fn get_memo(&self, _id_note: Self::NoteRef) -> Result<Memo, Self::Error> {
-            Ok(Memo::Empty)
+        fn get_memo(&self, _id_note: Self::NoteRef) -> Result<Option<Memo>, Self::Error> {
+            Ok(None)
         }
 
         fn get_transaction(&self, _id_tx: Self::TxRef) -> Result<Transaction, Self::Error> {

zcash_client_sqlite/src/lib.rs

@@ -190,7 +190,7 @@ impl<P: consensus::Parameters> WalletRead for WalletDb<P> {
         wallet::get_transaction(self, id_tx)
     }
 
-    fn get_memo(&self, id_note: Self::NoteRef) -> Result<Memo, Self::Error> {
+    fn get_memo(&self, id_note: Self::NoteRef) -> Result<Option<Memo>, Self::Error> {
         match id_note {
             NoteId::SentNoteId(id_note) => wallet::get_sent_memo(self, id_note),
             NoteId::ReceivedNoteId(id_note) => wallet::get_received_memo(self, id_note),
@@ -349,7 +349,7 @@ impl<'a, P: consensus::Parameters> WalletRead for DataConnStmtCache<'a, P> {
         self.wallet_db.get_transaction(id_tx)
     }
 
-    fn get_memo(&self, id_note: Self::NoteRef) -> Result<Memo, Self::Error> {
+    fn get_memo(&self, id_note: Self::NoteRef) -> Result<Option<Memo>, Self::Error> {
         self.wallet_db.get_memo(id_note)
     }
 

zcash_client_sqlite/src/wallet.rs

@@ -480,17 +480,21 @@ pub(crate) fn get_balance_at<P>(
 pub(crate) fn get_received_memo<P>(
     wdb: &WalletDb<P>,
     id_note: i64,
-) -> Result<Memo, SqliteClientError> {
-    let memo_bytes: Vec<_> = wdb.conn.query_row(
+) -> Result<Option<Memo>, SqliteClientError> {
+    let memo_bytes: Option<Vec<_>> = wdb.conn.query_row(
         "SELECT memo FROM sapling_received_notes
         WHERE id_note = ?",
         [id_note],
         |row| row.get(0),
     )?;
 
-    MemoBytes::from_bytes(&memo_bytes)
-        .and_then(Memo::try_from)
-        .map_err(SqliteClientError::from)
+    memo_bytes
+        .map(|b| {
+            MemoBytes::from_bytes(&b)
+                .and_then(Memo::try_from)
+                .map_err(SqliteClientError::from)
+        })
+        .transpose()
 }
 
 /// Looks up a transaction by its internal database identifier.
@@ -519,17 +523,24 @@ pub(crate) fn get_transaction<P: Parameters>(
 ///
 /// The note is identified by its row index in the `sent_notes` table within the wdb
 /// database.
-pub(crate) fn get_sent_memo<P>(wdb: &WalletDb<P>, id_note: i64) -> Result<Memo, SqliteClientError> {
-    let memo_bytes: Vec<_> = wdb.conn.query_row(
+pub(crate) fn get_sent_memo<P>(
+    wdb: &WalletDb<P>,
+    id_note: i64,
+) -> Result<Option<Memo>, SqliteClientError> {
+    let memo_bytes: Option<Vec<_>> = wdb.conn.query_row(
         "SELECT memo FROM sent_notes
         WHERE id_note = ?",
         [id_note],
         |row| row.get(0),
     )?;
 
-    MemoBytes::from_bytes(&memo_bytes)
-        .and_then(Memo::try_from)
-        .map_err(SqliteClientError::from)
+    memo_bytes
+        .map(|b| {
+            MemoBytes::from_bytes(&b)
+                .and_then(Memo::try_from)
+                .map_err(SqliteClientError::from)
+        })
+        .transpose()
 }
 
 /// Returns the minimum and maximum heights for blocks stored in the wallet database.