feat!: Support persistent UTXO locking

New APIs added for locking and unlocking a UTXO by outpoint
and to query the locked outpoints. Locking an outpoint
means that it is excluded from coin selection.

- Add `Wallet::lock_outpoint`
- Add `Wallet::unlock_outpoint`
- Add `Wallet::is_outpoint_locked`
- Add `Wallet::list_locked_outpoints`
- Add `Wallet::list_locked_unspent`

`test_lock_outpoint_persist` tests the lock/unlock
functionality and that the lock status is persistent.

BREAKING: Added `locked_outpoints` member field to ChangeSet.
A SQLite migration is included for adding the locked outpoints table.

Author: ValuedMammal

clippy.toml

@@ -1,4 +1 @@
-# TODO fix, see: https://rust-lang.github.io/rust-clippy/master/index.html#large_enum_variant
-enum-variant-size-threshold = 1032
-# TODO fix, see: https://rust-lang.github.io/rust-clippy/master/index.html#result_large_err
-large-error-threshold = 993
+msrv = "1.85.0"

src/lib.rs

@@ -8,6 +8,9 @@
 #![no_std]
 #![warn(missing_docs)]
 #![allow(clippy::uninlined_format_args)]
+// TODO: these can be removed after <https://github.com/bitcoindevkit/bdk_wallet/issues/245>
+#![allow(clippy::result_large_err)]
+#![allow(clippy::large_enum_variant)]
 
 #[cfg(feature = "std")]
 #[macro_use]

src/persist_test_utils.rs

@@ -164,6 +164,7 @@ where
         local_chain: local_chain_changeset,
         tx_graph: tx_graph_changeset,
         indexer: keychain_txout_changeset,
+        locked_outpoints: Default::default(),
     };
 
     // persist and load
@@ -216,6 +217,7 @@ where
         local_chain: local_chain_changeset,
         tx_graph: tx_graph_changeset,
         indexer: keychain_txout_changeset,
+        locked_outpoints: Default::default(),
     };
 
     // persist, load and check if same as merged

src/wallet/changeset.rs

@@ -1,17 +1,20 @@
 use bdk_chain::{
     indexed_tx_graph, keychain_txout, local_chain, tx_graph, ConfirmationBlockTime, Merge,
 };
+use bitcoin::{OutPoint, Txid};
 use miniscript::{Descriptor, DescriptorPublicKey};
 use serde::{Deserialize, Serialize};
 
 type IndexedTxGraphChangeSet =
     indexed_tx_graph::ChangeSet<ConfirmationBlockTime, keychain_txout::ChangeSet>;
 
-/// A change set for [`Wallet`]
+use crate::locked_outpoints;
+
+/// A change set for [`Wallet`].
 ///
 /// ## Definition
 ///
-/// The change set is responsible for transmiting data between the persistent storage layer and the
+/// The change set is responsible for transmitting data between the persistent storage layer and the
 /// core library components. Specifically, it serves two primary functions:
 ///
 /// 1) Recording incremental changes to the in-memory representation that need to be persisted to
@@ -114,6 +117,8 @@ pub struct ChangeSet {
     pub tx_graph: tx_graph::ChangeSet<ConfirmationBlockTime>,
     /// Changes to [`KeychainTxOutIndex`](keychain_txout::KeychainTxOutIndex).
     pub indexer: keychain_txout::ChangeSet,
+    /// Changes to locked outpoints.
+    pub locked_outpoints: locked_outpoints::ChangeSet,
 }
 
 impl Merge for ChangeSet {
@@ -142,6 +147,9 @@ impl Merge for ChangeSet {
             self.network = other.network;
         }
 
+        // merge locked outpoints
+        self.locked_outpoints.merge(other.locked_outpoints);
+
         Merge::merge(&mut self.local_chain, other.local_chain);
         Merge::merge(&mut self.tx_graph, other.tx_graph);
         Merge::merge(&mut self.indexer, other.indexer);
@@ -154,6 +162,7 @@ impl Merge for ChangeSet {
             && self.local_chain.is_empty()
             && self.tx_graph.is_empty()
             && self.indexer.is_empty()
+            && self.locked_outpoints.is_empty()
     }
 }
 
@@ -163,6 +172,8 @@ impl ChangeSet {
     pub const WALLET_SCHEMA_NAME: &'static str = "bdk_wallet";
     /// Name of table to store wallet descriptors and network.
     pub const WALLET_TABLE_NAME: &'static str = "bdk_wallet";
+    /// Name of table to store wallet locked outpoints.
+    pub const WALLET_OUTPOINT_LOCK_TABLE_NAME: &'static str = "bdk_wallet_locked_outpoints";
 
     /// Get v0 sqlite [ChangeSet] schema
     pub fn schema_v0() -> alloc::string::String {
@@ -177,12 +188,24 @@ impl ChangeSet {
         )
     }
 
+    /// Get v1 sqlite [`ChangeSet`] schema. Schema v1 adds a table for locked outpoints.
+    pub fn schema_v1() -> alloc::string::String {
+        format!(
+            "CREATE TABLE {} ( \
+                txid TEXT NOT NULL, \
+                vout INTEGER NOT NULL, \
+                PRIMARY KEY(txid, vout) \
+                ) STRICT;",
+            Self::WALLET_OUTPOINT_LOCK_TABLE_NAME,
+        )
+    }
+
     /// Initialize sqlite tables for wallet tables.
     pub fn init_sqlite_tables(db_tx: &chain::rusqlite::Transaction) -> chain::rusqlite::Result<()> {
         crate::rusqlite_impl::migrate_schema(
             db_tx,
             Self::WALLET_SCHEMA_NAME,
-            &[&Self::schema_v0()],
+            &[&Self::schema_v0(), &Self::schema_v1()],
         )?;
 
         bdk_chain::local_chain::ChangeSet::init_sqlite_tables(db_tx)?;
@@ -220,6 +243,24 @@ impl ChangeSet {
             changeset.network = network.map(Impl::into_inner);
         }
 
+        // Select locked outpoints.
+        let mut stmt = db_tx.prepare(&format!(
+            "SELECT txid, vout FROM {}",
+            Self::WALLET_OUTPOINT_LOCK_TABLE_NAME,
+        ))?;
+        let rows = stmt.query_map([], |row| {
+            Ok((
+                row.get::<_, Impl<Txid>>("txid")?,
+                row.get::<_, u32>("vout")?,
+            ))
+        })?;
+        let locked_outpoints = &mut changeset.locked_outpoints.outpoints;
+        for row in rows {
+            let (Impl(txid), vout) = row?;
+            let outpoint = OutPoint::new(txid, vout);
+            locked_outpoints.insert(outpoint, true);
+        }
+
         changeset.local_chain = local_chain::ChangeSet::from_sqlite(db_tx)?;
         changeset.tx_graph = tx_graph::ChangeSet::<_>::from_sqlite(db_tx)?;
         changeset.indexer = keychain_txout::ChangeSet::from_sqlite(db_tx)?;
@@ -268,6 +309,30 @@ impl ChangeSet {
             })?;
         }
 
+        // Insert or delete locked outpoints.
+        let mut insert_stmt = db_tx.prepare_cached(&format!(
+            "REPLACE INTO {}(txid, vout) VALUES(:txid, :vout)",
+            Self::WALLET_OUTPOINT_LOCK_TABLE_NAME
+        ))?;
+        let mut delete_stmt = db_tx.prepare_cached(&format!(
+            "DELETE FROM {} WHERE txid=:txid AND vout=:vout",
+            Self::WALLET_OUTPOINT_LOCK_TABLE_NAME,
+        ))?;
+        for (&outpoint, &is_locked) in &self.locked_outpoints.outpoints {
+            let OutPoint { txid, vout } = outpoint;
+            if is_locked {
+                insert_stmt.execute(named_params! {
+                    ":txid": Impl(txid),
+                    ":vout": vout,
+                })?;
+            } else {
+                delete_stmt.execute(named_params! {
+                    ":txid": Impl(txid),
+                    ":vout": vout,
+                })?;
+            }
+        }
+
         self.local_chain.persist_to_sqlite(db_tx)?;
         self.tx_graph.persist_to_sqlite(db_tx)?;
         self.indexer.persist_to_sqlite(db_tx)?;
@@ -311,3 +376,12 @@ impl From<keychain_txout::ChangeSet> for ChangeSet {
         }
     }
 }
+
+impl From<locked_outpoints::ChangeSet> for ChangeSet {
+    fn from(locked_outpoints: locked_outpoints::ChangeSet) -> Self {
+        Self {
+            locked_outpoints,
+            ..Default::default()
+        }
+    }
+}

src/wallet/locked_outpoints.rs

@@ -0,0 +1,26 @@
+//! Module containing the locked outpoints change set.
+
+use bdk_chain::Merge;
+use bitcoin::OutPoint;
+use serde::{Deserialize, Serialize};
+
+use crate::collections::BTreeMap;
+
+/// Represents changes to locked outpoints.
+#[derive(Debug, Clone, Default, PartialEq, Serialize, Deserialize)]
+pub struct ChangeSet {
+    /// The lock status of an outpoint, `true == is_locked`.
+    pub outpoints: BTreeMap<OutPoint, bool>,
+}
+
+impl Merge for ChangeSet {
+    fn merge(&mut self, other: Self) {
+        // Extend self with other. Any entries in `self` that share the same
+        // outpoint are overwritten.
+        self.outpoints.extend(other.outpoints);
+    }
+
+    fn is_empty(&self) -> bool {
+        self.outpoints.is_empty()
+    }
+}

src/wallet/mod.rs

@@ -53,6 +53,7 @@ mod changeset;
 pub mod coin_selection;
 pub mod error;
 pub mod export;
+pub mod locked_outpoints;
 mod params;
 mod persisted;
 pub mod signer;
@@ -109,6 +110,7 @@ pub struct Wallet {
     stage: ChangeSet,
     network: Network,
     secp: SecpCtx,
+    locked_outpoints: HashSet<OutPoint>,
 }
 
 /// An update to [`Wallet`].
@@ -473,6 +475,8 @@ impl Wallet {
             None => (None, Arc::new(SignersContainer::new())),
         };
 
+        let locked_outpoints = HashSet::new();
+
         let mut stage = ChangeSet {
             descriptor: Some(descriptor.clone()),
             change_descriptor: change_descriptor.clone(),
@@ -499,6 +503,7 @@ impl Wallet {
             indexed_graph,
             stage,
             secp,
+            locked_outpoints,
         })
     }
 
@@ -674,6 +679,14 @@ impl Wallet {
             None => Arc::new(SignersContainer::new()),
         };
 
+        // Apply locked outpoints
+        let locked_outpoints = changeset.locked_outpoints.outpoints;
+        let locked_outpoints = locked_outpoints
+            .into_iter()
+            .filter(|&(_op, is_locked)| is_locked)
+            .map(|(op, _)| op)
+            .collect();
+
         let mut stage = ChangeSet::default();
 
         let indexed_graph = make_indexed_graph(
@@ -695,6 +708,7 @@ impl Wallet {
             stage,
             network,
             secp,
+            locked_outpoints,
         }))
     }
 
@@ -2140,6 +2154,8 @@ impl Wallet {
                     CanonicalizationParams::default(),
                     self.indexed_graph.index.outpoints().iter().cloned(),
                 )
+                // Filter out locked outpoints
+                .filter(|(_, txo)| !self.is_outpoint_locked(txo.outpoint))
                 // only create LocalOutput if UTxO is mature
                 .filter_map(move |((k, i), full_txo)| {
                     full_txo
@@ -2408,6 +2424,51 @@ impl Wallet {
         &self.chain
     }
 
+    /// List the locked outpoints.
+    pub fn list_locked_outpoints(&self) -> impl Iterator<Item = OutPoint> + '_ {
+        self.locked_outpoints.iter().copied()
+    }
+
+    /// List unspent outpoints that are currently locked.
+    pub fn list_locked_unspent(&self) -> impl Iterator<Item = OutPoint> + '_ {
+        self.list_unspent()
+            .filter(|output| self.is_outpoint_locked(output.outpoint))
+            .map(|output| output.outpoint)
+    }
+
+    /// Whether the `outpoint` is locked. See [`Wallet::lock_outpoint`] for more.
+    pub fn is_outpoint_locked(&self, outpoint: OutPoint) -> bool {
+        self.locked_outpoints.contains(&outpoint)
+    }
+
+    /// Lock a wallet output identified by the given `outpoint`.
+    ///
+    /// A locked UTXO will not be selected as an input to fund a transaction. This is useful
+    /// for excluding or reserving candidate inputs during transaction creation.
+    ///
+    /// **You must persist the staged change for the lock status to be persistent**. To unlock a
+    /// previously locked outpoint, see [`Wallet::unlock_outpoint`].
+    pub fn lock_outpoint(&mut self, outpoint: OutPoint) {
+        if self.locked_outpoints.insert(outpoint) {
+            let changeset = locked_outpoints::ChangeSet {
+                outpoints: [(outpoint, true)].into(),
+            };
+            self.stage.merge(changeset.into());
+        }
+    }
+
+    /// Unlock the wallet output of the specified `outpoint`.
+    ///
+    /// **You must persist the staged change for the lock status to be persistent**.
+    pub fn unlock_outpoint(&mut self, outpoint: OutPoint) {
+        if self.locked_outpoints.remove(&outpoint) {
+            let changeset = locked_outpoints::ChangeSet {
+                outpoints: [(outpoint, false)].into(),
+            };
+            self.stage.merge(changeset.into());
+        }
+    }
+
     /// Introduces a `block` of `height` to the wallet, and tries to connect it to the
     /// `prev_blockhash` of the block's header.
     ///