Drop Deref indirection for OutputSpender

LDK

Lightning Dev Kit/rust-lightning

644ca0c6 View source ↗

Public commit record

What the developer wrote

Authored by Valentine Wallace

68/100 · Adequate

Drop Deref indirection for OutputSpender

Reduces generics and verbosity across the codebase, should provide equivalent
behavior.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

✓ Descriptive subject✓ Names a concrete action or component✓ Provides detailed explanatory context

The short version

What changed, and why it matters

This is a routine Rust code cleanup change. It removes the requirement that an OutputSpender must be wrapped in a Deref pointer (like Arc or reference), and instead makes OutputSpender work directly through a blanket implementation. The commit message says it reduces generics and verbosity while keeping the same behavior. There is no security fix here.

Recommended action

No security action needed. Treat as normal code maintenance.

Security signals we found

No strong security signals were identified.

Technical analysis

Evidence from the diff

The patch refactors trait bounds from O: Deref where O::Target: OutputSpender to O: OutputSpender across background processor, signer, and sweeper modules. A blanket impl impl<T: OutputSpender + ?Sized, O: Deref<Target = T>> OutputSpender for O is added so that smart pointers/references to OutputSpender still implement OutputSpender. This is a pure ergonomics/refactoring change with no functional or security behavior change.

Changed components

lightning-background-processor/src/lib.rslightning/src/sign/mod.rslightning/src/util/sweep.rs

Inspect captured patch +30 / −26

diff --git a/lightning-background-processor/src/lib.rs b/lightning-background-processor/src/lib.rs
index 905782c..d765cca 100644
--- a/lightning-background-processor/src/lib.rs
+++ b/lightning-background-processor/src/lib.rs
@@ -946,7 +946,7 @@ pub async fn process_events_async<
 	PM: Deref,
 	LM: Deref,
 	D: Deref,
-	O: Deref,
+	O: OutputSpender,
 	K: KVStore,
 	OS: Deref<Target = OutputSweeper<T, D, F, CF, K, L, O>>,
 	S: Deref<Target = SC>,
@@ -967,7 +967,6 @@ where
 	OM::Target: AOnionMessenger,
 	PM::Target: APeerManager,
 	LM::Target: ALiquidityManager,
-	O::Target: OutputSpender,
 	D::Target: ChangeDestinationSource,
 {
 	let async_event_handler = |event| {
@@ -1441,7 +1440,7 @@ pub async fn process_events_async_with_kv_store_sync<
 	PM: Deref,
 	LM: Deref,
 	D: Deref,
-	O: Deref,
+	O: OutputSpender,
 	K: Deref,
 	OS: Deref<Target = OutputSweeperSync<T, D, F, CF, K, L, O>>,
 	S: Deref<Target = SC>,
@@ -1462,7 +1461,6 @@ where
 	OM::Target: AOnionMessenger,
 	PM::Target: APeerManager,
 	LM::Target: ALiquidityManager,
-	O::Target: OutputSpender,
 	D::Target: ChangeDestinationSourceSync,
 	K::Target: KVStoreSync,
 {
@@ -1556,7 +1554,7 @@ impl BackgroundProcessor {
 		S: 'static + Deref<Target = SC> + Send + Sync,
 		SC: for<'b> WriteableScore<'b>,
 		D: 'static + Deref,
-		O: 'static + Deref,
+		O: 'static + OutputSpender,
 		K: 'static + Deref + Send,
 		OS: 'static + Deref<Target = OutputSweeperSync<T, D, F, CF, K, L, O>> + Send,
 	>(
@@ -1573,7 +1571,6 @@ impl BackgroundProcessor {
 		PM::Target: APeerManager,
 		LM::Target: ALiquidityManagerSync,
 		D::Target: ChangeDestinationSourceSync,
-		O::Target: 'static + OutputSpender,
 		K::Target: 'static + KVStoreSync,
 	{
 		let stop_thread = Arc::new(AtomicBool::new(false));
diff --git a/lightning/src/sign/mod.rs b/lightning/src/sign/mod.rs
index f4f4c5c..84bfbb9 100644
--- a/lightning/src/sign/mod.rs
+++ b/lightning/src/sign/mod.rs
@@ -1063,6 +1063,23 @@ pub trait OutputSpender {
 	) -> Result<Transaction, ()>;
 }
 
+impl<T: OutputSpender + ?Sized, O: Deref<Target = T>> OutputSpender for O {
+	fn spend_spendable_outputs(
+		&self, descriptors: &[&SpendableOutputDescriptor], outputs: Vec<TxOut>,
+		change_destination_script: ScriptBuf, feerate_sat_per_1000_weight: u32,
+		locktime: Option<LockTime>, secp_ctx: &Secp256k1<All>,
+	) -> Result<Transaction, ()> {
+		self.deref().spend_spendable_outputs(
+			descriptors,
+			outputs,
+			change_destination_script,
+			feerate_sat_per_1000_weight,
+			locktime,
+			secp_ctx,
+		)
+	}
+}
+
 // Primarily needed in doctests because of https://github.com/rust-lang/rust/issues/67295
 /// A dynamic [`SignerProvider`] temporarily needed for doc tests.
 ///
diff --git a/lightning/src/util/sweep.rs b/lightning/src/util/sweep.rs
index e69b3a9..2aef218 100644
--- a/lightning/src/util/sweep.rs
+++ b/lightning/src/util/sweep.rs
@@ -344,10 +344,9 @@ pub struct OutputSweeper<
 	F: Filter,
 	K: KVStore,
 	L: Logger,
-	O: Deref,
+	O: OutputSpender,
 > where
 	D::Target: ChangeDestinationSource,
-	O::Target: OutputSpender,
 {
 	sweeper_state: Mutex<SweeperState>,
 	pending_sweep: AtomicBool,
@@ -367,11 +366,10 @@ impl<
 		F: Filter,
 		K: KVStore,
 		L: Logger,
-		O: Deref,
+		O: OutputSpender,
 	> OutputSweeper<B, D, E, F, K, L, O>
 where
 	D::Target: ChangeDestinationSource,
-	O::Target: OutputSpender,
 {
 	/// Constructs a new [`OutputSweeper`].
 	///
@@ -721,11 +719,10 @@ impl<
 		F: Filter + Sync + Send,
 		K: KVStore,
 		L: Logger,
-		O: Deref,
+		O: OutputSpender,
 	> Listen for OutputSweeper<B, D, E, F, K, L, O>
 where
 	D::Target: ChangeDestinationSource,
-	O::Target: OutputSpender,
 {
 	fn filtered_block_connected(
 		&self, header: &Header, txdata: &chain::transaction::TransactionData, height: u32,
@@ -764,11 +761,10 @@ impl<
 		F: Filter + Sync + Send,
 		K: KVStore,
 		L: Logger,
-		O: Deref,
+		O: OutputSpender,
 	> Confirm for OutputSweeper<B, D, E, F, K, L, O>
 where
 	D::Target: ChangeDestinationSource,
-	O::Target: OutputSpender,
 {
 	fn transactions_confirmed(
 		&self, header: &Header, txdata: &chain::transaction::TransactionData, height: u32,
@@ -863,11 +859,10 @@ impl<
 		F: Filter + Sync + Send,
 		K: KVStore,
 		L: Logger,
-		O: Deref,
+		O: OutputSpender,
 	> ReadableArgs<(B, E, Option<F>, O, D, K, L)> for (BestBlock, OutputSweeper<B, D, E, F, K, L, O>)
 where
 	D::Target: ChangeDestinationSource,
-	O::Target: OutputSpender,
 {
 	#[inline]
 	fn read<R: io::Read>(
@@ -935,11 +930,10 @@ pub struct OutputSweeperSync<
 	F: Filter,
 	K: Deref,
 	L: Logger,
-	O: Deref,
+	O: OutputSpender,
 > where
 	D::Target: ChangeDestinationSourceSync,
 	K::Target: KVStoreSync,
-	O::Target: OutputSpender,
 {
 	sweeper:
 		OutputSweeper<B, ChangeDestinationSourceSyncWrapper<D>, E, F, KVStoreSyncWrapper<K>, L, O>,
@@ -952,12 +946,11 @@ impl<
 		F: Filter,
 		K: Deref,
 		L: Logger,
-		O: Deref,
+		O: OutputSpender,
 	> OutputSweeperSync<B, D, E, F, K, L, O>
 where
 	D::Target: ChangeDestinationSourceSync,
 	K::Target: KVStoreSync,
-	O::Target: OutputSpender,
 {
 	/// Constructs a new [`OutputSweeperSync`] instance.
 	///
@@ -1075,12 +1068,11 @@ impl<
 		F: Filter + Sync + Send,
 		K: Deref,
 		L: Logger,
-		O: Deref,
+		O: OutputSpender,
 	> Listen for OutputSweeperSync<B, D, E, F, K, L, O>
 where
 	D::Target: ChangeDestinationSourceSync,
 	K::Target: KVStoreSync,
-	O::Target: OutputSpender,
 {
 	fn filtered_block_connected(
 		&self, header: &Header, txdata: &chain::transaction::TransactionData, height: u32,
@@ -1100,12 +1092,11 @@ impl<
 		F: Filter + Sync + Send,
 		K: Deref,
 		L: Logger,
-		O: Deref,
+		O: OutputSpender,
 	> Confirm for OutputSweeperSync<B, D, E, F, K, L, O>
 where
 	D::Target: ChangeDestinationSourceSync,
 	K::Target: KVStoreSync,
-	O::Target: OutputSpender,
 {
 	fn transactions_confirmed(
 		&self, header: &Header, txdata: &chain::transaction::TransactionData, height: u32,
@@ -1133,13 +1124,12 @@ impl<
 		F: Filter + Sync + Send,
 		K: Deref,
 		L: Logger,
-		O: Deref,
+		O: OutputSpender,
 	> ReadableArgs<(B, E, Option<F>, O, D, K, L)>
 	for (BestBlock, OutputSweeperSync<B, D, E, F, K, L, O>)
 where
 	D::Target: ChangeDestinationSourceSync,
 	K::Target: KVStoreSync,
-	O::Target: OutputSpender,
 {
 	#[inline]
 	fn read<R: io::Read>(

Risk score

Why this scored 15/100

Our methodology →

Potential impact 0/30

Exploitability 0/25

Stealth signal 0/15

Affected reach 0/15

Confidence 10/10

Evidence quality 5/5

Human-validated context

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What the developer wrote

What changed, and why it matters

Security signals we found

Evidence from the diff

Changed components

Why this scored 15/100

Community notes

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