staticaddr/deposit: async finalization cleanup

FinalizeDepositAction only needs to tell the manager to remove the FSM from its
active set, but the old synchronous send was still tied to the caller context
and could race with request cancellation or a busy manager loop.

Send the cleanup notification asynchronously and tie it to the FSM lifetime
instead. Withdrawal completion no longer blocks while deposit locks are held
just because the original request context was canceled.

staticaddr/deposit/actions.go

@@ -161,14 +161,25 @@ func (f *FSM) WaitForExpirySweepAction(ctx context.Context,
 
 // FinalizeDepositAction is the final action after a withdrawal. It signals to
 // the manager that the deposit has been swept and the FSM can be removed.
-func (f *FSM) FinalizeDepositAction(ctx context.Context,
+func (f *FSM) FinalizeDepositAction(_ context.Context,
 	_ fsm.EventContext) fsm.EventType {
 
-	select {
-	case <-ctx.Done():
-		return fsm.OnError
+	outpoint := f.deposit.OutPoint
 
-	case f.finalizedDepositChan <- f.deposit.OutPoint:
-		return fsm.NoOp
-	}
+	// The finalization notification only tells the manager to remove the
+	// deposit from its active set. Send it asynchronously so a busy manager
+	// loop can't stall withdrawal confirmation while deposit locks are held.
+	go func() {
+		select {
+		case <-f.quitChan:
+			// The deposit is already in a final state. If shutdown wins
+			// this race, startup recovery will skip it instead of
+			// re-adding it to the active set.
+			return
+
+		case f.finalizedDepositChan <- outpoint:
+		}
+	}()
+
+	return fsm.NoOp
 }

staticaddr/deposit/actions_test.go

@@ -0,0 +1,135 @@
+package deposit
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/btcsuite/btcd/chaincfg/chainhash"
+	"github.com/btcsuite/btcd/wire"
+	"github.com/lightninglabs/loop/fsm"
+	"github.com/stretchr/testify/require"
+)
+
+// TestFinalizeDepositActionDoesNotBlock ensures the final cleanup notification
+// does not block the withdrawal completion path while the manager loop is busy.
+func TestFinalizeDepositActionDoesNotBlock(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	outpoint := wire.OutPoint{
+		Hash:  chainhash.Hash{1},
+		Index: 1,
+	}
+
+	depositFSM := &FSM{
+		deposit: &Deposit{
+			OutPoint: outpoint,
+		},
+		quitChan:             make(chan struct{}),
+		finalizedDepositChan: make(chan wire.OutPoint),
+	}
+
+	resultChan := make(chan fsm.EventType, 1)
+	go func() {
+		resultChan <- depositFSM.FinalizeDepositAction(ctx, nil)
+	}()
+
+	select {
+	case result := <-resultChan:
+		require.Equal(t, fsm.NoOp, result)
+
+	case <-time.After(100 * time.Millisecond):
+		t.Fatal("FinalizeDepositAction blocked on manager cleanup")
+	}
+
+	select {
+	case gotOutpoint := <-depositFSM.finalizedDepositChan:
+		require.Equal(t, outpoint, gotOutpoint)
+
+	case <-time.After(time.Second):
+		t.Fatal("finalization cleanup notification was not delivered")
+	}
+}
+
+// TestFinalizeDepositActionIgnoresRequestCancellation ensures the cleanup
+// notification is tied to the FSM lifetime, not the caller's request context.
+func TestFinalizeDepositActionIgnoresRequestCancellation(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	quitChan := make(chan struct{})
+	defer close(quitChan)
+
+	outpoint := wire.OutPoint{
+		Hash:  chainhash.Hash{2},
+		Index: 2,
+	}
+
+	depositFSM := &FSM{
+		deposit: &Deposit{
+			OutPoint: outpoint,
+		},
+		quitChan:             quitChan,
+		finalizedDepositChan: make(chan wire.OutPoint),
+	}
+
+	resultChan := make(chan fsm.EventType, 1)
+	go func() {
+		resultChan <- depositFSM.FinalizeDepositAction(ctx, nil)
+	}()
+
+	select {
+	case result := <-resultChan:
+		require.Equal(t, fsm.NoOp, result)
+
+	case <-time.After(100 * time.Millisecond):
+		t.Fatal("FinalizeDepositAction blocked on manager cleanup")
+	}
+
+	cancel()
+
+	select {
+	case gotOutpoint := <-depositFSM.finalizedDepositChan:
+		require.Equal(t, outpoint, gotOutpoint)
+
+	case <-time.After(time.Second):
+		t.Fatal("finalization cleanup notification was dropped after " +
+			"request cancellation")
+	}
+}
+
+// TestFinalizeDepositActionIgnoresCanceledContext ensures the final cleanup
+// notification is still queued even if the caller's context is already done.
+func TestFinalizeDepositActionIgnoresCanceledContext(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	quitChan := make(chan struct{})
+	defer close(quitChan)
+
+	outpoint := wire.OutPoint{
+		Hash:  chainhash.Hash{3},
+		Index: 3,
+	}
+
+	depositFSM := &FSM{
+		deposit: &Deposit{
+			OutPoint: outpoint,
+		},
+		quitChan:             quitChan,
+		finalizedDepositChan: make(chan wire.OutPoint),
+	}
+
+	result := depositFSM.FinalizeDepositAction(ctx, nil)
+	require.Equal(t, fsm.NoOp, result)
+
+	select {
+	case gotOutpoint := <-depositFSM.finalizedDepositChan:
+		require.Equal(t, outpoint, gotOutpoint)
+
+	case <-time.After(time.Second):
+		t.Fatal("finalization cleanup notification was dropped for " +
+			"an already-canceled request context")
+	}
+}