sweep: roll back wallet inputs on all AddWalletInputs error paths

docs/release-notes/release-notes-0.21.0.md

@@ -71,7 +71,7 @@
   the chain watch filter on restart. This was a pre-existing bug since
   private taproot channels were first introduced.
 
-* [Fixed a shutdown race in the 
+* [Fixed a shutdown race in the
   channel link](https://github.com/lightningnetwork/lnd/pull/10719)
   that could deadlock the invoice registry during concurrent peer disconnect.
   The link now waits for `htlcManager` to fully exit before tearing down hodl
@@ -88,6 +88,13 @@
   RBF close state machine does not yet thread through the `AuxCloser` hook
   that overlay channels rely on to build aux-aware close transactions.
 
+- [Fixed `BudgetInputSet.AddWalletInputs` to roll back partially-added
+  wallet inputs on error](https://github.com/lightningnetwork/lnd/pull/10723).
+  Previously, if adding a wallet input failed midway through the loop, any
+  inputs already appended to the set would remain, leaving it in an
+  inconsistent state. The method now restores the input set to its original
+  state before returning the error.
+
 # New Features
 
 - [Basic Support](https://github.com/lightningnetwork/lnd/pull/9868) for onion

sweep/tx_input_set.go

@@ -367,10 +367,16 @@ func (b *BudgetInputSet) AddWalletInputs(wallet Wallet) error {
 		return utxos[i].Value < utxos[j].Value
 	})
 
+	// We'll track the initial number of inputs to ensure we can restore the
+	// set to its original state if we fail to add the required wallet
+	// inputs.
+	inputsBefore := len(b.inputs)
+
 	// Add wallet inputs to the set until the specified budget is covered.
 	for _, utxo := range utxos {
 		err := b.addWalletInput(utxo)
 		if err != nil {
+			b.inputs = b.inputs[:inputsBefore]
 			return err
 		}