sweep: make sure exclusive inputs are not grouped

This commit fixes the grouping logic in `BudgetAggregator` to make sure
the exclusive inputs are never grouped.

sweep/aggregator.go

@@ -496,10 +496,12 @@ type clusterGroup map[fn.Option[int32]][]SweeperInput
 
 // ClusterInputs creates a list of input sets from pending inputs.
 // 1. filter out inputs whose budget cannot cover min relay fee.
-// 2. group the inputs into clusters based on their deadline height.
-// 3. sort the inputs in each cluster by their budget.
-// 4. optionally split a cluster if it exceeds the max input limit.
-// 5. create input sets from each of the clusters.
+// 2. filter a list of exclusive inputs.
+// 3. group the inputs into clusters based on their deadline height.
+// 4. sort the inputs in each cluster by their budget.
+// 5. optionally split a cluster if it exceeds the max input limit.
+// 6. create input sets from each of the clusters.
+// 7. create input sets for each of the exclusive inputs.
 func (b *BudgetAggregator) ClusterInputs(inputs InputsMap) []InputSet {
 	// Filter out inputs that have a budget below min relay fee.
 	filteredInputs := b.filterInputs(inputs)
@@ -507,9 +509,22 @@ func (b *BudgetAggregator) ClusterInputs(inputs InputsMap) []InputSet {
 	// Create clusters to group inputs based on their deadline height.
 	clusters := make(clusterGroup, len(filteredInputs))
 
+	// exclusiveInputs is a set of inputs that are not to be included in
+	// any cluster. These inputs can only be swept independently as there's
+	// no guarantee which input will be confirmed first, which means
+	// grouping exclusive inputs may jeopardize non-exclusive inputs.
+	exclusiveInputs := make(InputsMap)
+
 	// Iterate all the inputs and group them based on their specified
 	// deadline heights.
 	for _, input := range filteredInputs {
+		// Put exclusive inputs in their own set.
+		if input.params.ExclusiveGroup != nil {
+			log.Tracef("Input %v is exclusive", input.OutPoint())
+			exclusiveInputs[*input.OutPoint()] = input
+			continue
+		}
+
 		height := input.params.DeadlineHeight
 		cluster, ok := clusters[height]
 		if !ok {
@@ -534,6 +549,12 @@ func (b *BudgetAggregator) ClusterInputs(inputs InputsMap) []InputSet {
 		inputSets = append(inputSets, sets...)
 	}
 
+	// Create input sets from the exclusive inputs.
+	for _, input := range exclusiveInputs {
+		sets := b.createInputSets([]SweeperInput{*input})
+		inputSets = append(inputSets, sets...)
+	}
+
 	return inputSets
 }
 

sweep/aggregator_test.go

@@ -801,10 +801,10 @@ func TestBudgetInputSetClusterInputs(t *testing.T) {
 	wt := &input.MockWitnessType{}
 	defer wt.AssertExpectations(t)
 
-	// Mock the `SizeUpperBound` method to return the size six times since
-	// we are using nine inputs.
+	// Mock the `SizeUpperBound` method to return the size 10 times since
+	// we are using ten inputs.
 	const wtSize = 100
-	wt.On("SizeUpperBound").Return(wtSize, true, nil).Times(9)
+	wt.On("SizeUpperBound").Return(wtSize, true, nil).Times(10)
 	wt.On("String").Return("mock witness type")
 
 	// Mock the estimator to return a constant fee rate.
@@ -827,6 +827,36 @@ func TestBudgetInputSetClusterInputs(t *testing.T) {
 	// Create testing pending inputs.
 	inputs := make(InputsMap)
 
+	// Create a mock input that is exclusive.
+	inpExclusive := &input.MockInput{}
+	defer inpExclusive.AssertExpectations(t)
+
+	// We expect the high budget input to call this method three times,
+	// 1. in `filterInputs`
+	// 2. in `createInputSet`
+	// 3. when assigning the input to the exclusiveInputs.
+	// 4. when iterating the exclusiveInputs.
+	opExclusive := wire.OutPoint{Hash: chainhash.Hash{1, 2, 3, 4, 5}}
+	inpExclusive.On("OutPoint").Return(&opExclusive).Times(4)
+
+	// Mock the `WitnessType` method to return the witness type.
+	inpExclusive.On("WitnessType").Return(wt)
+
+	// Mock the `RequiredTxOut` to return nil.
+	inpExclusive.On("RequiredTxOut").Return(nil)
+
+	// Add the exclusive input to the inputs map. We expect this input to
+	// be in its own input set although it has deadline1.
+	exclusiveGroup := uint64(123)
+	inputs[opExclusive] = &SweeperInput{
+		Input: inpExclusive,
+		params: Params{
+			Budget:         budgetHigh,
+			DeadlineHeight: deadline1,
+			ExclusiveGroup: &exclusiveGroup,
+		},
+	}
+
 	// For each deadline height, create two inputs with different budgets,
 	// one below the min fee rate and one above it. We should see the lower
 	// one being filtered out.
@@ -910,12 +940,17 @@ func TestBudgetInputSetClusterInputs(t *testing.T) {
 	// Call the method under test.
 	result := b.ClusterInputs(inputs)
 
-	// We expect three input sets to be returned, one for each deadline.
-	require.Len(t, result, 3)
+	// We expect four input sets to be returned, one for each deadline and
+	// extra one for the exclusive input.
+	require.Len(t, result, 4)
 
-	// Check each input set has exactly two inputs.
+	// The last set should be the exclusive input that has only one input.
+	setExclusive := result[3]
+	require.Len(t, setExclusive.Inputs(), 1)
+
+	// Check the each of rest has exactly two inputs.
 	deadlines := make(map[fn.Option[int32]]struct{})
-	for _, set := range result {
+	for _, set := range result[:3] {
 		// We expect two inputs in each set.
 		require.Len(t, set.Inputs(), 2)