Merge pull request lightningdevkit#4033 from benthecarman/randomize-sweeper

Randomize order of inputs from `OutputSweeper`

Author: tnull

lightning/src/util/sweep.rs

@@ -574,13 +574,19 @@ where
 				let cur_height = sweeper_state.best_block.height;
 				let cur_hash = sweeper_state.best_block.block_hash;
 
-				let respend_descriptors: Vec<&SpendableOutputDescriptor> = sweeper_state
+				let respend_descriptors_set: HashSet<&SpendableOutputDescriptor> = sweeper_state
 					.outputs
 					.iter()
 					.filter(|o| filter_fn(*o, cur_height))
 					.map(|o| &o.descriptor)
 					.collect();
 
+				// we first collect into a set to avoid duplicates and to "randomize" the order
+				// in which outputs are spent. Then we collect into a vec as that is what
+				// `spend_outputs` requires.
+				let respend_descriptors: Vec<&SpendableOutputDescriptor> =
+					respend_descriptors_set.into_iter().collect();
+
 				// Generate the spending transaction and broadcast it.
 				if !respend_descriptors.is_empty() {
 					let spending_tx = self