Fuzzer for Pallet Bags List (#9851)

* Fuzzer for Pallet Bags List

* Some small updates

* Fuzzer for Pallet Bags List

This PR adds a fuzzer for the `SortedListProvider` API exposed by pallet-bags-list.

* Feature gate code NOT used by fuzz feature

* Create Enum for list actions

* fix some small mistakes

* try and make CI happy

* fmt

* Do not insert before updating

* clean up some misc. comments

* marginally improve Node::sanity_check

* Change ID_RANGE to 25_000

* comma

* try improve correct feature gating so no unused code

Co-authored-by: thiolliere <gui.thiolliere@gmail.com>

substrate/frame/bags-list/src/lib.rs

@@ -59,8 +59,8 @@ use sp_std::prelude::*;
 mod benchmarks;
 
 mod list;
-#[cfg(test)]
-mod mock;
+#[cfg(any(test, feature = "fuzz"))]
+pub mod mock;
 #[cfg(test)]
 mod tests;
 pub mod weights;

substrate/frame/bags-list/src/list/mod.rs

@@ -391,8 +391,8 @@ impl<T: Config> List<T> {
 	///
 	/// * there are no duplicate ids,
 	/// * length of this list is in sync with `CounterForListNodes`,
-	/// * and sanity-checks all bags. This will cascade down all the checks and makes sure all bags
-	///   are checked per *any* update to `List`.
+	/// * and sanity-checks all bags and nodes. This will cascade down all the checks and makes sure
+	/// all bags and nodes are checked per *any* update to `List`.
 	#[cfg(feature = "std")]
 	pub(crate) fn sanity_check() -> Result<(), &'static str> {
 		use frame_support::ensure;
@@ -414,7 +414,6 @@ impl<T: Config> List<T> {
 			let thresholds = T::BagThresholds::get().iter().copied();
 			let thresholds: Vec<u64> = if thresholds.clone().last() == Some(VoteWeight::MAX) {
 				// in the event that they included it, we don't need to make any changes
-				// Box::new(thresholds.collect()
 				thresholds.collect()
 			} else {
 				// otherwise, insert it here.
@@ -774,10 +773,13 @@ impl<T: Config> Node<T> {
 			"node does not exist in the expected bag"
 		);
 
+		let non_terminal_check = !self.is_terminal() &&
+			expected_bag.head.as_ref() != Some(id) &&
+			expected_bag.tail.as_ref() != Some(id);
+		let terminal_check =
+			expected_bag.head.as_ref() == Some(id) || expected_bag.tail.as_ref() == Some(id);
 		frame_support::ensure!(
-			!self.is_terminal() ||
-				expected_bag.head.as_ref() == Some(id) ||
-				expected_bag.tail.as_ref() == Some(id),
+			non_terminal_check || terminal_check,
 			"a terminal node is neither its bag head or tail"
 		);
 

substrate/frame/bags-list/src/mock.rs

@@ -101,12 +101,13 @@ pub(crate) const GENESIS_IDS: [(AccountId, VoteWeight); 4] =
 	[(1, 10), (2, 1_000), (3, 1_000), (4, 1_000)];
 
 #[derive(Default)]
-pub(crate) struct ExtBuilder {
+pub struct ExtBuilder {
 	ids: Vec<(AccountId, VoteWeight)>,
 }
 
 impl ExtBuilder {
 	/// Add some AccountIds to insert into `List`.
+	#[cfg(test)]
 	pub(crate) fn add_ids(mut self, ids: Vec<(AccountId, VoteWeight)>) -> Self {
 		self.ids = ids;
 		self
@@ -126,18 +127,20 @@ impl ExtBuilder {
 		ext
 	}
 
-	pub(crate) fn build_and_execute(self, test: impl FnOnce() -> ()) {
+	pub fn build_and_execute(self, test: impl FnOnce() -> ()) {
 		self.build().execute_with(|| {
 			test();
 			List::<Runtime>::sanity_check().expect("Sanity check post condition failed")
 		})
 	}
 
+	#[cfg(test)]
 	pub(crate) fn build_and_execute_no_post_check(self, test: impl FnOnce() -> ()) {
 		self.build().execute_with(test)
 	}
 }
 
+#[cfg(test)]
 pub(crate) mod test_utils {
 	use super::*;
 	use list::Bag;