From 019d4e3b995cca8ac45b2e7954008d6278e27ffe Mon Sep 17 00:00:00 2001
From: Andronik Ordian <write@reusable.software>
Date: Wed, 29 Sep 2021 20:58:04 +0200
Subject: [PATCH] paras_inherent: reject only candidates with concluded
 disputes (#3969)

* paras_inherent: reject only candidates with concluded disputes

* remove unused Error variant
---
 polkadot/runtime/parachains/src/disputes.rs   | 23 +++++++++----------
 .../runtime/parachains/src/paras_inherent.rs  | 10 ++++----
 2 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/polkadot/runtime/parachains/src/disputes.rs b/polkadot/runtime/parachains/src/disputes.rs
index aa7acee6d2..b63305efb2 100644
--- a/polkadot/runtime/parachains/src/disputes.rs
+++ b/polkadot/runtime/parachains/src/disputes.rs
@@ -129,9 +129,8 @@ pub trait DisputesHandler<BlockNumber> {
 		included_in: BlockNumber,
 	);
 
-	/// Whether the given candidate could be invalid, i.e. there is an ongoing
-	/// or concluded dispute with supermajority-against.
-	fn could_be_invalid(session: SessionIndex, candidate_hash: CandidateHash) -> bool;
+	/// Whether the given candidate concluded invalid in a dispute with supermajority.
+	fn concluded_invalid(session: SessionIndex, candidate_hash: CandidateHash) -> bool;
 
 	/// Called by the initializer to initialize the configuration module.
 	fn initializer_initialize(now: BlockNumber) -> Weight;
@@ -165,7 +164,7 @@ impl<BlockNumber> DisputesHandler<BlockNumber> for () {
 	) {
 	}
 
-	fn could_be_invalid(_session: SessionIndex, _candidate_hash: CandidateHash) -> bool {
+	fn concluded_invalid(_session: SessionIndex, _candidate_hash: CandidateHash) -> bool {
 		false
 	}
 
@@ -201,8 +200,8 @@ impl<T: Config> DisputesHandler<T::BlockNumber> for pallet::Pallet<T> {
 		pallet::Pallet::<T>::note_included(session, candidate_hash, included_in)
 	}
 
-	fn could_be_invalid(session: SessionIndex, candidate_hash: CandidateHash) -> bool {
-		pallet::Pallet::<T>::could_be_invalid(session, candidate_hash)
+	fn concluded_invalid(session: SessionIndex, candidate_hash: CandidateHash) -> bool {
+		pallet::Pallet::<T>::concluded_invalid(session, candidate_hash)
 	}
 
 	fn initializer_initialize(now: T::BlockNumber) -> Weight {
@@ -1114,10 +1113,10 @@ impl<T: Config> Pallet<T> {
 		}
 	}
 
-	pub(crate) fn could_be_invalid(session: SessionIndex, candidate_hash: CandidateHash) -> bool {
+	pub(crate) fn concluded_invalid(session: SessionIndex, candidate_hash: CandidateHash) -> bool {
 		<Disputes<T>>::get(&session, &candidate_hash).map_or(false, |dispute| {
-			// A dispute that is ongoing or has concluded with supermajority-against.
-			dispute.concluded_at.is_none() || has_supermajority_against(&dispute)
+			// A dispute that has concluded with supermajority-against.
+			has_supermajority_against(&dispute)
 		})
 	}
 
@@ -2207,9 +2206,9 @@ mod tests {
 				]
 			);
 
-			assert_eq!(Pallet::<Test>::could_be_invalid(3, candidate_hash.clone()), false); // It has 5 votes for
-			assert_eq!(Pallet::<Test>::could_be_invalid(4, candidate_hash.clone()), true);
-			assert_eq!(Pallet::<Test>::could_be_invalid(5, candidate_hash.clone()), true);
+			assert!(!Pallet::<Test>::concluded_invalid(3, candidate_hash.clone()));
+			assert!(!Pallet::<Test>::concluded_invalid(4, candidate_hash.clone()));
+			assert!(Pallet::<Test>::concluded_invalid(5, candidate_hash.clone()));
 
 			// Ensure inclusion removes spam slots
 			assert_eq!(SpamSlots::<Test>::get(4), Some(vec![0, 0, 1, 1, 0, 0, 0]));
diff --git a/polkadot/runtime/parachains/src/paras_inherent.rs b/polkadot/runtime/parachains/src/paras_inherent.rs
index a972dbfaa3..9ac8e01415 100644
--- a/polkadot/runtime/parachains/src/paras_inherent.rs
+++ b/polkadot/runtime/parachains/src/paras_inherent.rs
@@ -66,8 +66,8 @@ pub mod pallet {
 		/// The hash of the submitted parent header doesn't correspond to the saved block hash of
 		/// the parent.
 		InvalidParentHeader,
-		/// Potentially invalid candidate.
-		CandidateCouldBeInvalid,
+		/// Disputed candidate that was concluded invalid.
+		CandidateConcludedInvalid,
 	}
 
 	/// Whether the paras inherent was included within this block.
@@ -238,14 +238,14 @@ pub mod pallet {
 			let backed_candidates = limit_backed_candidates::<T>(backed_candidates);
 			let backed_candidates_len = backed_candidates.len() as Weight;
 
-			// Refuse to back any candidates that are disputed or invalid.
+			// Refuse to back any candidates that were disputed and are concluded invalid.
 			for candidate in &backed_candidates {
 				ensure!(
-					!T::DisputesHandler::could_be_invalid(
+					!T::DisputesHandler::concluded_invalid(
 						current_session,
 						candidate.candidate.hash(),
 					),
-					Error::<T>::CandidateCouldBeInvalid,
+					Error::<T>::CandidateConcludedInvalid,
 				);
 			}