Backport 4229 Into v1.7.0 (#4288)

Backport of #4229 into the v1.7.0 release in order to support dependent
runtimes. This version of the SDK doesn't have
`UncheckedOnRuntimeUpgrade`, so I do it the "old way".

cumulus/pallets/collator-selection/src/lib.rs

@@ -119,7 +119,7 @@ pub mod pallet {
 	use sp_std::vec::Vec;
 
 	/// The current storage version.
-	const STORAGE_VERSION: StorageVersion = StorageVersion::new(1);
+	const STORAGE_VERSION: StorageVersion = StorageVersion::new(2);
 
 	type BalanceOf<T> =
 		<<T as Config>::Currency as Currency<<T as SystemConfig>::AccountId>>::Balance;
@@ -338,8 +338,8 @@ pub mod pallet {
 		fn integrity_test() {
 			assert!(T::MinEligibleCollators::get() > 0, "chain must require at least one collator");
 			assert!(
-				T::MaxInvulnerables::get().saturating_add(T::MaxCandidates::get())
-					>= T::MinEligibleCollators::get(),
+				T::MaxInvulnerables::get().saturating_add(T::MaxCandidates::get()) >=
+					T::MinEligibleCollators::get(),
 				"invulnerables and candidates must be able to satisfy collator demand"
 			);
 		}
@@ -374,8 +374,8 @@ pub mod pallet {
 			if new.is_empty() {
 				// Casting `u32` to `usize` should be safe on all machines running this.
 				ensure!(
-					CandidateList::<T>::decode_len().unwrap_or_default()
-						>= T::MinEligibleCollators::get() as usize,
+					CandidateList::<T>::decode_len().unwrap_or_default() >=
+						T::MinEligibleCollators::get() as usize,
 					Error::<T>::TooFewEligibleCollators
 				);
 			}
@@ -678,8 +678,8 @@ pub mod pallet {
 					} else if new_deposit < old_deposit {
 						// Casting `u32` to `usize` should be safe on all machines running this.
 						ensure!(
-							idx.saturating_add(<DesiredCandidates<T>>::get() as usize)
-								< candidate_count,
+							idx.saturating_add(<DesiredCandidates<T>>::get() as usize) <
+								candidate_count,
 							Error::<T>::InvalidUnreserve
 						);
 						T::Currency::unreserve(&who, old_deposit - new_deposit);

cumulus/pallets/collator-selection/src/migration.rs

@@ -20,6 +20,104 @@ use super::*;
 use frame_support::traits::OnRuntimeUpgrade;
 use log;
 
+/// Migrate to v2. Should have been part of <https://github.com/paritytech/polkadot-sdk/pull/1340>.
+pub mod v2 {
+	use super::*;
+	use frame_support::{
+		pallet_prelude::*,
+		storage_alias,
+		traits::{Currency, ReservableCurrency},
+	};
+	use sp_runtime::traits::{Saturating, Zero};
+	#[cfg(feature = "try-runtime")]
+	use sp_std::vec::Vec;
+
+	#[storage_alias]
+	pub type Candidates<T: Config> = StorageValue<
+		Pallet<T>,
+		BoundedVec<CandidateInfo<<T as frame_system::Config>::AccountId, <<T as Config>::Currency as Currency<<T as frame_system::Config>::AccountId>>::Balance>, <T as Config>::MaxCandidates>,
+		ValueQuery,
+	>;
+
+	/// Migrate to V2.
+	pub struct MigrationToV2<T>(sp_std::marker::PhantomData<T>);
+	impl<T: Config + pallet_balances::Config> OnRuntimeUpgrade for MigrationToV2<T> {
+		fn on_runtime_upgrade() -> Weight {
+			let on_chain_version = Pallet::<T>::on_chain_storage_version();
+			if on_chain_version == 1 {
+				let mut weight = Weight::zero();
+				let mut count: u64 = 0;
+				// candidates who exist under the old `Candidates` key
+				let candidates = Candidates::<T>::take();
+
+				// New candidates who have registered since the upgrade. Under normal circumstances,
+				// this should not exist because the migration should be applied when the upgrade
+				// happens. But in Polkadot/Kusama we messed this up, and people registered under
+				// `CandidateList` while their funds were locked in `Candidates`.
+				let new_candidate_list = CandidateList::<T>::get();
+				if new_candidate_list.len().is_zero() {
+					// The new list is empty, so this is essentially being applied correctly. We
+					// just put the candidates into the new storage item.
+					CandidateList::<T>::put(&candidates);
+					// 1 write for the new list
+					weight.saturating_accrue(T::DbWeight::get().reads_writes(0, 1));
+				} else {
+					// Oops, the runtime upgraded without the migration. There are new candidates in
+					// `CandidateList`. So, let's just refund the old ones and assume they have
+					// already started participating in the new system.
+					for candidate in candidates {
+						let err = T::Currency::unreserve(&candidate.who, candidate.deposit);
+						if err > Zero::zero() {
+							log::error!(
+								target: LOG_TARGET,
+								"{:?} balance was unable to be unreserved from {:?}",
+								err, &candidate.who,
+							);
+						}
+						count.saturating_inc();
+					}
+					weight.saturating_accrue(
+						<<T as pallet_balances::Config>::WeightInfo as pallet_balances::WeightInfo>::force_unreserve().saturating_mul(count.into()),
+					);
+				}
+
+				StorageVersion::new(2).put::<Pallet<T>>();
+
+				log::info!(
+					target: LOG_TARGET,
+					"Unreserved locked bond of {} candidates, upgraded storage to version 2",
+					count,
+				);
+
+				weight.saturating_accrue(T::DbWeight::get().reads_writes(3, 2));
+				weight
+			} else {
+				log::info!(
+					target: LOG_TARGET,
+					"Migration did not execute. This probably should be removed"
+				);
+				T::DbWeight::get().reads(1)
+			}
+		}
+
+		#[cfg(feature = "try-runtime")]
+		fn pre_upgrade() -> Result<Vec<u8>, sp_runtime::DispatchError> {
+			let number_of_candidates = Candidates::<T>::get().to_vec().len();
+			Ok((number_of_candidates as u32).encode())
+		}
+
+		#[cfg(feature = "try-runtime")]
+		fn post_upgrade(_number_of_candidates: Vec<u8>) -> Result<(), sp_runtime::DispatchError> {
+			let new_number_of_candidates = Candidates::<T>::get().to_vec().len();
+			assert_eq!(
+				new_number_of_candidates, 0 as usize,
+				"after migration, the candidates map should be empty"
+			);
+			Ok(())
+		}
+	}
+}
+
 /// Version 1 Migration
 /// This migration ensures that any existing `Invulnerables` storage lists are sorted.
 pub mod v1 {
@@ -90,3 +188,136 @@ pub mod v1 {
 		}
 	}
 }
+
+#[cfg(all(feature = "try-runtime", test))]
+mod tests {
+	use super::*;
+	use crate::{
+		migration::v2::Candidates,
+		mock::{new_test_ext, Balances, Test},
+	};
+	use frame_support::{
+		traits::{Currency, ReservableCurrency, StorageVersion},
+		BoundedVec,
+	};
+	use sp_runtime::traits::ConstU32;
+
+	#[test]
+	fn migrate_to_v2_with_new_candidates() {
+		new_test_ext().execute_with(|| {
+			let storage_version = StorageVersion::new(1);
+			storage_version.put::<Pallet<Test>>();
+
+			let one = 1u64;
+			let two = 2u64;
+			let three = 3u64;
+			let deposit = 10u64;
+
+			// Set balance to 100
+			Balances::make_free_balance_be(&one, 100u64);
+			Balances::make_free_balance_be(&two, 100u64);
+			Balances::make_free_balance_be(&three, 100u64);
+
+			// Reservations: 10 for the "old" candidacy and 10 for the "new"
+			Balances::reserve(&one, 10u64).unwrap(); // old
+			Balances::reserve(&two, 20u64).unwrap(); // old + new
+			Balances::reserve(&three, 10u64).unwrap(); // new
+
+			// Candidate info
+			let candidate_one = CandidateInfo { who: one, deposit };
+			let candidate_two = CandidateInfo { who: two, deposit };
+			let candidate_three = CandidateInfo { who: three, deposit };
+
+			// Storage lists
+			let bounded_candidates =
+				BoundedVec::<CandidateInfo<u64, u64>, ConstU32<20>>::try_from(vec![
+					candidate_one.clone(),
+					candidate_two.clone(),
+				])
+				.expect("it works");
+			let bounded_candidate_list =
+				BoundedVec::<CandidateInfo<u64, u64>, ConstU32<20>>::try_from(vec![
+					candidate_two.clone(),
+					candidate_three.clone(),
+				])
+				.expect("it works");
+
+			// Set storage
+			Candidates::<Test>::put(bounded_candidates);
+			CandidateList::<Test>::put(bounded_candidate_list.clone());
+
+			// Sanity check
+			assert_eq!(Balances::free_balance(one), 90);
+			assert_eq!(Balances::free_balance(two), 80);
+			assert_eq!(Balances::free_balance(three), 90);
+
+			// Run migration
+			v2::MigrationToV2::<Test>::on_runtime_upgrade();
+
+			let new_storage_version = StorageVersion::get::<Pallet<Test>>();
+			assert_eq!(new_storage_version, 2);
+
+			// 10 should have been unreserved from the old candidacy
+			assert_eq!(Balances::free_balance(one), 100);
+			assert_eq!(Balances::free_balance(two), 90);
+			assert_eq!(Balances::free_balance(three), 90);
+			// The storage item should be gone
+			assert!(Candidates::<Test>::get().is_empty());
+			// The new storage item should be preserved
+			assert_eq!(CandidateList::<Test>::get(), bounded_candidate_list);
+		});
+	}
+
+	#[test]
+	fn migrate_to_v2_without_new_candidates() {
+		new_test_ext().execute_with(|| {
+			let storage_version = StorageVersion::new(1);
+			storage_version.put::<Pallet<Test>>();
+
+			let one = 1u64;
+			let two = 2u64;
+			let deposit = 10u64;
+
+			// Set balance to 100
+			Balances::make_free_balance_be(&one, 100u64);
+			Balances::make_free_balance_be(&two, 100u64);
+
+			// Reservations
+			Balances::reserve(&one, 10u64).unwrap(); // old
+			Balances::reserve(&two, 10u64).unwrap(); // old
+
+			// Candidate info
+			let candidate_one = CandidateInfo { who: one, deposit };
+			let candidate_two = CandidateInfo { who: two, deposit };
+
+			// Storage lists
+			let bounded_candidates =
+				BoundedVec::<CandidateInfo<u64, u64>, ConstU32<20>>::try_from(vec![
+					candidate_one.clone(),
+					candidate_two.clone(),
+				])
+				.expect("it works");
+
+			// Set storage
+			Candidates::<Test>::put(bounded_candidates.clone());
+
+			// Sanity check
+			assert_eq!(Balances::free_balance(one), 90);
+			assert_eq!(Balances::free_balance(two), 90);
+
+			// Run migration
+			v2::MigrationToV2::<Test>::on_runtime_upgrade();
+
+			let new_storage_version = StorageVersion::get::<Pallet<Test>>();
+			assert_eq!(new_storage_version, 2);
+
+			// Nothing changes deposit-wise
+			assert_eq!(Balances::free_balance(one), 90);
+			assert_eq!(Balances::free_balance(two), 90);
+			// The storage item should be gone
+			assert!(Candidates::<Test>::get().is_empty());
+			// The new storage item should have the info now
+			assert_eq!(CandidateList::<Test>::get(), bounded_candidates);
+		});
+	}
+}

prdoc/1.7.0/pr_4288.prdoc

@@ -0,0 +1,10 @@
+title: "Fix Stuck Collator Funds"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Fixes stuck collator funds by providing a migration that should have been in PR 1340.
+
+crates:
+  - name: pallet-collator-selection
+    bump: patch