[Pools] Fix issues with member migration to DelegateStake (#4822)

## Context
Pool members using the old `TransferStake` strategy were able to
transfer all their funds to the pool. With `DelegateStake` changes, we
want to ensure similar behaviour by allowing members to delegate all
their stake to the pool.

## Changes
- Ensure all the balance including ED of an account can be delegated
(and used in the pool) by adding a provider for delegators.
- Gates calls that mutates the pool or pool member if they are in
unmigrated state. Closes
paritytech-secops/srlabs_findings#409.
- Adds remote test to migrate all pools and members to `DelegateStake`
which can be used with `Kusama` and `Polkadot` runtime state. closes
#4629.
- Add new runtime apis to read pool and member balance.

## Addressing possible migration errors 
Pool members migrating can run into two types of errors:
- Already Staking: If the pool member is already staking, we cannot
migrate them to `DelegateStake` since this may mean they are able to use
the same staked funds in the pool. Users would need to withdraw all
their funds from staking, in order to migrate their pool funds.
- Pool contribution below ED: For these cases transfer from pool account
to member account would fail. The affected users can top up their
accounts and redo migration.

Another error that was earlier possible was when member's free balance
is below ED. This PR adds a provider to delegator allowing all user
balance including ED can be contributed towards the pool. This helps
`1095` accounts in Polkadot and `41` accounts in Kusama to migrate now
which would have earlier failed.

## Results from RemoteExternalities Tests.

### Kusama
`Migration stats: success: 3017, direct_stakers: 361, unexpected_errors:
0`

### Polkadot
`Migration stats: success: 42859, direct_stakers: 643,
unexpected_errors: 0`

## TODO
- [x] Add runtime api for member total balance.
- [x] New
[issue](#5009) to reap
pool members with contribution below ED.
- [x] Add provider for delegators so whole balance including ED can be
held while contributing to pools.
- [x] Gate all pool extrinsics if pool/member is in non-migrated state.

---------

Co-authored-by: Gonçalo Pestana <g6pestana@gmail.com>

polkadot/runtime/westend/src/lib.rs

@@ -99,7 +99,7 @@ use sp_runtime::{
 		IdentityLookup, Keccak256, OpaqueKeys, SaturatedConversion, Verify,
 	},
 	transaction_validity::{TransactionPriority, TransactionSource, TransactionValidity},
-	ApplyExtrinsicResult, FixedU128, KeyTypeId, Perbill, Percent, Permill,
+	ApplyExtrinsicResult, FixedU128, KeyTypeId, Percent, Permill,
 };
 use sp_staking::SessionIndex;
 #[cfg(any(feature = "std", test))]
@@ -2476,6 +2476,14 @@ sp_api::impl_runtime_apis! {
 		fn member_needs_delegate_migration(member: AccountId) -> bool {
 			NominationPools::api_member_needs_delegate_migration(member)
 		}
+
+		fn member_total_balance(member: AccountId) -> Balance {
+			NominationPools::api_member_total_balance(member)
+		}
+
+		fn pool_balance(pool_id: pallet_nomination_pools::PoolId) -> Balance {
+			NominationPools::api_pool_balance(pool_id)
+		}
 	}
 
 	impl pallet_staking_runtime_api::StakingApi<Block, Balance, AccountId> for Runtime {
@@ -2776,45 +2784,6 @@ sp_api::impl_runtime_apis! {
 	}
 }
 
-#[cfg(all(test, feature = "try-runtime"))]
-mod remote_tests {
-	use super::*;
-	use frame_try_runtime::{runtime_decl_for_try_runtime::TryRuntime, UpgradeCheckSelect};
-	use remote_externalities::{
-		Builder, Mode, OfflineConfig, OnlineConfig, SnapshotConfig, Transport,
-	};
-	use std::env::var;
-
-	#[tokio::test]
-	async fn run_migrations() {
-		if var("RUN_MIGRATION_TESTS").is_err() {
-			return;
-		}
-
-		sp_tracing::try_init_simple();
-		let transport: Transport =
-			var("WS").unwrap_or("wss://westend-rpc.polkadot.io:443".to_string()).into();
-		let maybe_state_snapshot: Option<SnapshotConfig> = var("SNAP").map(|s| s.into()).ok();
-		let mut ext = Builder::<Block>::default()
-			.mode(if let Some(state_snapshot) = maybe_state_snapshot {
-				Mode::OfflineOrElseOnline(
-					OfflineConfig { state_snapshot: state_snapshot.clone() },
-					OnlineConfig {
-						transport,
-						state_snapshot: Some(state_snapshot),
-						..Default::default()
-					},
-				)
-			} else {
-				Mode::Online(OnlineConfig { transport, ..Default::default() })
-			})
-			.build()
-			.await
-			.unwrap();
-		ext.execute_with(|| Runtime::on_runtime_upgrade(UpgradeCheckSelect::PreAndPost));
-	}
-}
-
 mod clean_state_migration {
 	use super::Runtime;
 	#[cfg(feature = "try-runtime")]

polkadot/runtime/westend/src/tests.rs

@@ -99,3 +99,140 @@ fn check_treasury_pallet_id() {
 		westend_runtime_constants::TREASURY_PALLET_ID
 	);
 }
+
+#[cfg(all(test, feature = "try-runtime"))]
+mod remote_tests {
+	use super::*;
+	use frame_try_runtime::{runtime_decl_for_try_runtime::TryRuntime, UpgradeCheckSelect};
+	use remote_externalities::{
+		Builder, Mode, OfflineConfig, OnlineConfig, SnapshotConfig, Transport,
+	};
+	use std::env::var;
+
+	#[tokio::test]
+	async fn run_migrations() {
+		if var("RUN_MIGRATION_TESTS").is_err() {
+			return;
+		}
+
+		sp_tracing::try_init_simple();
+		let transport: Transport =
+			var("WS").unwrap_or("wss://westend-rpc.polkadot.io:443".to_string()).into();
+		let maybe_state_snapshot: Option<SnapshotConfig> = var("SNAP").map(|s| s.into()).ok();
+		let mut ext = Builder::<Block>::default()
+			.mode(if let Some(state_snapshot) = maybe_state_snapshot {
+				Mode::OfflineOrElseOnline(
+					OfflineConfig { state_snapshot: state_snapshot.clone() },
+					OnlineConfig {
+						transport,
+						state_snapshot: Some(state_snapshot),
+						..Default::default()
+					},
+				)
+			} else {
+				Mode::Online(OnlineConfig { transport, ..Default::default() })
+			})
+			.build()
+			.await
+			.unwrap();
+		ext.execute_with(|| Runtime::on_runtime_upgrade(UpgradeCheckSelect::PreAndPost));
+	}
+
+	#[tokio::test]
+	async fn delegate_stake_migration() {
+		// Intended to be run only manually.
+		if var("RUN_MIGRATION_TESTS").is_err() {
+			return;
+		}
+		use frame_support::assert_ok;
+		sp_tracing::try_init_simple();
+
+		let transport: Transport = var("WS").unwrap_or("ws://127.0.0.1:9900".to_string()).into();
+		let maybe_state_snapshot: Option<SnapshotConfig> = var("SNAP").map(|s| s.into()).ok();
+		let mut ext = Builder::<Block>::default()
+			.mode(if let Some(state_snapshot) = maybe_state_snapshot {
+				Mode::OfflineOrElseOnline(
+					OfflineConfig { state_snapshot: state_snapshot.clone() },
+					OnlineConfig {
+						transport,
+						state_snapshot: Some(state_snapshot),
+						pallets: vec![
+							"staking".into(),
+							"system".into(),
+							"balances".into(),
+							"nomination-pools".into(),
+							"delegated-staking".into(),
+						],
+						..Default::default()
+					},
+				)
+			} else {
+				Mode::Online(OnlineConfig { transport, ..Default::default() })
+			})
+			.build()
+			.await
+			.unwrap();
+		ext.execute_with(|| {
+			// create an account with some balance
+			let alice = AccountId::from([1u8; 32]);
+			use frame_support::traits::Currency;
+			let _ = Balances::deposit_creating(&alice, 100_000 * UNITS);
+
+			// iterate over all pools
+			pallet_nomination_pools::BondedPools::<Runtime>::iter_keys().for_each(|k| {
+				if pallet_nomination_pools::Pallet::<Runtime>::api_pool_needs_delegate_migration(k)
+				{
+					assert_ok!(
+						pallet_nomination_pools::Pallet::<Runtime>::migrate_pool_to_delegate_stake(
+							RuntimeOrigin::signed(alice.clone()).into(),
+							k,
+						)
+					);
+				}
+			});
+
+			// member migration stats
+			let mut success = 0;
+			let mut direct_stakers = 0;
+			let mut unexpected_errors = 0;
+
+			// iterate over all pool members
+			pallet_nomination_pools::PoolMembers::<Runtime>::iter_keys().for_each(|k| {
+				if pallet_nomination_pools::Pallet::<Runtime>::api_member_needs_delegate_migration(
+					k.clone(),
+				) {
+					// reasons migrations can fail:
+					let is_direct_staker = pallet_staking::Bonded::<Runtime>::contains_key(&k);
+
+					let migration = pallet_nomination_pools::Pallet::<Runtime>::migrate_delegation(
+						RuntimeOrigin::signed(alice.clone()).into(),
+						sp_runtime::MultiAddress::Id(k.clone()),
+					);
+
+					if is_direct_staker {
+						// if the member is a direct staker, the migration should fail until pool
+						// member unstakes all funds from pallet-staking.
+						direct_stakers += 1;
+						assert_eq!(
+							migration.unwrap_err(),
+							pallet_delegated_staking::Error::<Runtime>::AlreadyStaking.into()
+						);
+					} else if migration.is_err() {
+						unexpected_errors += 1;
+						log::error!(target: "remote_test", "Unexpected error {:?} while migrating {:?}", migration.unwrap_err(), k);
+					} else {
+						success += 1;
+					}
+				}
+			});
+
+			log::info!(
+				target: "remote_test",
+				"Migration stats: success: {}, direct_stakers: {}, unexpected_errors: {}",
+				success,
+				direct_stakers,
+				unexpected_errors
+			);
+		});
+	}
+}

prdoc/pr_4822.prdoc

@@ -0,0 +1,25 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Ensure as many as possible pool members can migrate to `DelegateStake`
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      1. Allows pool members to use their total balance while joining pool with `DelegateStake`.
+      2. Gates call mutating pool or member in unmigrated state.
+      3. Runtime apis for reading pool and member balance.
+
+crates:
+  - name: westend-runtime
+    bump: minor
+  - name: kitchensink-runtime
+    bump: patch
+  - name: pallet-delegated-staking
+    bump: patch
+  - name: pallet-nomination-pools
+    bump: minor
+  - name: sp-staking
+    bump: patch
+  - name: pallet-nomination-pools-runtime-api
+    bump: minor

substrate/bin/node/runtime/src/lib.rs

@@ -2784,6 +2784,14 @@ impl_runtime_apis! {
 		fn member_needs_delegate_migration(member: AccountId) -> bool {
 			NominationPools::api_member_needs_delegate_migration(member)
 		}
+
+		fn member_total_balance(member: AccountId) -> Balance {
+			NominationPools::api_member_total_balance(member)
+		}
+
+		fn pool_balance(pool_id: pallet_nomination_pools::PoolId) -> Balance {
+			NominationPools::api_pool_balance(pool_id)
+		}
 	}
 
 	impl pallet_staking_runtime_api::StakingApi<Block, Balance, AccountId> for Runtime {

substrate/frame/delegated-staking/src/impls.rs

@@ -19,7 +19,7 @@
 //! Implementations of public traits, namely [`DelegationInterface`] and [`OnStakingUpdate`].
 
 use super::*;
-use sp_staking::{Agent, DelegationInterface, DelegationMigrator, Delegator, OnStakingUpdate};
+use sp_staking::{DelegationInterface, DelegationMigrator, OnStakingUpdate};
 
 impl<T: Config> DelegationInterface for Pallet<T> {
 	type Balance = BalanceOf<T>;