[FRAME] Make core-fellowship ans salary work for swapped members (#3156)

Fixup for https://github.com/paritytech/polkadot-sdk/pull/2587 to make
the `core-fellowship` crate work with swapped members.

Adds a `MemberSwappedHandler` to the `ranked-collective` pallet that are
implemented by `core-fellowship+salary`.
There is are exhaustive tests
[here](https://github.com/paritytech/polkadot-sdk/blob/72aa7ac17a0e5b16faab5d2992aa2db2e01b05d0/substrate/frame/core-fellowship/src/tests/integration.rs#L338)
and
[here](https://github.com/paritytech/polkadot-sdk/blob/ab3cdb05a5ebc1ff841f8dda67edef0ea40bbba5/substrate/frame/salary/src/tests/integration.rs#L224)
to check that adding member `1` is equivalent to adding member `0` and
then swapping.

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Cargo.lock

@@ -9657,6 +9657,7 @@ dependencies = [
  "frame-support",
  "frame-system",
  "log",
+ "pallet-ranked-collective",
  "parity-scale-codec",
  "scale-info",
  "sp-arithmetic",
@@ -10462,6 +10463,7 @@ dependencies = [
  "frame-benchmarking",
  "frame-support",
  "frame-system",
+ "impl-trait-for-tuples",
  "log",
  "parity-scale-codec",
  "scale-info",
@@ -10589,6 +10591,7 @@ dependencies = [
  "frame-support",
  "frame-system",
  "log",
+ "pallet-ranked-collective",
  "parity-scale-codec",
  "scale-info",
  "sp-arithmetic",

cumulus/parachains/runtimes/collectives/collectives-westend/src/ambassador/mod.rs

@@ -113,7 +113,10 @@ impl pallet_ranked_collective::Config<AmbassadorCollectiveInstance> for Runtime
 	type ExchangeOrigin = ExchangeOrigin;
 	type Polls = AmbassadorReferenda;
 	type MinRankOfClass = sp_runtime::traits::Identity;
+	type MemberSwappedHandler = (crate::AmbassadorCore, crate::AmbassadorSalary);
 	type VoteWeight = pallet_ranked_collective::Linear;
+	#[cfg(feature = "runtime-benchmarks")]
+	type BenchmarkSetup = (crate::AmbassadorCore, crate::AmbassadorSalary);
 }
 
 parameter_types! {

cumulus/parachains/runtimes/collectives/collectives-westend/src/fellowship/mod.rs

@@ -141,7 +141,10 @@ impl pallet_ranked_collective::Config<FellowshipCollectiveInstance> for Runtime
 		EitherOf<EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>, Fellows>;
 	type Polls = FellowshipReferenda;
 	type MinRankOfClass = tracks::MinRankOfClass;
+	type MemberSwappedHandler = (crate::FellowshipCore, crate::FellowshipSalary);
 	type VoteWeight = pallet_ranked_collective::Geometric;
+	#[cfg(feature = "runtime-benchmarks")]
+	type BenchmarkSetup = (crate::FellowshipCore, crate::FellowshipSalary);
 }
 
 pub type FellowshipCoreInstance = pallet_core_fellowship::Instance1;

polkadot/runtime/rococo/src/governance/fellowship.rs

@@ -344,5 +344,8 @@ impl pallet_ranked_collective::Config<FellowshipCollectiveInstance> for Runtime
 		EitherOf<EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>, Fellows>;
 	type Polls = FellowshipReferenda;
 	type MinRankOfClass = sp_runtime::traits::Identity;
+	type MemberSwappedHandler = ();
 	type VoteWeight = pallet_ranked_collective::Geometric;
+	#[cfg(feature = "runtime-benchmarks")]
+	type BenchmarkSetup = ();
 }

prdoc/pr_3156.prdoc

@@ -0,0 +1,13 @@
+title: "Adapt core-fellowship and salary pallets for swapped members"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      The ranked-collective pallet got the ability to swap members but the core-fellowship and
+      salary pallets would not be notified of this change. This MR adds `MemberSwappedHandler` to
+      the collective that is implemented by both pallets.
+
+crates:
+  - name: "pallet-ranked-collective"
+  - name: "pallet-core-fellowship"
+  - name: "pallet-salary"

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

@@ -1019,6 +1019,9 @@ impl pallet_ranked_collective::Config for Runtime {
 	type Polls = RankedPolls;
 	type MinRankOfClass = traits::Identity;
 	type VoteWeight = pallet_ranked_collective::Geometric;
+	type MemberSwappedHandler = (CoreFellowship, Salary);
+	#[cfg(feature = "runtime-benchmarks")]
+	type BenchmarkSetup = (CoreFellowship, Salary);
 }
 
 impl pallet_remark::Config for Runtime {

substrate/frame/core-fellowship/Cargo.toml

@@ -27,15 +27,18 @@ sp-core = { path = "../../primitives/core", default-features = false }
 sp-io = { path = "../../primitives/io", default-features = false }
 sp-runtime = { path = "../../primitives/runtime", default-features = false }
 sp-std = { path = "../../primitives/std", default-features = false }
+pallet-ranked-collective = { path = "../ranked-collective", default-features = false, optional = true }
 
 [features]
 default = ["std"]
 std = [
 	"codec/std",
 	"frame-benchmarking?/std",
+	"frame-support/experimental",
 	"frame-support/std",
 	"frame-system/std",
 	"log/std",
+	"pallet-ranked-collective/std",
 	"scale-info/std",
 	"sp-arithmetic/std",
 	"sp-core/std",
@@ -47,10 +50,12 @@ runtime-benchmarks = [
 	"frame-benchmarking/runtime-benchmarks",
 	"frame-support/runtime-benchmarks",
 	"frame-system/runtime-benchmarks",
+	"pallet-ranked-collective/runtime-benchmarks",
 	"sp-runtime/runtime-benchmarks",
 ]
 try-runtime = [
 	"frame-support/try-runtime",
 	"frame-system/try-runtime",
+	"pallet-ranked-collective?/try-runtime",
 	"sp-runtime/try-runtime",
 ]

substrate/frame/core-fellowship/src/benchmarking.rs

@@ -227,7 +227,7 @@ mod benchmarks {
 
 	impl_benchmark_test_suite! {
 		CoreFellowship,
-		crate::tests::new_test_ext(),
-		crate::tests::Test,
+		crate::tests::unit::new_test_ext(),
+		crate::tests::unit::Test,
 	}
 }

substrate/frame/core-fellowship/src/lib.rs

@@ -65,10 +65,12 @@ use sp_runtime::RuntimeDebug;
 use sp_std::{marker::PhantomData, prelude::*};
 
 use frame_support::{
+	defensive,
 	dispatch::DispatchResultWithPostInfo,
 	ensure, impl_ensure_origin_with_arg_ignoring_arg,
 	traits::{
 		tokens::Balance as BalanceTrait, EnsureOrigin, EnsureOriginWithArg, Get, RankedMembers,
+		RankedMembersSwapHandler,
 	},
 	BoundedVec,
 };
@@ -249,6 +251,8 @@ pub mod pallet {
 		},
 		/// Pre-ranked account has been inducted at their current rank.
 		Imported { who: T::AccountId, rank: RankOf<T, I> },
+		/// A member had its AccountId swapped.
+		Swapped { who: T::AccountId, new_who: T::AccountId },
 	}
 
 	#[pallet::error]
@@ -603,3 +607,38 @@ impl_ensure_origin_with_arg_ignoring_arg! {
 		EnsureOriginWithArg<T::RuntimeOrigin, A> for EnsureInducted<T, I, MIN_RANK>
 	{}
 }
+
+impl<T: Config<I>, I: 'static> RankedMembersSwapHandler<T::AccountId, u16> for Pallet<T, I> {
+	fn swapped(old: &T::AccountId, new: &T::AccountId, _rank: u16) {
+		if old == new {
+			defensive!("Should not try to swap with self");
+			return
+		}
+		if !Member::<T, I>::contains_key(old) {
+			defensive!("Should not try to swap non-member");
+			return
+		}
+		if Member::<T, I>::contains_key(new) {
+			defensive!("Should not try to overwrite existing member");
+			return
+		}
+
+		if let Some(member) = Member::<T, I>::take(old) {
+			Member::<T, I>::insert(new, member);
+		}
+		if let Some(we) = MemberEvidence::<T, I>::take(old) {
+			MemberEvidence::<T, I>::insert(new, we);
+		}
+
+		Self::deposit_event(Event::<T, I>::Swapped { who: old.clone(), new_who: new.clone() });
+	}
+}
+
+#[cfg(feature = "runtime-benchmarks")]
+impl<T: Config<I>, I: 'static>
+	pallet_ranked_collective::BenchmarkSetup<<T as frame_system::Config>::AccountId> for Pallet<T, I>
+{
+	fn ensure_member(who: &<T as frame_system::Config>::AccountId) {
+		Self::import(frame_system::RawOrigin::Signed(who.clone()).into()).unwrap();
+	}
+}

substrate/frame/core-fellowship/src/tests/integration.rs

@@ -0,0 +1,278 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Integration test together with the ranked-collective pallet.
+
+use frame_support::{
+	assert_noop, assert_ok, derive_impl, hypothetically, ord_parameter_types,
+	pallet_prelude::Weight,
+	parameter_types,
+	traits::{ConstU16, EitherOf, IsInVec, MapSuccess, PollStatus, Polling, TryMapSuccess},
+};
+use frame_system::EnsureSignedBy;
+use pallet_ranked_collective::{EnsureRanked, Geometric, Rank, TallyOf, Votes};
+use sp_core::Get;
+use sp_runtime::{
+	traits::{Convert, ReduceBy, TryMorphInto},
+	BuildStorage, DispatchError,
+};
+type Class = Rank;
+
+use crate as pallet_core_fellowship;
+use crate::*;
+
+type Block = frame_system::mocking::MockBlock<Test>;
+
+frame_support::construct_runtime!(
+	pub enum Test
+	{
+		System: frame_system,
+		CoreFellowship: pallet_core_fellowship,
+		Club: pallet_ranked_collective,
+	}
+);
+
+parameter_types! {
+	pub BlockWeights: frame_system::limits::BlockWeights =
+		frame_system::limits::BlockWeights::simple_max(Weight::from_parts(1_000_000, u64::max_value()));
+}
+
+#[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
+impl frame_system::Config for Test {
+	type Block = Block;
+}
+
+parameter_types! {
+	pub static MinRankOfClassDelta: Rank = 0;
+}
+
+parameter_types! {
+	pub ZeroToNine: Vec<u64> = vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
+	pub EvidenceSize: u32 = 1024;
+}
+ord_parameter_types! {
+	pub const One: u64 = 1;
+}
+
+impl Config for Test {
+	type WeightInfo = ();
+	type RuntimeEvent = RuntimeEvent;
+	type Members = Club;
+	type Balance = u64;
+	type ParamsOrigin = EnsureSignedBy<One, u64>;
+	type InductOrigin = EnsureInducted<Test, (), 1>;
+	type ApproveOrigin = TryMapSuccess<EnsureSignedBy<IsInVec<ZeroToNine>, u64>, TryMorphInto<u16>>;
+	type PromoteOrigin = TryMapSuccess<EnsureSignedBy<IsInVec<ZeroToNine>, u64>, TryMorphInto<u16>>;
+	type EvidenceSize = EvidenceSize;
+}
+
+pub struct TestPolls;
+impl Polling<TallyOf<Test>> for TestPolls {
+	type Index = u8;
+	type Votes = Votes;
+	type Moment = u64;
+	type Class = Class;
+
+	fn classes() -> Vec<Self::Class> {
+		unimplemented!()
+	}
+	fn as_ongoing(_: u8) -> Option<(TallyOf<Test>, Self::Class)> {
+		unimplemented!()
+	}
+	fn access_poll<R>(
+		_: Self::Index,
+		_: impl FnOnce(PollStatus<&mut TallyOf<Test>, Self::Moment, Self::Class>) -> R,
+	) -> R {
+		unimplemented!()
+	}
+	fn try_access_poll<R>(
+		_: Self::Index,
+		_: impl FnOnce(
+			PollStatus<&mut TallyOf<Test>, Self::Moment, Self::Class>,
+		) -> Result<R, DispatchError>,
+	) -> Result<R, DispatchError> {
+		unimplemented!()
+	}
+
+	#[cfg(feature = "runtime-benchmarks")]
+	fn create_ongoing(_: Self::Class) -> Result<Self::Index, ()> {
+		unimplemented!()
+	}
+
+	#[cfg(feature = "runtime-benchmarks")]
+	fn end_ongoing(_: Self::Index, _: bool) -> Result<(), ()> {
+		unimplemented!()
+	}
+}
+
+/// Convert the tally class into the minimum rank required to vote on the poll.
+/// MinRank(Class) = Class - Delta
+pub struct MinRankOfClass<Delta>(PhantomData<Delta>);
+impl<Delta: Get<Rank>> Convert<Class, Rank> for MinRankOfClass<Delta> {
+	fn convert(a: Class) -> Rank {
+		a.saturating_sub(Delta::get())
+	}
+}
+
+impl pallet_ranked_collective::Config for Test {
+	type WeightInfo = ();
+	type RuntimeEvent = RuntimeEvent;
+	type PromoteOrigin = EitherOf<
+		// Root can promote arbitrarily.
+		frame_system::EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>,
+		// Members can promote up to the rank of 2 below them.
+		MapSuccess<EnsureRanked<Test, (), 2>, ReduceBy<ConstU16<2>>>,
+	>;
+	type DemoteOrigin = EitherOf<
+		// Root can demote arbitrarily.
+		frame_system::EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>,
+		// Members can demote up to the rank of 3 below them.
+		MapSuccess<EnsureRanked<Test, (), 3>, ReduceBy<ConstU16<3>>>,
+	>;
+	type ExchangeOrigin = EitherOf<
+		// Root can exchange arbitrarily.
+		frame_system::EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>,
+		// Members can exchange up to the rank of 2 below them.
+		MapSuccess<EnsureRanked<Test, (), 2>, ReduceBy<ConstU16<2>>>,
+	>;
+	type Polls = TestPolls;
+	type MinRankOfClass = MinRankOfClass<MinRankOfClassDelta>;
+	type MemberSwappedHandler = CoreFellowship;
+	type VoteWeight = Geometric;
+	#[cfg(feature = "runtime-benchmarks")]
+	type BenchmarkSetup = CoreFellowship;
+}
+
+pub fn new_test_ext() -> sp_io::TestExternalities {
+	let t = frame_system::GenesisConfig::<Test>::default().build_storage().unwrap();
+	let mut ext = sp_io::TestExternalities::new(t);
+	ext.execute_with(|| {
+		let params = ParamsType {
+			active_salary: [10, 20, 30, 40, 50, 60, 70, 80, 90],
+			passive_salary: [1, 2, 3, 4, 5, 6, 7, 8, 9],
+			demotion_period: [2, 4, 6, 8, 10, 12, 14, 16, 18],
+			min_promotion_period: [3, 6, 9, 12, 15, 18, 21, 24, 27],
+			offboard_timeout: 1,
+		};
+		assert_ok!(CoreFellowship::set_params(signed(1), Box::new(params)));
+		System::set_block_number(1);
+	});
+	ext
+}
+
+fn promote_n_times(acc: u64, r: u16) {
+	for _ in 0..r {
+		assert_ok!(Club::promote_member(RuntimeOrigin::root(), acc));
+	}
+}
+
+fn signed(who: u64) -> RuntimeOrigin {
+	RuntimeOrigin::signed(who)
+}
+
+fn assert_last_event(generic_event: <Test as Config>::RuntimeEvent) {
+	let events = frame_system::Pallet::<Test>::events();
+	let system_event: <Test as frame_system::Config>::RuntimeEvent = generic_event.into();
+	let frame_system::EventRecord { event, .. } = events.last().expect("Event expected");
+	assert_eq!(event, &system_event.into());
+}
+
+fn evidence(e: u32) -> Evidence<Test, ()> {
+	e.encode()
+		.into_iter()
+		.cycle()
+		.take(1024)
+		.collect::<Vec<_>>()
+		.try_into()
+		.expect("Static length matches")
+}
+
+#[test]
+fn swap_simple_works() {
+	new_test_ext().execute_with(|| {
+		for i in 0u16..9 {
+			let acc = i as u64;
+
+			assert_ok!(Club::add_member(RuntimeOrigin::root(), acc));
+			promote_n_times(acc, i);
+			assert_ok!(CoreFellowship::import(signed(acc)));
+
+			// Swapping normally works:
+			assert_ok!(Club::exchange_member(RuntimeOrigin::root(), acc, acc + 10));
+			assert_last_event(Event::Swapped { who: acc, new_who: acc + 10 }.into());
+		}
+	});
+}
+
+/// Exhaustively test that adding member `1` is equivalent to adding member `0` and then swapping.
+///
+/// The member also submits evidence before the swap.
+#[test]
+fn swap_exhaustive_works() {
+	new_test_ext().execute_with(|| {
+		let root_add = hypothetically!({
+			assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
+			promote_n_times(1, 4);
+			assert_ok!(CoreFellowship::import(signed(1)));
+			assert_ok!(CoreFellowship::submit_evidence(signed(1), Wish::Retention, evidence(1)));
+
+			// The events mess up the storage root:
+			System::reset_events();
+			sp_io::storage::root(sp_runtime::StateVersion::V1)
+		});
+
+		let root_swap = hypothetically!({
+			assert_ok!(Club::add_member(RuntimeOrigin::root(), 0));
+			promote_n_times(0, 4);
+			assert_ok!(CoreFellowship::import(signed(0)));
+			assert_ok!(CoreFellowship::submit_evidence(signed(0), Wish::Retention, evidence(1)));
+
+			// Now we swap:
+			assert_ok!(Club::exchange_member(RuntimeOrigin::root(), 0, 1));
+
+			System::reset_events();
+			sp_io::storage::root(sp_runtime::StateVersion::V1)
+		});
+
+		assert_eq!(root_add, root_swap);
+		// Ensure that we dont compare trivial stuff like `()` from a type error above.
+		assert_eq!(root_add.len(), 32);
+	});
+}
+
+#[test]
+fn swap_bad_noops() {
+	new_test_ext().execute_with(|| {
+		assert_ok!(Club::add_member(RuntimeOrigin::root(), 0));
+		promote_n_times(0, 0);
+		assert_ok!(CoreFellowship::import(signed(0)));
+		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
+		promote_n_times(1, 1);
+		assert_ok!(CoreFellowship::import(signed(1)));
+
+		// Swapping for another member is a noop:
+		assert_noop!(
+			Club::exchange_member(RuntimeOrigin::root(), 0, 1),
+			pallet_ranked_collective::Error::<Test>::AlreadyMember
+		);
+		// Swapping for the same member is a noop:
+		assert_noop!(
+			Club::exchange_member(RuntimeOrigin::root(), 0, 0),
+			pallet_ranked_collective::Error::<Test>::SameMember
+		);
+	});
+}

substrate/frame/core-fellowship/src/tests/mod.rs

@@ -0,0 +1,23 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#![cfg(test)]
+
+//! Tests for this crate.
+
+pub(crate) mod integration;
+pub(crate) mod unit;

substrate/frame/core-fellowship/src/tests/unit.rs

@@ -23,18 +23,14 @@ use frame_support::{
 	assert_noop, assert_ok, derive_impl, ord_parameter_types,
 	pallet_prelude::Weight,
 	parameter_types,
-	traits::{tokens::GetSalary, ConstU32, ConstU64, Everything, IsInVec, TryMapSuccess},
+	traits::{tokens::GetSalary, ConstU32, IsInVec, TryMapSuccess},
 };
 use frame_system::EnsureSignedBy;
-use sp_core::H256;
-use sp_runtime::{
-	traits::{BlakeTwo256, IdentityLookup, TryMorphInto},
-	BuildStorage, DispatchError, DispatchResult,
-};
+use sp_runtime::{traits::TryMorphInto, BuildStorage, DispatchError, DispatchResult};
 use sp_std::cell::RefCell;
 
-use super::*;
 use crate as pallet_core_fellowship;
+use crate::*;
 
 type Block = frame_system::mocking::MockBlock<Test>;
 
@@ -53,29 +49,7 @@ parameter_types! {
 
 #[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
 impl frame_system::Config for Test {
-	type BaseCallFilter = Everything;
-	type BlockWeights = ();
-	type BlockLength = ();
-	type DbWeight = ();
-	type RuntimeOrigin = RuntimeOrigin;
-	type Nonce = u64;
-	type RuntimeCall = RuntimeCall;
-	type Hash = H256;
-	type Hashing = BlakeTwo256;
-	type AccountId = u64;
-	type Lookup = IdentityLookup<Self::AccountId>;
 	type Block = Block;
-	type RuntimeEvent = RuntimeEvent;
-	type BlockHashCount = ConstU64<250>;
-	type Version = ();
-	type PalletInfo = PalletInfo;
-	type AccountData = ();
-	type OnNewAccount = ();
-	type OnKilledAccount = ();
-	type SystemWeightInfo = ();
-	type SS58Prefix = ();
-	type OnSetCode = ();
-	type MaxConsumers = ConstU32<16>;
 }
 
 thread_local! {

substrate/frame/ranked-collective/Cargo.toml

@@ -27,6 +27,7 @@ sp-core = { path = "../../primitives/core", default-features = false }
 sp-io = { path = "../../primitives/io", default-features = false }
 sp-runtime = { path = "../../primitives/runtime", default-features = false }
 sp-std = { path = "../../primitives/std", default-features = false }
+impl-trait-for-tuples = "0.2.2"
 
 [features]
 default = ["std"]

substrate/frame/ranked-collective/src/benchmarking.rs

@@ -33,6 +33,10 @@ fn assert_last_event<T: Config<I>, I: 'static>(generic_event: <T as Config<I>>::
 	frame_system::Pallet::<T>::assert_last_event(generic_event.into());
 }
 
+fn assert_has_event<T: Config<I>, I: 'static>(generic_event: <T as Config<I>>::RuntimeEvent) {
+	frame_system::Pallet::<T>::assert_has_event(generic_event.into());
+}
+
 fn make_member<T: Config<I>, I: 'static>(rank: Rank) -> T::AccountId {
 	let who = account::<T::AccountId>("member", MemberCount::<T, I>::get(0), SEED);
 	let who_lookup = T::Lookup::unlookup(who.clone());
@@ -175,17 +179,18 @@ benchmarks_instance_pallet! {
 
 	exchange_member {
 		let who = make_member::<T, I>(1);
+		T::BenchmarkSetup::ensure_member(&who);
 		let who_lookup = T::Lookup::unlookup(who.clone());
 		let new_who = account::<T::AccountId>("new-member", 0, SEED);
 		let new_who_lookup = T::Lookup::unlookup(new_who.clone());
 		let origin =
 			T::ExchangeOrigin::try_successful_origin().map_err(|_| BenchmarkError::Weightless)?;
-		let call = Call::<T, I>::exchange_member { who: who_lookup, new_who:new_who_lookup};
+		let call = Call::<T, I>::exchange_member { who: who_lookup, new_who: new_who_lookup };
 	}: { call.dispatch_bypass_filter(origin)? }
 	verify {
 		assert_eq!(Members::<T, I>::get(&new_who).unwrap().rank, 1);
 		assert_eq!(Members::<T, I>::get(&who), None);
-		assert_last_event::<T, I>(Event::MemberExchanged { who, new_who }.into());
+		assert_has_event::<T, I>(Event::MemberExchanged { who, new_who }.into());
 	}
 
 	impl_benchmark_test_suite!(RankedCollective, crate::tests::new_test_ext(), crate::tests::Test);

substrate/frame/ranked-collective/src/lib.rs

@@ -54,7 +54,10 @@ use sp_std::{marker::PhantomData, prelude::*};
 use frame_support::{
 	dispatch::{DispatchResultWithPostInfo, PostDispatchInfo},
 	ensure, impl_ensure_origin_with_arg_ignoring_arg,
-	traits::{EnsureOrigin, EnsureOriginWithArg, PollStatus, Polling, RankedMembers, VoteTally},
+	traits::{
+		EnsureOrigin, EnsureOriginWithArg, PollStatus, Polling, RankedMembers,
+		RankedMembersSwapHandler, VoteTally,
+	},
 	CloneNoBound, EqNoBound, PartialEqNoBound, RuntimeDebugNoBound,
 };
 
@@ -365,6 +368,13 @@ impl_ensure_origin_with_arg_ignoring_arg! {
 	{}
 }
 
+/// Helper functions to setup benchmarking.
+#[impl_trait_for_tuples::impl_for_tuples(8)]
+pub trait BenchmarkSetup<AccountId> {
+	/// Ensure that this member is registered correctly.
+	fn ensure_member(acc: &AccountId);
+}
+
 #[frame_support::pallet]
 pub mod pallet {
 	use super::*;
@@ -402,11 +412,21 @@ pub mod pallet {
 		/// "a rank of at least the poll class".
 		type MinRankOfClass: Convert<ClassOf<Self, I>, Rank>;
 
+		/// An external handler that will be notified when two members are swapped.
+		type MemberSwappedHandler: RankedMembersSwapHandler<
+			<Pallet<Self, I> as RankedMembers>::AccountId,
+			<Pallet<Self, I> as RankedMembers>::Rank,
+		>;
+
 		/// Convert a rank_delta into a number of votes the rank gets.
 		///
 		/// Rank_delta is defined as the number of ranks above the minimum required to take part
 		/// in the poll.
 		type VoteWeight: Convert<Rank, Votes>;
+
+		/// Setup a member for benchmarking.
+		#[cfg(feature = "runtime-benchmarks")]
+		type BenchmarkSetup: BenchmarkSetup<Self::AccountId>;
 	}
 
 	/// The number of members in the collective who have at least the rank according to the index
@@ -679,7 +699,12 @@ pub mod pallet {
 			Self::do_remove_member_from_rank(&who, rank)?;
 			Self::do_add_member_to_rank(new_who.clone(), rank, false)?;
 
-			Self::deposit_event(Event::MemberExchanged { who, new_who });
+			Self::deposit_event(Event::MemberExchanged {
+				who: who.clone(),
+				new_who: new_who.clone(),
+			});
+			T::MemberSwappedHandler::swapped(&who, &new_who, rank);
+
 			Ok(())
 		}
 	}

substrate/frame/ranked-collective/src/tests.rs

@@ -172,7 +172,10 @@ impl Config for Test {
 	>;
 	type Polls = TestPolls;
 	type MinRankOfClass = MinRankOfClass<MinRankOfClassDelta>;
+	type MemberSwappedHandler = ();
 	type VoteWeight = Geometric;
+	#[cfg(feature = "runtime-benchmarks")]
+	type BenchmarkSetup = ();
 }
 
 pub fn new_test_ext() -> sp_io::TestExternalities {
@@ -602,3 +605,21 @@ fn exchange_member_works() {
 		);
 	});
 }
+
+#[test]
+fn exchange_member_same_noops() {
+	new_test_ext().execute_with(|| {
+		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
+		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
+		assert_ok!(Club::add_member(RuntimeOrigin::root(), 2));
+		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));
+
+		// Swapping the same accounts is a noop:
+		assert_noop!(Club::exchange_member(RuntimeOrigin::root(), 1, 1), Error::<Test>::SameMember);
+		// Swapping with a different member is a noop:
+		assert_noop!(
+			Club::exchange_member(RuntimeOrigin::root(), 1, 2),
+			Error::<Test>::AlreadyMember
+		);
+	});
+}

substrate/frame/salary/Cargo.toml

@@ -27,15 +27,18 @@ sp-core = { path = "../../primitives/core", default-features = false }
 sp-io = { path = "../../primitives/io", default-features = false }
 sp-runtime = { path = "../../primitives/runtime", default-features = false }
 sp-std = { path = "../../primitives/std", default-features = false }
+pallet-ranked-collective = { path = "../ranked-collective", default-features = false, optional = true }
 
 [features]
 default = ["std"]
 std = [
 	"codec/std",
 	"frame-benchmarking?/std",
+	"frame-support/experimental",
 	"frame-support/std",
 	"frame-system/std",
 	"log/std",
+	"pallet-ranked-collective/std",
 	"scale-info/std",
 	"sp-arithmetic/std",
 	"sp-core/std",
@@ -47,10 +50,12 @@ runtime-benchmarks = [
 	"frame-benchmarking/runtime-benchmarks",
 	"frame-support/runtime-benchmarks",
 	"frame-system/runtime-benchmarks",
+	"pallet-ranked-collective/runtime-benchmarks",
 	"sp-runtime/runtime-benchmarks",
 ]
 try-runtime = [
 	"frame-support/try-runtime",
 	"frame-system/try-runtime",
+	"pallet-ranked-collective?/try-runtime",
 	"sp-runtime/try-runtime",
 ]

substrate/frame/salary/src/benchmarking.rs

@@ -177,7 +177,7 @@ mod benchmarks {
 
 	impl_benchmark_test_suite! {
 		Salary,
-		crate::tests::new_test_ext(),
-		crate::tests::Test,
+		crate::tests::unit::new_test_ext(),
+		crate::tests::unit::Test,
 	}
 }

substrate/frame/salary/src/lib.rs

@@ -27,11 +27,12 @@ use sp_runtime::{Perbill, RuntimeDebug};
 use sp_std::{marker::PhantomData, prelude::*};
 
 use frame_support::{
+	defensive,
 	dispatch::DispatchResultWithPostInfo,
 	ensure,
 	traits::{
 		tokens::{GetSalary, Pay, PaymentStatus},
-		RankedMembers,
+		RankedMembers, RankedMembersSwapHandler,
 	},
 };
 
@@ -173,6 +174,8 @@ pub mod pallet {
 		},
 		/// The next cycle begins.
 		CycleStarted { index: CycleIndexOf<T> },
+		/// A member swapped their account.
+		Swapped { who: T::AccountId, new_who: T::AccountId },
 	}
 
 	#[pallet::error]
@@ -447,3 +450,40 @@ pub mod pallet {
 		}
 	}
 }
+
+impl<T: Config<I>, I: 'static>
+	RankedMembersSwapHandler<T::AccountId, <T::Members as RankedMembers>::Rank> for Pallet<T, I>
+{
+	fn swapped(
+		who: &T::AccountId,
+		new_who: &T::AccountId,
+		_rank: <T::Members as RankedMembers>::Rank,
+	) {
+		if who == new_who {
+			defensive!("Should not try to swap with self");
+			return
+		}
+		if Claimant::<T, I>::contains_key(new_who) {
+			defensive!("Should not try to overwrite existing claimant");
+			return
+		}
+
+		let Some(claimant) = Claimant::<T, I>::take(who) else {
+			frame_support::defensive!("Claimant should exist when swapping");
+			return;
+		};
+
+		Claimant::<T, I>::insert(new_who, claimant);
+		Self::deposit_event(Event::<T, I>::Swapped { who: who.clone(), new_who: new_who.clone() });
+	}
+}
+
+#[cfg(feature = "runtime-benchmarks")]
+impl<T: Config<I>, I: 'static>
+	pallet_ranked_collective::BenchmarkSetup<<T as frame_system::Config>::AccountId> for Pallet<T, I>
+{
+	fn ensure_member(who: &<T as frame_system::Config>::AccountId) {
+		Self::init(frame_system::RawOrigin::Signed(who.clone()).into()).unwrap();
+		Self::induct(frame_system::RawOrigin::Signed(who.clone()).into()).unwrap();
+	}
+}

substrate/frame/salary/src/tests/integration.rs

@@ -0,0 +1,278 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! The crate's tests.
+
+use frame_support::{
+	assert_noop, assert_ok, derive_impl, hypothetically,
+	pallet_prelude::Weight,
+	parameter_types,
+	traits::{ConstU64, EitherOf, MapSuccess, PollStatus, Polling},
+};
+use pallet_ranked_collective::{EnsureRanked, Geometric, TallyOf, Votes};
+use sp_core::{ConstU16, Get};
+use sp_runtime::{
+	traits::{Convert, ReduceBy},
+	BuildStorage, DispatchError,
+};
+
+use crate as pallet_salary;
+use crate::*;
+
+type Rank = u16;
+type Block = frame_system::mocking::MockBlock<Test>;
+
+frame_support::construct_runtime!(
+	pub enum Test
+	{
+		System: frame_system,
+		Salary: pallet_salary,
+		Club: pallet_ranked_collective,
+	}
+);
+
+parameter_types! {
+	pub BlockWeights: frame_system::limits::BlockWeights =
+		frame_system::limits::BlockWeights::simple_max(Weight::from_parts(1_000_000, 0));
+}
+
+#[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
+impl frame_system::Config for Test {
+	type Block = Block;
+}
+
+pub struct TestPolls;
+impl Polling<TallyOf<Test>> for TestPolls {
+	type Index = u8;
+	type Votes = Votes;
+	type Moment = u64;
+	type Class = Rank;
+
+	fn classes() -> Vec<Self::Class> {
+		unimplemented!()
+	}
+	fn as_ongoing(_index: u8) -> Option<(TallyOf<Test>, Self::Class)> {
+		unimplemented!()
+	}
+	fn access_poll<R>(
+		_index: Self::Index,
+		_f: impl FnOnce(PollStatus<&mut TallyOf<Test>, Self::Moment, Self::Class>) -> R,
+	) -> R {
+		unimplemented!()
+	}
+	fn try_access_poll<R>(
+		_index: Self::Index,
+		_f: impl FnOnce(
+			PollStatus<&mut TallyOf<Test>, Self::Moment, Self::Class>,
+		) -> Result<R, DispatchError>,
+	) -> Result<R, DispatchError> {
+		unimplemented!()
+	}
+
+	#[cfg(feature = "runtime-benchmarks")]
+	fn create_ongoing(_class: Self::Class) -> Result<Self::Index, ()> {
+		unimplemented!()
+	}
+
+	#[cfg(feature = "runtime-benchmarks")]
+	fn end_ongoing(_index: Self::Index, _approved: bool) -> Result<(), ()> {
+		unimplemented!()
+	}
+}
+
+pub struct MinRankOfClass<Delta>(PhantomData<Delta>);
+impl<Delta: Get<Rank>> Convert<u16, Rank> for MinRankOfClass<Delta> {
+	fn convert(a: u16) -> Rank {
+		a.saturating_sub(Delta::get())
+	}
+}
+
+pub struct TestPay;
+impl Pay for TestPay {
+	type Beneficiary = u64;
+	type Balance = u64;
+	type Id = u64;
+	type AssetKind = ();
+	type Error = ();
+
+	fn pay(
+		_: &Self::Beneficiary,
+		_: Self::AssetKind,
+		_: Self::Balance,
+	) -> Result<Self::Id, Self::Error> {
+		unreachable!()
+	}
+	fn check_payment(_: Self::Id) -> PaymentStatus {
+		unreachable!()
+	}
+	#[cfg(feature = "runtime-benchmarks")]
+	fn ensure_successful(_: &Self::Beneficiary, _: Self::AssetKind, _: Self::Balance) {}
+	#[cfg(feature = "runtime-benchmarks")]
+	fn ensure_concluded(_: Self::Id) {
+		unreachable!()
+	}
+}
+
+parameter_types! {
+	pub static Budget: u64 = 10;
+}
+
+impl Config for Test {
+	type WeightInfo = ();
+	type RuntimeEvent = RuntimeEvent;
+	type Paymaster = TestPay;
+	type Members = Club;
+	type Salary = FixedSalary;
+	type RegistrationPeriod = ConstU64<2>;
+	type PayoutPeriod = ConstU64<2>;
+	type Budget = Budget;
+}
+
+pub struct FixedSalary;
+impl GetSalary<u16, u64, u64> for FixedSalary {
+	fn get_salary(_rank: u16, _who: &u64) -> u64 {
+		123
+	}
+}
+
+parameter_types! {
+	pub static MinRankOfClassDelta: Rank = 0;
+}
+
+impl pallet_ranked_collective::Config for Test {
+	type WeightInfo = ();
+	type RuntimeEvent = RuntimeEvent;
+	type PromoteOrigin = EitherOf<
+		// Root can promote arbitrarily.
+		frame_system::EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>,
+		// Members can promote up to the rank of 2 below them.
+		MapSuccess<EnsureRanked<Test, (), 2>, ReduceBy<ConstU16<2>>>,
+	>;
+	type DemoteOrigin = EitherOf<
+		// Root can demote arbitrarily.
+		frame_system::EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>,
+		// Members can demote up to the rank of 3 below them.
+		MapSuccess<EnsureRanked<Test, (), 3>, ReduceBy<ConstU16<3>>>,
+	>;
+	type ExchangeOrigin = EitherOf<
+		// Root can exchange arbitrarily.
+		frame_system::EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>,
+		// Members can exchange up to the rank of 2 below them.
+		MapSuccess<EnsureRanked<Test, (), 2>, ReduceBy<ConstU16<2>>>,
+	>;
+	type Polls = TestPolls;
+	type MinRankOfClass = MinRankOfClass<MinRankOfClassDelta>;
+	type MemberSwappedHandler = Salary;
+	type VoteWeight = Geometric;
+	#[cfg(feature = "runtime-benchmarks")]
+	type BenchmarkSetup = Salary;
+}
+
+pub fn new_test_ext() -> sp_io::TestExternalities {
+	let t = frame_system::GenesisConfig::<Test>::default().build_storage().unwrap();
+	let mut ext = sp_io::TestExternalities::new(t);
+	ext.execute_with(|| System::set_block_number(1));
+	ext
+}
+
+fn assert_last_event(generic_event: <Test as Config>::RuntimeEvent) {
+	let events = frame_system::Pallet::<Test>::events();
+	let system_event: <Test as frame_system::Config>::RuntimeEvent = generic_event.into();
+	let frame_system::EventRecord { event, .. } = events.last().expect("Event expected");
+	assert_eq!(event, &system_event.into());
+}
+
+fn promote_n_times(acc: u64, r: u16) {
+	for _ in 0..r {
+		assert_ok!(Club::promote_member(RuntimeOrigin::root(), acc));
+	}
+}
+
+#[test]
+fn swap_simple_works() {
+	new_test_ext().execute_with(|| {
+		for i in 0u16..9 {
+			let acc = i as u64;
+
+			assert_ok!(Club::add_member(RuntimeOrigin::root(), acc));
+			promote_n_times(acc, i);
+			let _ = Salary::init(RuntimeOrigin::signed(acc));
+			assert_ok!(Salary::induct(RuntimeOrigin::signed(acc)));
+
+			// Swapping normally works:
+			assert_ok!(Club::exchange_member(RuntimeOrigin::root(), acc, acc + 10));
+			assert_last_event(Event::Swapped { who: acc, new_who: acc + 10 }.into());
+		}
+	});
+}
+
+#[test]
+fn swap_exhaustive_works() {
+	new_test_ext().execute_with(|| {
+		let root_add = hypothetically!({
+			assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
+			assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
+			assert_ok!(Salary::init(RuntimeOrigin::signed(1)));
+			assert_ok!(Salary::induct(RuntimeOrigin::signed(1)));
+
+			// The events mess up the storage root:
+			System::reset_events();
+			sp_io::storage::root(sp_runtime::StateVersion::V1)
+		});
+
+		let root_swap = hypothetically!({
+			assert_ok!(Club::add_member(RuntimeOrigin::root(), 0));
+			assert_ok!(Club::promote_member(RuntimeOrigin::root(), 0));
+			assert_ok!(Salary::init(RuntimeOrigin::signed(0)));
+			assert_ok!(Salary::induct(RuntimeOrigin::signed(0)));
+
+			assert_ok!(Club::exchange_member(RuntimeOrigin::root(), 0, 1));
+
+			// The events mess up the storage root:
+			System::reset_events();
+			sp_io::storage::root(sp_runtime::StateVersion::V1)
+		});
+
+		assert_eq!(root_add, root_swap);
+		// Ensure that we dont compare trivial stuff like `()` from a type error above.
+		assert_eq!(root_add.len(), 32);
+	});
+}
+
+#[test]
+fn swap_bad_noops() {
+	new_test_ext().execute_with(|| {
+		assert_ok!(Club::add_member(RuntimeOrigin::root(), 0));
+		promote_n_times(0, 0);
+		assert_ok!(Salary::init(RuntimeOrigin::signed(0)));
+		assert_ok!(Salary::induct(RuntimeOrigin::signed(0)));
+		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
+		promote_n_times(1, 1);
+		assert_ok!(Salary::induct(RuntimeOrigin::signed(1)));
+
+		// Swapping for another member is a noop:
+		assert_noop!(
+			Club::exchange_member(RuntimeOrigin::root(), 0, 1),
+			pallet_ranked_collective::Error::<Test>::AlreadyMember
+		);
+		// Swapping for the same member is a noop:
+		assert_noop!(
+			Club::exchange_member(RuntimeOrigin::root(), 0, 0),
+			pallet_ranked_collective::Error::<Test>::SameMember
+		);
+	});
+}

substrate/frame/salary/src/tests/mod.rs

@@ -0,0 +1,23 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#![cfg(test)]
+
+//! Unit and integration tests for the salary pallet.
+
+pub(crate) mod integration;
+pub(crate) mod unit;

substrate/frame/salary/src/tests/unit.rs

@@ -23,17 +23,13 @@ use frame_support::{
 	assert_noop, assert_ok, derive_impl,
 	pallet_prelude::Weight,
 	parameter_types,
-	traits::{tokens::ConvertRank, ConstU32, ConstU64, Everything},
-};
-use sp_core::H256;
-use sp_runtime::{
-	traits::{BlakeTwo256, Identity, IdentityLookup},
-	BuildStorage, DispatchResult,
+	traits::{tokens::ConvertRank, ConstU64},
 };
+use sp_runtime::{traits::Identity, BuildStorage, DispatchResult};
 use sp_std::cell::RefCell;
 
-use super::*;
 use crate as pallet_salary;
+use crate::*;
 
 type Block = frame_system::mocking::MockBlock<Test>;
 
@@ -52,29 +48,7 @@ parameter_types! {
 
 #[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
 impl frame_system::Config for Test {
-	type BaseCallFilter = Everything;
-	type BlockWeights = ();
-	type BlockLength = ();
-	type DbWeight = ();
-	type RuntimeOrigin = RuntimeOrigin;
-	type Nonce = u64;
-	type RuntimeCall = RuntimeCall;
-	type Hash = H256;
-	type Hashing = BlakeTwo256;
-	type AccountId = u64;
-	type Lookup = IdentityLookup<Self::AccountId>;
 	type Block = Block;
-	type RuntimeEvent = RuntimeEvent;
-	type BlockHashCount = ConstU64<250>;
-	type Version = ();
-	type PalletInfo = PalletInfo;
-	type AccountData = ();
-	type OnNewAccount = ();
-	type OnKilledAccount = ();
-	type SystemWeightInfo = ();
-	type SS58Prefix = ();
-	type OnSetCode = ();
-	type MaxConsumers = ConstU32<16>;
 }
 
 thread_local! {

substrate/frame/support/src/traits.rs

@@ -37,7 +37,7 @@ pub use members::{AllowAll, DenyAll, Filter};
 pub use members::{
 	AsContains, ChangeMembers, Contains, ContainsLengthBound, ContainsPair, Equals, Everything,
 	EverythingBut, FromContainsPair, InitializeMembers, InsideBoth, IsInVec, Nothing,
-	RankedMembers, SortedMembers, TheseExcept,
+	RankedMembers, RankedMembersSwapHandler, SortedMembers, TheseExcept,
 };
 
 mod validation;

substrate/frame/support/src/traits/dispatch.rs

@@ -490,7 +490,7 @@ pub trait OriginTrait: Sized {
 	/// Add a filter to the origin.
 	fn add_filter(&mut self, filter: impl Fn(&Self::Call) -> bool + 'static);
 
-	/// Reset origin filters to default one, i.e `frame_system::Config::BaseCallFilter`.
+	/// Reset origin filters to default one, i.e `frame_system::1fig::BaseCallFilter`.
 	fn reset_filter(&mut self);
 
 	/// Replace the caller with caller from the other origin

substrate/frame/support/src/traits/members.rs

@@ -297,6 +297,13 @@ pub trait RankedMembers {
 	fn demote(who: &Self::AccountId) -> DispatchResult;
 }
 
+/// Handler that can deal with the swap of two members.
+#[impl_trait_for_tuples::impl_for_tuples(16)]
+pub trait RankedMembersSwapHandler<AccountId, Rank> {
+	/// Member `old` was swapped with `new` at `rank`.
+	fn swapped(who: &AccountId, new_who: &AccountId, rank: Rank);
+}
+
 /// Trait for type that can handle the initialization of account IDs at genesis.
 pub trait InitializeMembers<AccountId> {
 	/// Initialize the members to the given `members`.