diff --git a/prdoc/pr_6592.prdoc b/prdoc/pr_6592.prdoc
new file mode 100644
index 0000000000000000000000000000000000000000..3be9f0fffa2276a26050519937d127ea48a1c3ca
--- /dev/null
+++ b/prdoc/pr_6592.prdoc
@@ -0,0 +1,16 @@
+# 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: Only allow apply slash to be executed if the slash amount is atleast ED
+
+doc:
+ - audience: Runtime User
+ description: |
+ This change prevents `pools::apply_slash` from being executed when the pending slash amount of the member is lower
+ than the ED. With this change, such small slashes will still be applied but only when member funds are withdrawn.
+
+crates:
+- name: pallet-nomination-pools-runtime-api
+ bump: patch
+- name: pallet-nomination-pools
+ bump: patch
diff --git a/substrate/frame/nomination-pools/runtime-api/src/lib.rs b/substrate/frame/nomination-pools/runtime-api/src/lib.rs
index d81ad1dd4954e003680d5e467e5796526bc3edf0..f81856938fecb9d2007afabe96ae3dcbf9db5ed7 100644
--- a/substrate/frame/nomination-pools/runtime-api/src/lib.rs
+++ b/substrate/frame/nomination-pools/runtime-api/src/lib.rs
@@ -43,6 +43,9 @@ sp_api::decl_runtime_apis! {
fn pool_pending_slash(pool_id: PoolId) -> Balance;
/// Returns the pending slash for a given pool member.
+ ///
+ /// If pending slash of the member exceeds `ExistentialDeposit`, it can be reported on
+ /// chain.
fn member_pending_slash(member: AccountId) -> Balance;
/// Returns true if the pool with `pool_id` needs migration.
diff --git a/substrate/frame/nomination-pools/src/lib.rs b/substrate/frame/nomination-pools/src/lib.rs
index 177c5da74d4ff63defd576322ed5097c90ef4a28..25e6b2797cce410c8d0a63225d017ad1ef1b1bf9 100644
--- a/substrate/frame/nomination-pools/src/lib.rs
+++ b/substrate/frame/nomination-pools/src/lib.rs
@@ -1944,6 +1944,8 @@ pub mod pallet {
NothingToAdjust,
/// No slash pending that can be applied to the member.
NothingToSlash,
+ /// The slash amount is too low to be applied.
+ SlashTooLow,
/// The pool or member delegation has already migrated to delegate stake.
AlreadyMigrated,
/// The pool or member delegation has not migrated yet to delegate stake.
@@ -2300,7 +2302,7 @@ pub mod pallet {
let slash_weight =
// apply slash if any before withdraw.
- match Self::do_apply_slash(&member_account, None) {
+ match Self::do_apply_slash(&member_account, None, false) {
Ok(_) => T::WeightInfo::apply_slash(),
Err(e) => {
let no_pending_slash: DispatchResult = Err(Error::<T>::NothingToSlash.into());
@@ -2974,8 +2976,10 @@ pub mod pallet {
/// Fails unless [`crate::pallet::Config::StakeAdapter`] is of strategy type:
/// [`adapter::StakeStrategyType::Delegate`].
///
- /// This call can be dispatched permissionlessly (i.e. by any account). If the member has
- /// slash to be applied, caller may be rewarded with the part of the slash.
+ /// The pending slash amount of the member must be equal or more than `ExistentialDeposit`.
+ /// This call can be dispatched permissionlessly (i.e. by any account). If the execution
+ /// is successful, fee is refunded and caller may be rewarded with a part of the slash
+ /// based on the [`crate::pallet::Config::StakeAdapter`] configuration.
#[pallet::call_index(23)]
#[pallet::weight(T::WeightInfo::apply_slash())]
pub fn apply_slash(
@@ -2989,7 +2993,7 @@ pub mod pallet {
let who = ensure_signed(origin)?;
let member_account = T::Lookup::lookup(member_account)?;
- Self::do_apply_slash(&member_account, Some(who))?;
+ Self::do_apply_slash(&member_account, Some(who), true)?;
// If successful, refund the fees.
Ok(Pays::No.into())
@@ -3574,15 +3578,21 @@ impl<T: Config> Pallet<T> {
fn do_apply_slash(
member_account: &T::AccountId,
reporter: Option<T::AccountId>,
+ enforce_min_slash: bool,
) -> DispatchResult {
let member = PoolMembers::<T>::get(member_account).ok_or(Error::<T>::PoolMemberNotFound)?;
let pending_slash =
Self::member_pending_slash(Member::from(member_account.clone()), member.clone())?;
- // if nothing to slash, return error.
+ // ensure there is something to slash.
ensure!(!pending_slash.is_zero(), Error::<T>::NothingToSlash);
+ if enforce_min_slash {
+ // ensure slashed amount is at least the minimum balance.
+ ensure!(pending_slash >= T::Currency::minimum_balance(), Error::<T>::SlashTooLow);
+ }
+
T::StakeAdapter::member_slash(
Member::from(member_account.clone()),
Pool::from(Pallet::<T>::generate_bonded_account(member.pool_id)),
@@ -3946,6 +3956,9 @@ impl<T: Config> Pallet<T> {
/// Returns the unapplied slash of a member.
///
/// Pending slash is only applicable with [`adapter::DelegateStake`] strategy.
+ ///
+ /// If pending slash of the member exceeds `ExistentialDeposit`, it can be reported on
+ /// chain via [`Call::apply_slash`].
pub fn api_member_pending_slash(who: T::AccountId) -> BalanceOf<T> {
PoolMembers::<T>::get(who.clone())
.map(|pool_member| {
diff --git a/substrate/frame/nomination-pools/test-delegate-stake/Cargo.toml b/substrate/frame/nomination-pools/test-delegate-stake/Cargo.toml
index 288ffd04c8e0f0751784b045fe6680098d399c93..6e6541e638334e846a5d9694a8982a45e829290c 100644
--- a/substrate/frame/nomination-pools/test-delegate-stake/Cargo.toml
+++ b/substrate/frame/nomination-pools/test-delegate-stake/Cargo.toml
@@ -26,7 +26,7 @@ sp-staking = { default-features = true, path = "../../../primitives/staking" }
sp-core = { default-features = true, path = "../../../primitives/core" }
frame-system = { default-features = true, path = "../../system" }
-frame-support = { default-features = true, path = "../../support" }
+frame-support = { features = ["experimental"], default-features = true, path = "../../support" }
frame-election-provider-support = { default-features = true, path = "../../election-provider-support" }
pallet-timestamp = { default-features = true, path = "../../timestamp" }
diff --git a/substrate/frame/nomination-pools/test-delegate-stake/src/lib.rs b/substrate/frame/nomination-pools/test-delegate-stake/src/lib.rs
index 7fee2a0bdb23dfba40963f6c672109bd47999d43..a500887df9ae1825bf39c8b8fb50473dadd8e047 100644
--- a/substrate/frame/nomination-pools/test-delegate-stake/src/lib.rs
+++ b/substrate/frame/nomination-pools/test-delegate-stake/src/lib.rs
@@ -20,7 +20,7 @@
mod mock;
use frame_support::{
- assert_noop, assert_ok,
+ assert_noop, assert_ok, hypothetically,
traits::{fungible::InspectHold, Currency},
};
use mock::*;
@@ -537,9 +537,9 @@ fn pool_slash_proportional() {
// a typical example where 3 pool members unbond in era 99, 100, and 101, and a slash that
// happened in era 100 should only affect the latter two.
new_test_ext().execute_with(|| {
- ExistentialDeposit::set(1);
+ ExistentialDeposit::set(2);
BondingDuration::set(28);
- assert_eq!(Balances::minimum_balance(), 1);
+ assert_eq!(Balances::minimum_balance(), 2);
assert_eq!(Staking::current_era(), None);
// create the pool, we know this has id 1.
@@ -670,6 +670,34 @@ fn pool_slash_proportional() {
// no pending slash yet.
assert_eq!(Pools::api_pool_pending_slash(1), 0);
+ // and therefore applying slash fails
+ assert_noop!(
+ Pools::apply_slash(RuntimeOrigin::signed(10), 21),
+ PoolsError::<Runtime>::NothingToSlash
+ );
+
+ hypothetically!({
+ // a very small amount is slashed
+ pallet_staking::slashing::do_slash::<Runtime>(
+ &POOL1_BONDED,
+ 3,
+ &mut Default::default(),
+ &mut Default::default(),
+ 100,
+ );
+
+ // ensure correct amount is pending to be slashed
+ assert_eq!(Pools::api_pool_pending_slash(1), 3);
+
+ // 21 has pending slash lower than ED (2)
+ assert_eq!(Pools::api_member_pending_slash(21), 1);
+
+ // slash fails as minimum pending slash amount not met.
+ assert_noop!(
+ Pools::apply_slash(RuntimeOrigin::signed(10), 21),
+ PoolsError::<Runtime>::SlashTooLow
+ );
+ });
pallet_staking::slashing::do_slash::<Runtime>(
&POOL1_BONDED,
@@ -909,6 +937,7 @@ fn pool_slash_non_proportional_bonded_pool_and_chunks() {
);
});
}
+
#[test]
fn pool_migration_e2e() {
new_test_ext().execute_with(|| {