Factor out checks for staking's bond & nominate

frame/staking/src/pallet/impls.rs

@@ -32,7 +32,7 @@ use frame_support::{
 use frame_system::pallet_prelude::BlockNumberFor;
 use pallet_session::historical;
 use sp_runtime::{
-	traits::{Bounded, Convert, SaturatedConversion, Saturating, Zero},
+	traits::{Bounded, Convert, SaturatedConversion, Saturating, StaticLookup, Zero},
 	Perbill,
 };
 use sp_staking::{
@@ -848,6 +848,89 @@ impl<T: Config> Pallet<T> {
 			DispatchClass::Mandatory,
 		);
 	}
+
+	/// Checks for [`Self::bond`] that can be completed at the beginning of the calls logic.
+	pub(crate) fn ensure_can_bond(
+		stash: &T::AccountId,
+		controller: &T::AccountId,
+		value: BalanceOf<T>,
+	) -> Result<(), DispatchError> {
+		if Bonded::<T>::contains_key(&stash) {
+			Err(Error::<T>::AlreadyBonded)?
+		}
+
+		if Ledger::<T>::contains_key(&controller) {
+			Err(Error::<T>::AlreadyPaired)?
+		}
+
+		// Reject a bond which is considered to be _dust_.
+		if value < T::Currency::minimum_balance() {
+			Err(Error::<T>::InsufficientBond)?
+		}
+
+		Ok(())
+	}
+
+	/// Checks for [`Self::nominate`] that must be called prior to
+	/// [`Self::do_unchecked_nominate_writes`].
+	pub(crate) fn ensure_can_nominate(
+		controller: &T::AccountId,
+		targets: Vec<<T::Lookup as StaticLookup>::Source>,
+	) -> Result<(T::AccountId, BoundedVec<T::AccountId, T::MaxNominations>), DispatchError> {
+		let ledger = Self::ledger(controller).ok_or(Error::<T>::NotController)?;
+		ensure!(ledger.active >= MinNominatorBond::<T>::get(), Error::<T>::InsufficientBond);
+
+		// Only check limits if they are not already a nominator.
+		if !Nominators::<T>::contains_key(&ledger.stash) {
+			// If this error is reached, we need to adjust the `MinNominatorBond` and start
+			// calling `chill_other`. Until then, we explicitly block new nominators to protect
+			// the runtime.
+			if let Some(max_nominators) = MaxNominatorsCount::<T>::get() {
+				ensure!(Nominators::<T>::count() < max_nominators, Error::<T>::TooManyNominators);
+			}
+		}
+
+		ensure!(!targets.is_empty(), Error::<T>::EmptyTargets);
+		ensure!(targets.len() <= T::MaxNominations::get() as usize, Error::<T>::TooManyTargets);
+
+		let old =
+			Nominators::<T>::get(&ledger.stash).map_or_else(Vec::new, |x| x.targets.into_inner());
+
+		let targets: BoundedVec<_, _> = targets
+			.into_iter()
+			.map(|t| T::Lookup::lookup(t).map_err(DispatchError::from))
+			.map(|n| {
+				n.and_then(|n| {
+					if old.contains(&n) || !Validators::<T>::get(&n).blocked {
+						Ok(n)
+					} else {
+						Err(Error::<T>::BadTarget.into())
+					}
+				})
+			})
+			.collect::<Result<Vec<_>, _>>()?
+			.try_into()
+			.map_err(|_| Error::<T>::TooManyNominators)?;
+
+		Ok((ledger.stash, targets))
+	}
+
+	/// Write the information for nominating. The caller must first call
+	/// [`Self::ensure_can_nominate`].
+	pub(crate) fn do_unchecked_nominate(
+		stash: &T::AccountId,
+		targets: BoundedVec<T::AccountId, T::MaxNominations>,
+	) {
+		let nominations = Nominations {
+			targets,
+			// Initial nominations are considered submitted at era 0. See `Nominations` doc.
+			submitted_in: Self::current_era().unwrap_or(0),
+			suppressed: false,
+		};
+
+		Self::do_remove_validator(&stash);
+		Self::do_add_nominator(&stash, nominations);
+	}
 }
 
 impl<T: Config> ElectionDataProvider for Pallet<T> {

frame/staking/src/pallet/mod.rs

@@ -29,7 +29,7 @@ use frame_support::{
 use frame_system::{ensure_root, ensure_signed, offchain::SendTransactionTypes, pallet_prelude::*};
 use sp_runtime::{
 	traits::{CheckedSub, SaturatedConversion, StaticLookup, Zero},
-	DispatchError, Perbill, Percent,
+	Perbill, Percent,
 };
 use sp_staking::{EraIndex, SessionIndex};
 use sp_std::{convert::From, prelude::*};
@@ -737,21 +737,9 @@ pub mod pallet {
 			payee: RewardDestination<T::AccountId>,
 		) -> DispatchResult {
 			let stash = ensure_signed(origin)?;
-
-			if <Bonded<T>>::contains_key(&stash) {
-				Err(Error::<T>::AlreadyBonded)?
-			}
-
 			let controller = T::Lookup::lookup(controller)?;
 
-			if <Ledger<T>>::contains_key(&controller) {
-				Err(Error::<T>::AlreadyPaired)?
-			}
-
-			// Reject a bond which is considered to be _dust_.
-			if value < T::Currency::minimum_balance() {
-				Err(Error::<T>::InsufficientBond)?
-			}
+			Self::ensure_can_bond(&stash, &controller, value)?;
 
 			frame_system::Pallet::<T>::inc_consumers(&stash).map_err(|_| Error::<T>::BadState)?;
 
@@ -1003,54 +991,8 @@ pub mod pallet {
 			targets: Vec<<T::Lookup as StaticLookup>::Source>,
 		) -> DispatchResult {
 			let controller = ensure_signed(origin)?;
-
-			let ledger = Self::ledger(&controller).ok_or(Error::<T>::NotController)?;
-			ensure!(ledger.active >= MinNominatorBond::<T>::get(), Error::<T>::InsufficientBond);
-			let stash = &ledger.stash;
-
-			// Only check limits if they are not already a nominator.
-			if !Nominators::<T>::contains_key(stash) {
-				// If this error is reached, we need to adjust the `MinNominatorBond` and start
-				// calling `chill_other`. Until then, we explicitly block new nominators to protect
-				// the runtime.
-				if let Some(max_nominators) = MaxNominatorsCount::<T>::get() {
-					ensure!(
-						Nominators::<T>::count() < max_nominators,
-						Error::<T>::TooManyNominators
-					);
-				}
-			}
-
-			ensure!(!targets.is_empty(), Error::<T>::EmptyTargets);
-			ensure!(targets.len() <= T::MaxNominations::get() as usize, Error::<T>::TooManyTargets);
-
-			let old = Nominators::<T>::get(stash).map_or_else(Vec::new, |x| x.targets.into_inner());
-
-			let targets: BoundedVec<_, _> = targets
-				.into_iter()
-				.map(|t| T::Lookup::lookup(t).map_err(DispatchError::from))
-				.map(|n| {
-					n.and_then(|n| {
-						if old.contains(&n) || !Validators::<T>::get(&n).blocked {
-							Ok(n)
-						} else {
-							Err(Error::<T>::BadTarget.into())
-						}
-					})
-				})
-				.collect::<Result<Vec<_>, _>>()?
-				.try_into()
-				.map_err(|_| Error::<T>::TooManyNominators)?;
-
-			let nominations = Nominations {
-				targets,
-				// Initial nominations are considered submitted at era 0. See `Nominations` doc.
-				submitted_in: Self::current_era().unwrap_or(0),
-				suppressed: false,
-			};
-
-			Self::do_remove_validator(stash);
-			Self::do_add_nominator(stash, nominations);
+			let (stash, targets) = Self::ensure_can_nominate(&controller, targets)?;
+			Self::do_unchecked_nominate(&stash, targets);
 			Ok(())
 		}