Estimate call fee

bin/node/runtime/src/lib.rs

@@ -573,6 +573,7 @@ impl pallet_election_provider_multi_phase::BenchmarkingConfig for BenchmarkConfi
 impl pallet_election_provider_multi_phase::Config for Runtime {
 	type Event = Event;
 	type Currency = Balances;
+	type EstimateCallFee = TransactionPayment;
 	type SignedPhase = SignedPhase;
 	type UnsignedPhase = UnsignedPhase;
 	type SolutionImprovementThreshold = SolutionImprovementThreshold;

frame/election-provider-multi-phase/src/lib.rs

@@ -237,7 +237,7 @@ use frame_support::{
 };
 use frame_system::{ensure_none, offchain::SendTransactionTypes};
 use sp_arithmetic::{
-	traits::{CheckedAdd, Zero},
+	traits::{CheckedAdd, Saturating, Zero},
 	UpperOf,
 };
 use sp_npos_elections::{
@@ -555,6 +555,7 @@ pub use pallet::*;
 pub mod pallet {
 	use super::*;
 	use frame_support::pallet_prelude::*;
+	use frame_support::traits::EstimateCallFee;
 	use frame_system::pallet_prelude::*;
 
 	#[pallet::config]
@@ -566,6 +567,9 @@ pub mod pallet {
 		/// Currency type.
 		type Currency: ReservableCurrency<Self::AccountId> + Currency<Self::AccountId>;
 
+		/// Something that can predict the fee of a call. Used to sensibly distribute rewards.
+		type EstimateCallFee: EstimateCallFee<Call<Self>, BalanceOf<Self>>;
+
 		/// Duration of the unsigned phase.
 		#[pallet::constant]
 		type UnsignedPhase: Get<Self::BlockNumber>;
@@ -973,7 +977,13 @@ pub mod pallet {
 
 			// create the submission
 			let deposit = Self::deposit_for(&solution, size);
-			let submission = SignedSubmission { who: who.clone(), deposit, solution };
+			let reward = {
+				let call = Call::submit(solution.clone(), num_signed_submissions);
+				let call_fee = T::EstimateCallFee::estimate_call_fee(&call, None.into());
+				T::SignedRewardBase::get().saturating_add(call_fee)
+			};
+
+			let submission = SignedSubmission { who: who.clone(), deposit, solution, reward };
 
 			// insert the submission if the queue has space or it's better than the weakest
 			// eject the weakest if the queue was full

frame/election-provider-multi-phase/src/mock.rs

@@ -261,7 +261,6 @@ parameter_types! {
 	pub static SignedDepositByte: Balance = 0;
 	pub static SignedDepositWeight: Balance = 0;
 	pub static SignedRewardBase: Balance = 7;
-	pub static SignedRewardMax: Balance = 10;
 	pub static SignedMaxWeight: Weight = BlockWeights::get().max_block;
 	pub static MinerMaxIterations: u32 = 5;
 	pub static MinerTxPriority: u64 = 100;
@@ -356,6 +355,7 @@ impl multi_phase::weights::WeightInfo for DualMockWeightInfo {
 impl crate::Config for Runtime {
 	type Event = Event;
 	type Currency = Balances;
+	type EstimateCallFee = frame_support::traits::ConstU32<8>;
 	type SignedPhase = SignedPhase;
 	type UnsignedPhase = UnsignedPhase;
 	type SolutionImprovementThreshold = SolutionImprovementThreshold;

frame/election-provider-multi-phase/src/signed.rs

@@ -51,6 +51,8 @@ pub struct SignedSubmission<AccountId, Balance: HasCompact, CompactSolution> {
 	pub deposit: Balance,
 	/// The raw solution itself.
 	pub solution: RawSolution<CompactSolution>,
+	/// The reward that should potentially be paid for this solution, if accepted.
+	pub reward: Balance,
 }
 
 impl<AccountId, Balance, CompactSolution> Ord
@@ -351,10 +353,8 @@ impl<T: Config> Pallet<T> {
 		let SolutionOrSnapshotSize { voters, targets } =
 			Self::snapshot_metadata().unwrap_or_default();
 
-		let reward = T::SignedRewardBase::get();
-
 		while let Some(best) = all_submissions.pop_last() {
-			let SignedSubmission { solution, who, deposit } = best;
+			let SignedSubmission { solution, who, deposit, reward } = best;
 			let active_voters = solution.compact.voter_count() as u32;
 			let feasibility_weight = {
 				// defensive only: at the end of signed phase, snapshot will exits.
@@ -567,7 +567,7 @@ mod tests {
 			assert_eq!(balances(&99), (95, 5));
 
 			assert!(MultiPhase::finalize_signed_phase().0);
-			assert_eq!(balances(&99), (100 + 7, 0));
+			assert_eq!(balances(&99), (100 + 7 + 8, 0));
 		})
 	}
 
@@ -616,7 +616,7 @@ mod tests {
 			assert!(MultiPhase::finalize_signed_phase().0);
 
 			// 99 is rewarded.
-			assert_eq!(balances(&99), (100 + 7, 0));
+			assert_eq!(balances(&99), (100 + 7 + 8, 0));
 			// 999 gets everything back.
 			assert_eq!(balances(&999), (100, 0));
 		})
@@ -807,7 +807,7 @@ mod tests {
 			assert!(MultiPhase::finalize_signed_phase().0);
 
 			// 99 is rewarded.
-			assert_eq!(balances(&99), (100 + 7, 0));
+			assert_eq!(balances(&99), (100 + 7 + 8, 0));
 			// 999 is slashed.
 			assert_eq!(balances(&999), (95, 0));
 			// 9999 gets everything back.

frame/support/src/traits.rs

@@ -51,9 +51,9 @@ pub use filter::{
 
 mod misc;
 pub use misc::{
-	Backing, ConstU32, EnsureInherentsAreFirst, ExecuteBlock, ExtrinsicCall, Get, GetBacking,
-	GetDefault, HandleLifetime, IsSubType, IsType, Len, OffchainWorker, OnKilledAccount,
-	OnNewAccount, SameOrOther, Time, TryDrop, UnixTime,
+	Backing, ConstU32, EnsureInherentsAreFirst, EstimateCallFee, ExecuteBlock, ExtrinsicCall, Get,
+	GetBacking, GetDefault, HandleLifetime, IsSubType, IsType, Len, OffchainWorker,
+	OnKilledAccount, OnNewAccount, SameOrOther, Time, TryDrop, UnixTime,
 };
 
 mod stored_map;

frame/support/src/traits/misc.rs

@@ -18,7 +18,6 @@
 //! Smaller traits used in FRAME which don't need their own file.
 
 use crate::dispatch::Parameter;
-use sp_arithmetic::traits::AtLeast32Bit;
 use sp_runtime::{traits::Block as BlockT, DispatchError};
 
 /// Anything that can have a `::len()` method.
@@ -181,7 +180,7 @@ pub trait HandleLifetime<T> {
 impl<T> HandleLifetime<T> for () {}
 
 pub trait Time {
-	type Moment: AtLeast32Bit + Parameter + Default + Copy;
+	type Moment: sp_arithmetic::traits::AtLeast32Bit + Parameter + Default + Copy;
 
 	fn now() -> Self::Moment;
 }
@@ -307,7 +306,7 @@ pub trait OffchainWorker<BlockNumber> {
 	fn offchain_worker(_n: BlockNumber) {}
 }
 
-/// Some amount of backing from a group. The precise defintion of what it means to "back" something
+/// Some amount of backing from a group. The precise definition of what it means to "back" something
 /// is left flexible.
 pub struct Backing {
 	/// The number of members of the group that back some motion.
@@ -358,3 +357,21 @@ where
 		&self.function
 	}
 }
+
+/// Something that can estimate the fee of a (frame-based) call.
+///
+/// Typically, the same pallet that will charge transaction fees will implement this.
+pub trait EstimateCallFee<Call, Balance> {
+	/// Estimate the fee of this call.
+	///
+	/// The dispatch info and the length is deduced from the call. The post info can optionally be
+	/// provided.
+	fn estimate_call_fee(call: &Call, post_info: crate::weights::PostDispatchInfo) -> Balance;
+}
+
+#[cfg(feature = "std")]
+impl<Call, Balance: From<u32>, const T: u32> EstimateCallFee<Call, Balance> for ConstU32<T> {
+	fn estimate_call_fee(_: &Call, _: crate::weights::PostDispatchInfo) -> Balance {
+		T.into()
+	}
+}

frame/transaction-payment/src/lib.rs

@@ -52,7 +52,7 @@ use codec::{Decode, Encode};
 use sp_runtime::{
 	traits::{
 		Convert, DispatchInfoOf, Dispatchable, PostDispatchInfoOf, SaturatedConversion, Saturating,
-		SignedExtension,
+		SignedExtension, Zero,
 	},
 	transaction_validity::{
 		TransactionPriority, TransactionValidity, TransactionValidityError, ValidTransaction,
@@ -63,7 +63,7 @@ use sp_std::prelude::*;
 
 use frame_support::{
 	dispatch::DispatchResult,
-	traits::Get,
+	traits::{EstimateCallFee, Get},
 	weights::{
 		DispatchClass, DispatchInfo, GetDispatchInfo, Pays, PostDispatchInfo, Weight,
 		WeightToFeeCoefficient, WeightToFeePolynomial,
@@ -656,6 +656,19 @@ where
 	}
 }
 
+impl<T: Config, AnyCall: GetDispatchInfo + Encode> EstimateCallFee<AnyCall, BalanceOf<T>>
+	for Pallet<T>
+where
+	BalanceOf<T>: FixedPointOperand,
+	T::Call: Dispatchable<Info = DispatchInfo, PostInfo = PostDispatchInfo>,
+{
+	fn estimate_call_fee(call: &AnyCall, post_info: PostDispatchInfo) -> BalanceOf<T> {
+		let len = call.encoded_size() as u32;
+		let info = call.get_dispatch_info();
+		Self::compute_actual_fee(len, &info, &post_info, Zero::zero())
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;