Add TransactionFeePaid event (#2218)

* add TransactionFeePaid event

* more event test

* fix comment

modules/transaction-payment/src/lib.rs

@@ -392,6 +392,15 @@ pub mod module {
 			foreign_amount: Balance,
 			native_amount: Balance,
 		},
+		/// A transaction `actual_fee`, of which `actual_tip` was added to the minimum inclusion
+		/// fee, has been paid by `who`. `actual_surplus` indicate extra amount when paid by none
+		/// native token.
+		TransactionFeePaid {
+			who: T::AccountId,
+			actual_fee: PalletBalanceOf<T>,
+			actual_tip: PalletBalanceOf<T>,
+			actual_surplus: PalletBalanceOf<T>,
+		},
 	}
 
 	/// The next fee multiplier.
@@ -1134,7 +1143,7 @@ where
 		(
 			PalletBalanceOf<T>,
 			Option<NegativeImbalanceOf<T>>,
-			Option<PalletBalanceOf<T>>,
+			PalletBalanceOf<T>,
 			T::AccountId,
 		),
 		TransactionValidityError,
@@ -1144,7 +1153,7 @@ where
 
 		// Only mess with balances if fee is not zero.
 		if fee.is_zero() {
-			return Ok((fee, None, None, who.clone()));
+			return Ok((fee, None, 0, who.clone()));
 		}
 
 		let reason = if tip.is_zero() {
@@ -1158,7 +1167,7 @@ where
 
 		// withdraw native currency as fee, also consider surplus when swap from dex or pool.
 		match <T as Config>::Currency::withdraw(&payer, fee + fee_surplus, reason, ExistenceRequirement::KeepAlive) {
-			Ok(imbalance) => Ok((fee + fee_surplus, Some(imbalance), Some(fee_surplus), payer)),
+			Ok(imbalance) => Ok((fee + fee_surplus, Some(imbalance), fee_surplus, payer)),
 			Err(_) => Err(InvalidTransaction::Payment.into()),
 		}
 	}
@@ -1255,8 +1264,8 @@ where
 		PalletBalanceOf<T>,
 		Self::AccountId,
 		Option<NegativeImbalanceOf<T>>,
-		PalletBalanceOf<T>,         // fee includes surplus
-		Option<PalletBalanceOf<T>>, // surplus
+		PalletBalanceOf<T>, // fee includes surplus
+		PalletBalanceOf<T>, // surplus
 	);
 
 	fn additional_signed(&self) -> sp_std::result::Result<(), TransactionValidityError> {
@@ -1312,11 +1321,10 @@ where
 				actual_tip = tip.saturating_sub(refund_tip);
 			}
 			// the refund surplus also need to return back to user
-			if let Some(surplus) = surplus {
-				let percent = Percent::from_rational(surplus, fee.saturating_sub(surplus));
-				let actual_surplus = percent.mul_ceil(actual_fee);
-				refund = refund.saturating_sub(actual_surplus);
-			}
+			let percent = Percent::from_rational(surplus, fee.saturating_sub(surplus));
+			let actual_surplus = percent.mul_ceil(actual_fee);
+			refund = refund.saturating_sub(actual_surplus);
+
 			let actual_payment = match <T as Config>::Currency::deposit_into_existing(&who, refund) {
 				Ok(refund_imbalance) => {
 					// The refund cannot be larger than the up front payed max weight.
@@ -1335,6 +1343,13 @@ where
 
 			// distribute fee
 			<T as Config>::OnTransactionPayment::on_unbalanceds(Some(fee).into_iter().chain(Some(tip)));
+
+			Pallet::<T>::deposit_event(Event::<T>::TransactionFeePaid {
+				who,
+				actual_fee,
+				actual_tip,
+				actual_surplus,
+			});
 		}
 		Ok(())
 	}

modules/transaction-payment/src/tests.rs

@@ -303,6 +303,15 @@ fn pre_post_dispatch_and_refund_native_is_enough() {
 		assert_eq!(FEE_UNBALANCED_AMOUNT.with(|a| *a.borrow()), fee - refund);
 		assert_eq!(TIP_UNBALANCED_AMOUNT.with(|a| *a.borrow()), 0);
 
+		System::assert_has_event(crate::mock::Event::TransactionPayment(
+			crate::Event::TransactionFeePaid {
+				who: ALICE,
+				actual_fee,
+				actual_tip: 0,
+				actual_surplus: 0,
+			},
+		));
+
 		// reset and test refund with tip
 		FEE_UNBALANCED_AMOUNT.with(|a| *a.borrow_mut() = 0);
 
@@ -323,6 +332,15 @@ fn pre_post_dispatch_and_refund_native_is_enough() {
 		assert_eq!(Currencies::free_balance(ACA, &CHARLIE), 100000 - fee - tip + refund);
 		assert_eq!(FEE_UNBALANCED_AMOUNT.with(|a| *a.borrow()), fee - refund);
 		assert_eq!(TIP_UNBALANCED_AMOUNT.with(|a| *a.borrow()), tip);
+
+		System::assert_has_event(crate::mock::Event::TransactionPayment(
+			crate::Event::TransactionFeePaid {
+				who: CHARLIE,
+				actual_fee,
+				actual_tip: tip,
+				actual_surplus: 0,
+			},
+		));
 	});
 }
 
@@ -363,16 +381,26 @@ fn pre_post_dispatch_and_refund_with_fee_path_call() {
 
 		let refund = 200; // 1000 - 800
 		let refund_surplus = 100;
+		let actual_surplus = surplus - refund_surplus;
 		assert_eq!(
 			Currencies::free_balance(ACA, &ALICE),
 			aca_init + refund + refund_surplus
 		);
 		assert_eq!(
 			FEE_UNBALANCED_AMOUNT.with(|a| *a.borrow()),
-			fee - refund + surplus - refund_surplus
+			fee - refund + actual_surplus
 		);
 		assert_eq!(TIP_UNBALANCED_AMOUNT.with(|a| *a.borrow()), 0);
 
+		System::assert_has_event(crate::mock::Event::TransactionPayment(
+			crate::Event::TransactionFeePaid {
+				who: ALICE,
+				actual_fee,
+				actual_tip: 0,
+				actual_surplus,
+			},
+		));
+
 		// reset and test refund with tip
 		FEE_UNBALANCED_AMOUNT.with(|a| *a.borrow_mut() = 0);
 
@@ -418,6 +446,15 @@ fn pre_post_dispatch_and_refund_with_fee_path_call() {
 			fee - refund + surplus - refund_surplus
 		);
 		assert_eq!(TIP_UNBALANCED_AMOUNT.with(|a| *a.borrow()), tip);
+
+		System::assert_has_event(crate::mock::Event::TransactionPayment(
+			crate::Event::TransactionFeePaid {
+				who: CHARLIE,
+				actual_fee,
+				actual_tip: tip,
+				actual_surplus: surplus - refund_surplus,
+			},
+		));
 	});
 }
 
@@ -444,6 +481,15 @@ fn refund_fee_according_to_actual_when_post_dispatch_and_native_currency_is_enou
 		let refund = 200; // 1000 - 800
 		assert!(ChargeTransactionPayment::<Runtime>::post_dispatch(Some(pre), &INFO, &POST_INFO, 23, &Ok(())).is_ok());
 		assert_eq!(Currencies::free_balance(ACA, &ALICE), 100000 - fee + refund);
+
+		System::assert_has_event(crate::mock::Event::TransactionPayment(
+			crate::Event::TransactionFeePaid {
+				who: ALICE,
+				actual_fee: fee - refund,
+				actual_tip: 0,
+				actual_surplus: 0,
+			},
+		));
 	});
 }
 
@@ -461,6 +507,15 @@ fn refund_tip_according_to_actual_when_post_dispatch_and_native_currency_is_enou
 		assert!(ChargeTransactionPayment::<Runtime>::post_dispatch(Some(pre), &INFO, &POST_INFO, 23, &Ok(())).is_ok());
 		assert_eq!(Currencies::free_balance(ACA, &ALICE), 100000 - fee + refund);
 
+		System::assert_has_event(crate::mock::Event::TransactionPayment(
+			crate::Event::TransactionFeePaid {
+				who: ALICE,
+				actual_fee: fee - refund,
+				actual_tip: 0,
+				actual_surplus: 0,
+			},
+		));
+
 		// tip = 1000
 		let fee = 23 * 2 + 1000; // len * byte + weight
 		let tip = 1000;
@@ -476,6 +531,15 @@ fn refund_tip_according_to_actual_when_post_dispatch_and_native_currency_is_enou
 			Currencies::free_balance(ACA, &CHARLIE),
 			100000 - fee - tip + refund_fee + refund_tip
 		);
+
+		System::assert_has_event(crate::mock::Event::TransactionPayment(
+			crate::Event::TransactionFeePaid {
+				who: CHARLIE,
+				actual_fee: fee - refund_fee + tip,
+				actual_tip: tip - refund_tip,
+				actual_surplus: 0,
+			},
+		));
 	});
 }
 
@@ -497,6 +561,15 @@ fn refund_should_not_works() {
 
 		assert!(ChargeTransactionPayment::<Runtime>::post_dispatch(Some(pre), &INFO, &POST_INFO, 23, &Ok(())).is_ok());
 		assert_eq!(Currencies::free_balance(ACA, &ALICE), 100000 - fee - tip);
+
+		System::assert_has_event(crate::mock::Event::TransactionPayment(
+			crate::Event::TransactionFeePaid {
+				who: ALICE,
+				actual_fee: fee + tip,
+				actual_tip: tip,
+				actual_surplus: 0,
+			},
+		));
 	});
 }