backport minimum weight to fee to master (#5739)

* propose fix fees

* add tests to kusama runtime as well

* better tests

* last change

* last update

* Fix test

* ignore tests again

polkadot/runtime/kusama/Cargo.toml

@@ -98,7 +98,7 @@ xcm-builder = { package = "xcm-builder", path = "../../xcm/xcm-builder", default
 
 [dev-dependencies]
 hex-literal = "0.3.4"
-tiny-keccak = "2.0.2"
+tiny-keccak = { version = "2.0.2", features = ["keccak"] }
 keyring = { package = "sp-keyring", git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-trie = { git = "https://github.com/paritytech/substrate", branch = "master" }
 separator = "0.4.1"

polkadot/runtime/kusama/src/lib.rs

@@ -2171,3 +2171,128 @@ mod tests_fess {
 		assert_eq_error_rate!(deposit, UNITS * 16 / 100, UNITS / 100);
 	}
 }
+
+#[cfg(test)]
+mod multiplier_tests {
+	use super::*;
+	use frame_support::{dispatch::GetDispatchInfo, traits::OnFinalize};
+	use runtime_common::{MinimumMultiplier, TargetBlockFullness};
+	use separator::Separatable;
+	use sp_runtime::traits::Convert;
+
+	fn run_with_system_weight<F>(w: Weight, mut assertions: F)
+	where
+		F: FnMut() -> (),
+	{
+		let mut t: sp_io::TestExternalities = frame_system::GenesisConfig::default()
+			.build_storage::<Runtime>()
+			.unwrap()
+			.into();
+		t.execute_with(|| {
+			System::set_block_consumed_resources(w, 0);
+			assertions()
+		});
+	}
+
+	#[test]
+	fn multiplier_can_grow_from_zero() {
+		let minimum_multiplier = MinimumMultiplier::get();
+		let target = TargetBlockFullness::get() *
+			BlockWeights::get().get(DispatchClass::Normal).max_total.unwrap();
+		// if the min is too small, then this will not change, and we are doomed forever.
+		// the weight is 1/100th bigger than target.
+		run_with_system_weight(target * 101 / 100, || {
+			let next = SlowAdjustingFeeUpdate::<Runtime>::convert(minimum_multiplier);
+			assert!(next > minimum_multiplier, "{:?} !>= {:?}", next, minimum_multiplier);
+		})
+	}
+
+	#[test]
+	#[ignore]
+	fn multiplier_growth_simulator() {
+		// assume the multiplier is initially set to its minimum. We update it with values twice the
+		//target (target is 25%, thus 50%) and we see at which point it reaches 1.
+		let mut multiplier = MinimumMultiplier::get();
+		let block_weight = BlockWeights::get().get(DispatchClass::Normal).max_total.unwrap();
+		let mut blocks = 0;
+		let mut fees_paid = 0;
+
+		let call = frame_system::Call::<Runtime>::fill_block {
+			ratio: Perbill::from_rational(
+				block_weight,
+				BlockWeights::get().get(DispatchClass::Normal).max_total.unwrap(),
+			),
+		};
+		println!("calling {:?}", call);
+		let info = call.get_dispatch_info();
+		// convert to outer call.
+		let call = Call::System(call);
+		let len = call.using_encoded(|e| e.len()) as u32;
+
+		let mut t: sp_io::TestExternalities = frame_system::GenesisConfig::default()
+			.build_storage::<Runtime>()
+			.unwrap()
+			.into();
+		// set the minimum
+		t.execute_with(|| {
+			pallet_transaction_payment::NextFeeMultiplier::<Runtime>::set(MinimumMultiplier::get());
+		});
+
+		while multiplier <= Multiplier::from_u32(1) {
+			t.execute_with(|| {
+				// imagine this tx was called.
+				let fee = TransactionPayment::compute_fee(len, &info, 0);
+				fees_paid += fee;
+
+				// this will update the multiplier.
+				System::set_block_consumed_resources(block_weight, 0);
+				TransactionPayment::on_finalize(1);
+				let next = TransactionPayment::next_fee_multiplier();
+
+				assert!(next > multiplier, "{:?} !>= {:?}", next, multiplier);
+				multiplier = next;
+
+				println!(
+					"block = {} / multiplier {:?} / fee = {:?} / fess so far {:?}",
+					blocks,
+					multiplier,
+					fee.separated_string(),
+					fees_paid.separated_string()
+				);
+			});
+			blocks += 1;
+		}
+	}
+
+	#[test]
+	#[ignore]
+	fn multiplier_cool_down_simulator() {
+		// assume the multiplier is initially set to its minimum. We update it with values twice the
+		//target (target is 25%, thus 50%) and we see at which point it reaches 1.
+		let mut multiplier = Multiplier::from_u32(2);
+		let mut blocks = 0;
+
+		let mut t: sp_io::TestExternalities = frame_system::GenesisConfig::default()
+			.build_storage::<Runtime>()
+			.unwrap()
+			.into();
+		// set the minimum
+		t.execute_with(|| {
+			pallet_transaction_payment::NextFeeMultiplier::<Runtime>::set(multiplier);
+		});
+
+		while multiplier > Multiplier::from_u32(0) {
+			t.execute_with(|| {
+				// this will update the multiplier.
+				TransactionPayment::on_finalize(1);
+				let next = TransactionPayment::next_fee_multiplier();
+
+				assert!(next < multiplier, "{:?} !>= {:?}", next, multiplier);
+				multiplier = next;
+
+				println!("block = {} / multiplier {:?}", blocks, multiplier);
+			});
+			blocks += 1;
+		}
+	}
+}