Transaction Fee Module (#1648)

* wip

* Split bytes fee charging and charging by amount into different traits.

* Move to edition 2018.

* Implemented charge fee traits for fees module.

* Implemented 'on_finalise' for fee module.

* Updated fees finalize impl.

* Renaming and documentation update.

* Added overflow & underflow check for fee calculation.

* Added mock and unit tests for fee module.

* More unit tests for fees module.

* Fixed srml-executive unit tests.

* Remove transaction base/bytes fee from balances module, fix unit tests.

* fix compile error

* Fixed unit test.

* Minor fixes.

* Bump spec version.

* Bump spec version.

* Updated fees module and runtime wasm.

* Fees module code style improvement; updated runtime wasm.

* Bump spec and impl version.

substrate/srml/fees/src/mock.rs

@@ -0,0 +1,109 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Test utilities
+
+#![cfg(test)]
+
+use runtime_primitives::BuildStorage;
+use runtime_primitives::{
+	traits::{IdentityLookup, BlakeTwo256, TransferAsset},
+	testing::{Digest, DigestItem, Header},
+};
+use primitives::{H256, Blake2Hasher};
+use runtime_io;
+use srml_support::{impl_outer_origin, impl_outer_event};
+use crate::{GenesisConfig, Module, Trait, system};
+
+impl_outer_origin!{
+	pub enum Origin for Test {}
+}
+
+mod fees {
+	pub use crate::Event;
+}
+
+impl_outer_event!{
+	pub enum TestEvent for Test {
+		fees<T>,
+	}
+}
+
+pub struct TransferAssetMock;
+
+impl<AccountId> TransferAsset<AccountId> for TransferAssetMock {
+	type Amount = u64;
+
+	fn transfer(_: &AccountId, _: &AccountId, _: Self::Amount) -> Result<(), &'static str> { Ok(()) }
+	fn remove_from(_: &AccountId, _: Self::Amount) -> Result<(), &'static str> { Ok(()) }
+	fn add_to(_: &AccountId, _: Self::Amount) -> Result<(), &'static str> { Ok(()) }
+}
+
+// Workaround for https://github.com/rust-lang/rust/issues/26925 . Remove when sorted.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct Test;
+impl system::Trait for Test {
+	type Origin = Origin;
+	type Index = u64;
+	type BlockNumber = u64;
+	type Hash = H256;
+	type Hashing = BlakeTwo256;
+	type Digest = Digest;
+	type AccountId = u64;
+	type Lookup = IdentityLookup<u64>;
+	type Header = Header;
+	type Event = TestEvent;
+	type Log = DigestItem;
+}
+impl Trait for Test {
+	type Amount = u64;
+	type Event =TestEvent;
+	type TransferAsset = TransferAssetMock;
+}
+
+pub type System = system::Module<Test>;
+pub type Fees = Module<Test>;
+
+pub struct ExtBuilder {
+	transaction_base_fee: u64,
+	transaction_byte_fee: u64,
+}
+impl Default for ExtBuilder {
+	fn default() -> Self {
+		Self {
+			transaction_base_fee: 0,
+			transaction_byte_fee: 0,
+		}
+	}
+}
+impl ExtBuilder {
+	pub fn transaction_base_fee(mut self, transaction_base_fee: u64) -> Self {
+		self.transaction_base_fee = transaction_base_fee;
+		self
+	}
+	pub fn transaction_byte_fee(mut self, transaction_byte_fee: u64) -> Self {
+		self.transaction_byte_fee = transaction_byte_fee;
+		self
+	}
+	pub fn build(self) -> runtime_io::TestExternalities<Blake2Hasher> {
+		let mut t = system::GenesisConfig::<Test>::default().build_storage().unwrap().0;
+		t.extend(GenesisConfig::<Test> {
+			transaction_base_fee: self.transaction_base_fee,
+			transaction_byte_fee: self.transaction_byte_fee,
+		}.build_storage().unwrap().0);
+		t.into()
+	}
+}