lib.rs

		let expected = <AccountNonce<T>>::get(who);
		if self.0 < expected {
			return Err(DispatchError::Stale)
		}

		let provides = vec![Encode::encode(&(who, self.0))];
		let requires = if expected < self.0 {
			vec![Encode::encode(&(who, self.0 - One::one()))]
		} else {
			vec![]
		};

		Ok(ValidTransaction {
			priority: info.weight as TransactionPriority,
			requires,
			provides,
			longevity: TransactionLongevity::max_value(),
			propagate: true,
		})
	}
}

/// Check for transaction mortality.
#[derive(Encode, Decode, Clone, Eq, PartialEq)]
pub struct CheckEra<T: Trait + Send + Sync>((Era, rstd::marker::PhantomData<T>));

#[cfg(feature = "std")]
impl<T: Trait + Send + Sync> CheckEra<T> {
	/// utility constructor. Used only in client/factory code.
	pub fn from(era: Era) -> Self {
		Self((era, rstd::marker::PhantomData))
	}
}

#[cfg(feature = "std")]
impl<T: Trait + Send + Sync> rstd::fmt::Debug for CheckEra<T> {
	fn fmt(&self, f: &mut rstd::fmt::Formatter) -> rstd::fmt::Result {
		self.0.fmt(f)
	}
}

impl<T: Trait + Send + Sync> SignedExtension for CheckEra<T> {
	type AccountId = T::AccountId;
	type Call = T::Call;
	type AdditionalSigned = T::Hash;
	type Pre = ();

	fn validate(
		&self,
		_who: &Self::AccountId,
		_call: &Self::Call,
		_info: DispatchInfo,
		_len: usize,
	) -> Result<ValidTransaction, DispatchError> {
		let current_u64 = <Module<T>>::block_number().saturated_into::<u64>();
		let valid_till = (self.0).0.death(current_u64);
		Ok(ValidTransaction {
			longevity: valid_till.saturating_sub(current_u64),
			..Default::default()
		})
	}

	fn additional_signed(&self) -> Result<Self::AdditionalSigned, &'static str> {
		let current_u64 = <Module<T>>::block_number().saturated_into::<u64>();
		let n = (self.0).0.birth(current_u64).saturated_into::<T::BlockNumber>();
		if !<BlockHash<T>>::exists(n) { Err("transaction birth block ancient")? }
		Ok(<Module<T>>::block_hash(n))
	}
}

/// Nonce check and increment to give replay protection for transactions.
#[derive(Encode, Decode, Clone, Eq, PartialEq)]
pub struct CheckGenesis<T: Trait + Send + Sync>(rstd::marker::PhantomData<T>);

#[cfg(feature = "std")]
impl<T: Trait + Send + Sync> rstd::fmt::Debug for CheckGenesis<T> {
	fn fmt(&self, _f: &mut rstd::fmt::Formatter) -> rstd::fmt::Result {
		Ok(())
	}
}

#[cfg(feature = "std")]
impl<T: Trait + Send + Sync> CheckGenesis<T> {
	pub fn new() -> Self {
		Self(std::marker::PhantomData)
	}
}

impl<T: Trait + Send + Sync> SignedExtension for CheckGenesis<T> {
	type AccountId = T::AccountId;
	type Call = <T as Trait>::Call;
	type AdditionalSigned = T::Hash;
	type Pre = ();

	fn additional_signed(&self) -> Result<Self::AdditionalSigned, &'static str> {
		Ok(<Module<T>>::block_hash(T::BlockNumber::zero()))
	}
}

/// Ensure the runtime version registered in the transaction is the same as at present.
#[derive(Encode, Decode, Clone, Eq, PartialEq)]
pub struct CheckVersion<T: Trait + Send + Sync>(rstd::marker::PhantomData<T>);

#[cfg(feature = "std")]
impl<T: Trait + Send + Sync> rstd::fmt::Debug for CheckVersion<T> {
	fn fmt(&self, _f: &mut rstd::fmt::Formatter) -> rstd::fmt::Result {
		Ok(())
	}
}

#[cfg(feature = "std")]
impl<T: Trait + Send + Sync> CheckVersion<T> {
	pub fn new() -> Self {
		Self(std::marker::PhantomData)
	}
}

impl<T: Trait + Send + Sync> SignedExtension for CheckVersion<T> {
	type AccountId = T::AccountId;
	type Call = <T as Trait>::Call;
	type AdditionalSigned = u32;
	type Pre = ();

	fn additional_signed(&self) -> Result<Self::AdditionalSigned, &'static str> {
		Ok(<Module<T>>::runtime_version().spec_version)
	}
}

pub struct ChainContext<T>(::rstd::marker::PhantomData<T>);
impl<T> Default for ChainContext<T> {
	fn default() -> Self {
		ChainContext(::rstd::marker::PhantomData)
	}
}

impl<T: Trait> Lookup for ChainContext<T> {
	type Source = <T::Lookup as StaticLookup>::Source;
	type Target = <T::Lookup as StaticLookup>::Target;
	fn lookup(&self, s: Self::Source) -> rstd::result::Result<Self::Target, &'static str> {
		<T::Lookup as StaticLookup>::lookup(s)
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use runtime_io::with_externalities;
	use primitives::H256;
	use sr_primitives::{traits::{BlakeTwo256, IdentityLookup}, testing::Header};
	use srml_support::{impl_outer_origin, parameter_types};

	impl_outer_origin!{
		pub enum Origin for Test where system = super {}
	}

	#[derive(Clone, Eq, PartialEq)]
	pub struct Test;

	parameter_types! {
		pub const BlockHashCount: u64 = 10;
		pub const MaximumBlockWeight: Weight = 1024;
		pub const AvailableBlockRatio: Perbill = Perbill::from_percent(75);
		pub const MaximumBlockLength: u32 = 1024;
	}

	impl Trait for Test {
		type Origin = Origin;
		type Call = ();
		type Index = u64;
		type BlockNumber = u64;
		type Hash = H256;
		type Hashing = BlakeTwo256;
		type AccountId = u64;
		type Lookup = IdentityLookup<Self::AccountId>;
		type Header = Header;
		type WeightMultiplierUpdate = ();
		type Event = u16;
		type BlockHashCount = BlockHashCount;
		type MaximumBlockWeight = MaximumBlockWeight;
		type AvailableBlockRatio = AvailableBlockRatio;
		type MaximumBlockLength = MaximumBlockLength;
		type Version = ();
	}

	impl From<Event> for u16 {
		fn from(e: Event) -> u16 {
			match e {
				Event::ExtrinsicSuccess => 100,
				Event::ExtrinsicFailed => 101,
			}
		}
	}

	type System = Module<Test>;

	const CALL: &<Test as Trait>::Call = &();

	fn new_test_ext() -> runtime_io::TestExternalities<Blake2Hasher> {
		GenesisConfig::default().build_storage::<Test>().unwrap().into()
	}

	fn normal_weight_limit() -> Weight {
		<Test as Trait>::AvailableBlockRatio::get() * <Test as Trait>::MaximumBlockWeight::get()
	}

	fn normal_length_limit() -> u32 {
		<Test as Trait>::AvailableBlockRatio::get() * <Test as Trait>::MaximumBlockLength::get()
	}

	#[test]
	fn origin_works() {
		let o = Origin::from(RawOrigin::<u64>::Signed(1u64));
		let x: Result<RawOrigin<u64>, Origin> = o.into();
		assert_eq!(x, Ok(RawOrigin::<u64>::Signed(1u64)));
	}

	#[test]
	fn deposit_event_should_work() {
		with_externalities(&mut new_test_ext(), || {
			System::initialize(&1, &[0u8; 32].into(), &[0u8; 32].into(), &Default::default());
			System::note_finished_extrinsics();
			System::deposit_event(1u16);
			System::finalize();
			assert_eq!(
				System::events(),
				vec![
					EventRecord {
						phase: Phase::Finalization,
						event: 1u16,
						topics: vec![],
					}
				]
			);

			System::initialize(&2, &[0u8; 32].into(), &[0u8; 32].into(), &Default::default());
			System::deposit_event(42u16);
			System::note_applied_extrinsic(&Ok(()), 0);
			System::note_applied_extrinsic(&Err(""), 0);
			System::note_finished_extrinsics();
			System::deposit_event(3u16);
			System::finalize();
			assert_eq!(System::events(), vec![
				EventRecord { phase: Phase::ApplyExtrinsic(0), event: 42u16, topics: vec![] },
				EventRecord { phase: Phase::ApplyExtrinsic(0), event: 100u16, topics: vec![] },
				EventRecord { phase: Phase::ApplyExtrinsic(1), event: 101u16, topics: vec![] },
				EventRecord { phase: Phase::Finalization, event: 3u16, topics: vec![] }
			]);
		});
	}

	#[test]
	fn deposit_event_topics() {
		with_externalities(&mut new_test_ext(), || {
			const BLOCK_NUMBER: u64 = 1;

			System::initialize(&BLOCK_NUMBER, &[0u8; 32].into(), &[0u8; 32].into(), &Default::default());
			System::note_finished_extrinsics();

			let topics = vec![
				H256::repeat_byte(1),
				H256::repeat_byte(2),
				H256::repeat_byte(3),
			];

			// We deposit a few events with different sets of topics.
			System::deposit_event_indexed(&topics[0..3], 1u16);
			System::deposit_event_indexed(&topics[0..1], 2u16);
			System::deposit_event_indexed(&topics[1..2], 3u16);

			System::finalize();

			// Check that topics are reflected in the event record.
			assert_eq!(
				System::events(),
				vec![
					EventRecord {
						phase: Phase::Finalization,
						event: 1u16,
						topics: topics[0..3].to_vec(),
					},
					EventRecord {
						phase: Phase::Finalization,
						event: 2u16,
						topics: topics[0..1].to_vec(),
					},
					EventRecord {
						phase: Phase::Finalization,
						event: 3u16,
						topics: topics[1..2].to_vec(),
					}
				]
			);

			// Check that the topic-events mapping reflects the deposited topics.
			// Note that these are indexes of the events.
			assert_eq!(
				System::event_topics(&(), &topics[0]),
				vec![(BLOCK_NUMBER, 0), (BLOCK_NUMBER, 1)],
			);
			assert_eq!(
				System::event_topics(&(), &topics[1]),
				vec![(BLOCK_NUMBER, 0), (BLOCK_NUMBER, 2)],
			);
			assert_eq!(
				System::event_topics(&(), &topics[2]),
				vec![(BLOCK_NUMBER, 0)],
			);
		});
	}

	#[test]
	fn prunes_block_hash_mappings() {
		with_externalities(&mut new_test_ext(), || {
			// simulate import of 15 blocks
			for n in 1..=15 {
				System::initialize(
					&n,
					&[n as u8 - 1; 32].into(),
					&[0u8; 32].into(),
					&Default::default(),
				);

				System::finalize();
			}

			// first 5 block hashes are pruned
			for n in 0..5 {
				assert_eq!(
					System::block_hash(n),
					H256::zero(),
				);
			}

			// the remaining 10 are kept
			for n in 5..15 {
				assert_eq!(
					System::block_hash(n),
					[n as u8; 32].into(),
				);
			}
		})
	}

	#[test]
	fn signed_ext_check_nonce_works() {
		with_externalities(&mut new_test_ext(), || {
			<AccountNonce<Test>>::insert(1, 1);
			let info = DispatchInfo::default();
			let len = 0_usize;
			// stale
			assert!(CheckNonce::<Test>(0).validate(&1, CALL, info, len).is_err());
			assert!(CheckNonce::<Test>(0).pre_dispatch(&1, CALL, info, len).is_err());
			// correct
			assert!(CheckNonce::<Test>(1).validate(&1, CALL, info, len).is_ok());
			assert!(CheckNonce::<Test>(1).pre_dispatch(&1, CALL, info, len).is_ok());
			// future
			assert!(CheckNonce::<Test>(5).validate(&1, CALL, info, len).is_ok());
			assert!(CheckNonce::<Test>(5).pre_dispatch(&1, CALL, info, len).is_err());
		})
	}

	#[test]
	fn signed_ext_check_weight_works_normal_tx() {
		with_externalities(&mut new_test_ext(), || {
			let normal_limit = normal_weight_limit();
			let small = DispatchInfo { weight: 100, ..Default::default() };
			let medium = DispatchInfo {
				weight: normal_limit - 1,
				..Default::default()
			};
			let big = DispatchInfo {
				weight: normal_limit + 1,
				..Default::default()
			};
			let len = 0_usize;

			let reset_check_weight = |i, f, s| {
				AllExtrinsicsWeight::put(s);
				let r = CheckWeight::<Test>(PhantomData).pre_dispatch(&1, CALL, i, len);
				if f { assert!(r.is_err()) } else { assert!(r.is_ok()) }
			};

			reset_check_weight(small, false, 0);
			reset_check_weight(medium, false, 0);
			reset_check_weight(big, true, 1);
		})
	}

	#[test]
	fn signed_ext_check_weight_fee_works() {
		with_externalities(&mut new_test_ext(), || {
			let free = DispatchInfo { weight: 0, ..Default::default() };
			let len = 0_usize;

			assert_eq!(System::all_extrinsics_weight(), 0);
			let r = CheckWeight::<Test>(PhantomData).pre_dispatch(&1, CALL, free, len);
			assert!(r.is_ok());
			assert_eq!(System::all_extrinsics_weight(), 0);
		})
	}

	#[test]
	fn signed_ext_check_weight_max_works() {
		with_externalities(&mut new_test_ext(), || {
			let max = DispatchInfo { weight: Weight::max_value(), ..Default::default() };
			let len = 0_usize;
			let normal_limit = normal_weight_limit();

			assert_eq!(System::all_extrinsics_weight(), 0);
			let r = CheckWeight::<Test>(PhantomData).pre_dispatch(&1, CALL, max, len);
			assert!(r.is_ok());
			assert_eq!(System::all_extrinsics_weight(), normal_limit);
		})
	}

	#[test]
	fn signed_ext_check_weight_works_operational_tx() {
		with_externalities(&mut new_test_ext(), || {
			let normal = DispatchInfo { weight: 100, ..Default::default() };
			let op = DispatchInfo { weight: 100, class: DispatchClass::Operational };
			let len = 0_usize;
			let normal_limit = normal_weight_limit();

			// given almost full block
			AllExtrinsicsWeight::put(normal_limit);
			// will not fit.
			assert!(CheckWeight::<Test>(PhantomData).pre_dispatch(&1, CALL, normal, len).is_err());
			// will fit.
			assert!(CheckWeight::<Test>(PhantomData).pre_dispatch(&1, CALL, op, len).is_ok());

			// likewise for length limit.
			let len = 100_usize;
			AllExtrinsicsLen::put(normal_length_limit());
			assert!(CheckWeight::<Test>(PhantomData).pre_dispatch(&1, CALL, normal, len).is_err());
			assert!(CheckWeight::<Test>(PhantomData).pre_dispatch(&1, CALL, op, len).is_ok());
		})
	}

	#[test]
	fn signed_ext_check_weight_priority_works() {
		with_externalities(&mut new_test_ext(), || {
			let normal = DispatchInfo { weight: 100, class: DispatchClass::Normal };
			let op = DispatchInfo { weight: 100, class: DispatchClass::Operational };
			let len = 0_usize;

			assert_eq!(
				CheckWeight::<Test>(PhantomData).validate(&1, CALL, normal, len).unwrap().priority,
				100,
			);
			assert_eq!(
				CheckWeight::<Test>(PhantomData).validate(&1, CALL, op, len).unwrap().priority,
				Bounded::max_value(),
			);
		})
	}

	#[test]
	fn signed_ext_check_weight_block_size_works() {
		with_externalities(&mut new_test_ext(), || {
			let normal = DispatchInfo::default();
			let normal_limit = normal_weight_limit() as usize;
			let reset_check_weight = |tx, s, f| {
				AllExtrinsicsLen::put(0);
				let r = CheckWeight::<Test>(PhantomData).pre_dispatch(&1, CALL, tx, s);
				if f { assert!(r.is_err()) } else { assert!(r.is_ok()) }
			};

			reset_check_weight(normal, normal_limit - 1, false);
			reset_check_weight(normal, normal_limit, false);
			reset_check_weight(normal, normal_limit + 1, true);

			// Operational ones don't have this limit.
			let op = DispatchInfo { weight: 0, class: DispatchClass::Operational };
			reset_check_weight(op, normal_limit, false);
			reset_check_weight(op, normal_limit + 100, false);
			reset_check_weight(op, 1024, false);
			reset_check_weight(op, 1025, true);
		})
	}

	#[test]
	fn signed_ext_check_era_should_work() {
		with_externalities(&mut new_test_ext(), || {
			// future
			assert_eq!(
				CheckEra::<Test>::from(Era::mortal(4, 2)).additional_signed().err().unwrap(),
				"transaction birth block ancient"
			);

			// correct
			System::set_block_number(13);
			<BlockHash<Test>>::insert(12, H256::repeat_byte(1));
			assert!(CheckEra::<Test>::from(Era::mortal(4, 12)).additional_signed().is_ok());
		})
	}

	#[test]
	fn signed_ext_check_era_should_change_longevity() {
		with_externalities(&mut new_test_ext(), || {
			let normal = DispatchInfo { weight: 100, class: DispatchClass::Normal };
			let len = 0_usize;
			let ext = (
				CheckWeight::<Test>(PhantomData),
				CheckEra::<Test>::from(Era::mortal(16, 256)),
			);
			System::set_block_number(17);
			<BlockHash<Test>>::insert(16, H256::repeat_byte(1));

			assert_eq!(
				ext.validate(&1, CALL, normal, len).unwrap().longevity,
				15,
			);
		})
	}
}