Make Staking pallet using a proper Time module. (#4662)

* add new trait, still migration to make

* Apply suggestions from code review

Co-Authored-By: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* implement migration

* better naming

* fix test

* no longer require DeprecatedTime

* add test

* fix version

* upgrade only from kusama

* add test

* fix test

* Update frame/timestamp/src/lib.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/Cargo.lock

@@ -4514,6 +4514,7 @@ dependencies = [
  "frame-benchmarking",
  "frame-support",
  "frame-system",
+ "hex",
  "pallet-authorship",
  "pallet-balances",
  "pallet-session",

substrate/bin/node/runtime/src/lib.rs

@@ -283,7 +283,7 @@ parameter_types! {
 
 impl pallet_staking::Trait for Runtime {
 	type Currency = Balances;
-	type Time = Timestamp;
+	type UnixTime = Timestamp;
 	type CurrencyToVote = CurrencyToVoteHandler;
 	type RewardRemainder = Treasury;
 	type Event = Event;

substrate/frame/staking/Cargo.toml

@@ -33,6 +33,7 @@ pallet-staking-reward-curve = { version = "2.0.0-alpha.5",  path = "../staking/r
 substrate-test-utils = { version = "2.0.0-alpha.5", path = "../../test-utils" }
 frame-benchmarking = { version = "2.0.0-alpha.5", path = "../benchmarking" }
 rand_chacha = { version = "0.2" }
+hex = "0.4"
 
 [features]
 default = ["std"]

substrate/frame/staking/src/lib.rs

@@ -262,11 +262,12 @@ pub mod inflation;
 use sp_std::{prelude::*, result, collections::btree_map::BTreeMap};
 use codec::{HasCompact, Encode, Decode};
 use frame_support::{
-	decl_module, decl_event, decl_storage, ensure, decl_error, weights::SimpleDispatchInfo,
+	decl_module, decl_event, decl_storage, ensure, decl_error,
 	dispatch::DispatchResult, storage::IterableStorageMap, traits::{
 		Currency, LockIdentifier, LockableCurrency, WithdrawReasons, OnUnbalanced, Imbalance, Get,
-		Time
+		UnixTime
-	}
+	},
+	weights::{SimpleDispatchInfo, Weight},
 };
 use pallet_session::historical::SessionManager;
 use sp_runtime::{
@@ -300,14 +301,14 @@ pub type RewardPoint = u32;
 
 /// Information regarding the active era (era in used in session).
 #[derive(Encode, Decode, RuntimeDebug)]
-pub struct ActiveEraInfo<Moment> {
+pub struct ActiveEraInfo {
 	/// Index of era.
 	index: EraIndex,
-	/// Moment of start
+	/// Moment of start expresed as millisecond from `$UNIX_EPOCH`.
 	///
 	/// Start can be none if start hasn't been set for the era yet,
 	/// Start is set on the first on_finalize of the era to guarantee usage of `Time`.
-	start: Option<Moment>,
+	start: Option<u64>,
 }
 
 /// Reward points of an era. Used to split era total payout between validators.
@@ -564,7 +565,6 @@ type PositiveImbalanceOf<T> =
 	<<T as Trait>::Currency as Currency<<T as frame_system::Trait>::AccountId>>::PositiveImbalance;
 type NegativeImbalanceOf<T> =
 	<<T as Trait>::Currency as Currency<<T as frame_system::Trait>::AccountId>>::NegativeImbalance;
-type MomentOf<T> = <<T as Trait>::Time as Time>::Moment;
 
 /// Means for interacting with a specialized version of the `session` trait.
 ///
@@ -613,7 +613,7 @@ pub trait Trait: frame_system::Trait {
 	///
 	/// It is guaranteed to start being called from the first `on_finalize`. Thus value at genesis
 	/// is not used.
-	type Time: Time;
+	type UnixTime: UnixTime;
 
 	/// Convert a balance into a number used for election calculation.
 	/// This must fit into a `u64` but is allowed to be sensibly lossy.
@@ -686,11 +686,12 @@ impl Default for Forcing {
 enum Releases {
 	V1_0_0Ancient,
 	V2_0_0,
+	V3_0_0,
 }
 
 impl Default for Releases {
 	fn default() -> Self {
-		Releases::V2_0_0
+		Releases::V3_0_0
 	}
 }
 
@@ -746,7 +747,7 @@ decl_storage! {
 		///
 		/// The active era is the era currently rewarded.
 		/// Validator set of this era must be equal to `SessionInterface::validators`.
-		pub ActiveEra get(fn active_era): Option<ActiveEraInfo<MomentOf<T>>>;
+		pub ActiveEra get(fn active_era): Option<ActiveEraInfo>;
 
 		/// The session index at which the era start for the last `HISTORY_DEPTH` eras
 		pub ErasStartSessionIndex get(fn eras_start_session_index):
@@ -850,8 +851,8 @@ decl_storage! {
 
 		/// Storage version of the pallet.
 		///
-		/// This is set to v2.0.0 for new networks.
+		/// This is set to v3.0.0 for new networks.
-		StorageVersion build(|_: &GenesisConfig<T>| Releases::V2_0_0): Releases;
+		StorageVersion build(|_: &GenesisConfig<T>| Releases::V3_0_0): Releases;
 	}
 	add_extra_genesis {
 		config(stakers):
@@ -959,12 +960,20 @@ decl_module! {
 			// Set the start of the first era.
 			if let Some(mut active_era) = Self::active_era() {
 				if active_era.start.is_none() {
-					active_era.start = Some(T::Time::now());
+					let now_as_millis_u64 = T::UnixTime::now().as_millis().saturated_into::<u64>();
-					<ActiveEra<T>>::put(active_era);
+					active_era.start = Some(now_as_millis_u64);
+					ActiveEra::put(active_era);
 				}
 			}
 		}
 
+		fn on_runtime_upgrade() -> Weight {
+			// For Kusama the type hasn't actually changed as Moment was u64 and was the number of
+			// millisecond since unix epoch.
+			StorageVersion::put(Releases::V3_0_0);
+			0
+		}
+
 		/// Take the origin account as a stash and lock up `value` of its balance. `controller` will
 		/// be the account that controls it.
 		///
@@ -1696,7 +1705,7 @@ impl<T: Trait> Module<T> {
 	/// * reset `active_era.start`,
 	/// * update `BondedEras` and apply slashes.
 	fn start_era(start_session: SessionIndex) {
-		let active_era = <ActiveEra<T>>::mutate(|active_era| {
+		let active_era = ActiveEra::mutate(|active_era| {
 			let new_index = active_era.as_ref().map(|info| info.index + 1).unwrap_or(0);
 			*active_era = Some(ActiveEraInfo {
 				index: new_index,
@@ -1734,12 +1743,12 @@ impl<T: Trait> Module<T> {
 	}
 
 	/// Compute payout for era.
-	fn end_era(active_era: ActiveEraInfo<MomentOf<T>>, _session_index: SessionIndex) {
+	fn end_era(active_era: ActiveEraInfo, _session_index: SessionIndex) {
 		// Note: active_era_start can be None if end era is called during genesis config.
 		if let Some(active_era_start) = active_era.start {
-			let now = T::Time::now();
+			let now_as_millis_u64 = T::UnixTime::now().as_millis().saturated_into::<u64>();
 
-			let era_duration = now - active_era_start;
+			let era_duration = now_as_millis_u64 - active_era_start;
 			let (total_payout, _max_payout) = inflation::compute_total_payout(
 				&T::RewardCurve::get(),
 				Self::eras_total_stake(&active_era.index),

substrate/frame/staking/src/mock.rs

@@ -201,8 +201,8 @@ parameter_types! {
 	pub const MaxNominatorRewardedPerValidator: u32 = 64;
 }
 impl Trait for Test {
-	type Currency = pallet_balances::Module<Self>;
+	type Currency = Balances;
-	type Time = pallet_timestamp::Module<Self>;
+	type UnixTime = Timestamp;
 	type CurrencyToVote = CurrencyToVoteHandler;
 	type RewardRemainder = ();
 	type Event = ();

substrate/frame/staking/src/tests.rs

@@ -21,9 +21,8 @@ use mock::*;
 use sp_runtime::{assert_eq_error_rate, traits::BadOrigin};
 use sp_staking::offence::OffenceDetails;
 use frame_support::{
-	assert_ok, assert_noop,
+	assert_ok, assert_noop, StorageMap,
 	traits::{Currency, ReservableCurrency, OnInitialize},
-	StorageMap,
 };
 use pallet_balances::Error as BalancesError;
 use substrate_test_utils::assert_eq_uvec;
@@ -3039,3 +3038,11 @@ fn set_history_depth_works() {
 		assert!(!<Staking as Store>::ErasTotalStake::contains_key(10 - 5));
 	});
 }
+
+#[test]
+fn assert_migration_is_noop() {
+	let kusama_active_era = "4a0200000190e2721171010000";
+	let era = ActiveEraInfo::decode(&mut &hex::decode(kusama_active_era).unwrap()[..]).unwrap();
+	assert_eq!(era.index, 586);
+	assert_eq!(era.start, Some(1585135674000));
+}

substrate/frame/support/src/traits.rs

@@ -858,6 +858,12 @@ pub trait Time {
 	fn now() -> Self::Moment;
 }
 
+/// Trait to deal with unix time.
+pub trait UnixTime {
+	/// Return duration since `SystemTime::UNIX_EPOCH`.
+	fn now() -> core::time::Duration;
+}
+
 impl WithdrawReasons {
 	/// Choose all variants except for `one`.
 	///

substrate/frame/timestamp/src/lib.rs

@@ -95,15 +95,17 @@ mod benchmarking;
 
 use sp_std::{result, cmp};
 use sp_inherents::{ProvideInherent, InherentData, InherentIdentifier};
-use frame_support::{Parameter, decl_storage, decl_module};
+use frame_support::{
-use frame_support::traits::{Time, Get};
+	Parameter, decl_storage, decl_module, debug,
+	traits::{Time, UnixTime, Get},
+	weights::SimpleDispatchInfo,
+};
 use sp_runtime::{
 	RuntimeString,
 	traits::{
 		AtLeast32Bit, Zero, SaturatedConversion, Scale
 	}
 };
-use frame_support::weights::SimpleDispatchInfo;
 use frame_system::ensure_none;
 use sp_timestamp::{
 	InherentError, INHERENT_IDENTIFIER, InherentType,
@@ -239,6 +241,25 @@ impl<T: Trait> Time for Module<T> {
 	}
 }
 
+/// Before the timestamp inherent is applied, it returns the time of previous block.
+///
+/// On genesis the time returned is not valid.
+impl<T: Trait> UnixTime for Module<T> {
+	fn now() -> core::time::Duration {
+		// now is duration since unix epoch in millisecond as documented in
+		// `sp_timestamp::InherentDataProvider`.
+		let now = Self::now();
+		sp_std::if_std! { 
+			if now == T::Moment::zero() {
+				debug::error!(
+					"`pallet_timestamp::UnixTime::now` is called at genesis, invalid value returned: 0"
+				);
+			}
+		}
+		core::time::Duration::from_millis(now.saturated_into::<u64>())
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;

substrate/primitives/timestamp/src/lib.rs

@@ -77,6 +77,7 @@ impl TimestampInherentData for InherentData {
 	}
 }
 
+/// Provide duration since unix epoch in millisecond for timestamp inherent.
 #[cfg(feature = "std")]
 pub struct InherentDataProvider;