improve staking interface methods (#14023)

* improve staking interface methods

* fix

* fix

* fix build

* restart

* fix

---------

Co-authored-by: parity-processbot <>

substrate/primitives/staking/src/lib.rs

@@ -20,6 +20,8 @@
 //! A crate which contains primitives that are useful for implementation that uses staking
 //! approaches in general. Definitions related to sessions, slashing, etc go here.
 
+use scale_info::TypeInfo;
+use sp_core::RuntimeDebug;
 use sp_runtime::{DispatchError, DispatchResult};
 use sp_std::{collections::btree_map::BTreeMap, vec::Vec};
 
@@ -31,6 +33,18 @@ pub type SessionIndex = u32;
 /// Counter for the number of eras that have passed.
 pub type EraIndex = u32;
 
+/// Representation of the status of a staker.
+#[derive(RuntimeDebug, TypeInfo)]
+#[cfg_attr(feature = "std", derive(serde::Serialize, serde::Deserialize, PartialEq, Eq, Clone))]
+pub enum StakerStatus<AccountId> {
+	/// Chilling.
+	Idle,
+	/// Declaring desire in validate, i.e author blocks.
+	Validator,
+	/// Declaring desire to nominate, delegate, or generally approve of the given set of others.
+	Nominator(Vec<AccountId>),
+}
+
 /// Trait describing something that implements a hook for any operations to perform when a staker is
 /// slashed.
 pub trait OnStakerSlash<AccountId, Balance> {
@@ -57,7 +71,7 @@ impl<AccountId, Balance> OnStakerSlash<AccountId, Balance> for () {
 
 /// A struct that reflects stake that an account has in the staking system. Provides a set of
 /// methods to operate on it's properties. Aimed at making `StakingInterface` more concise.
-pub struct Stake<T: StakingInterface + ?Sized> {
+pub struct Stake<Balance> {
 	/// The total stake that `stash` has in the staking system. This includes the
 	/// `active` stake, and any funds currently in the process of unbonding via
 	/// [`StakingInterface::unbond`].
@@ -67,10 +81,10 @@ pub struct Stake<T: StakingInterface + ?Sized> {
 	/// This is only guaranteed to reflect the amount locked by the staking system. If there are
 	/// non-staking locks on the bonded pair's balance this amount is going to be larger in
 	/// reality.
-	pub total: T::Balance,
+	pub total: Balance,
 	/// The total amount of the stash's balance that will be at stake in any forthcoming
 	/// rounds.
-	pub active: T::Balance,
+	pub active: Balance,
 }
 
 /// A generic representation of a staking implementation.
@@ -109,21 +123,25 @@ pub trait StakingInterface {
 	/// This should be the latest planned era that the staking system knows about.
 	fn current_era() -> EraIndex;
 
-	/// Returns the stake of `who`.
-	fn stake(who: &Self::AccountId) -> Result<Stake<Self>, DispatchError>;
+	/// Returns the [`Stake`] of `who`.
+	fn stake(who: &Self::AccountId) -> Result<Stake<Self::Balance>, DispatchError>;
 
+	/// Total stake of a staker, `Err` if not a staker.
 	fn total_stake(who: &Self::AccountId) -> Result<Self::Balance, DispatchError> {
 		Self::stake(who).map(|s| s.total)
 	}
 
+	/// Total active portion of a staker's [`Stake`], `Err` if not a staker.
 	fn active_stake(who: &Self::AccountId) -> Result<Self::Balance, DispatchError> {
 		Self::stake(who).map(|s| s.active)
 	}
 
+	/// Returns whether a staker is unbonding, `Err` if not a staker at all.
 	fn is_unbonding(who: &Self::AccountId) -> Result<bool, DispatchError> {
 		Self::stake(who).map(|s| s.active != s.total)
 	}
 
+	/// Returns whether a staker is FULLY unbonding, `Err` if not a staker at all.
 	fn fully_unbond(who: &Self::AccountId) -> DispatchResult {
 		Self::unbond(who, Self::stake(who)?.active)
 	}
@@ -174,9 +192,17 @@ pub trait StakingInterface {
 	/// Checks whether an account `staker` has been exposed in an era.
 	fn is_exposed_in_era(who: &Self::AccountId, era: &EraIndex) -> bool;
 
+	/// Return the status of the given staker, `None` if not staked at all.
+	fn status(who: &Self::AccountId) -> Result<StakerStatus<Self::AccountId>, DispatchError>;
+
 	/// Get the nominations of a stash, if they are a nominator, `None` otherwise.
 	#[cfg(feature = "runtime-benchmarks")]
-	fn nominations(who: Self::AccountId) -> Option<Vec<Self::AccountId>>;
+	fn nominations(who: &Self::AccountId) -> Option<Vec<Self::AccountId>> {
+		match Self::status(who) {
+			Ok(StakerStatus::Nominator(t)) => Some(t),
+			_ => None,
+		}
+	}
 
 	#[cfg(feature = "runtime-benchmarks")]
 	fn add_era_stakers(