Add child-bounties pallet. (#10309)

* Extract child-bounties as a separate pallet.

* Initial tests added.

* More tests.

* Tests complete. Fixed curator fee issue.

* Fixed comments.

* Added benchmarks for child-bounties pallet.

* Added weights.

* Fixed formatting.

* Fixed comments.

* Re-run benchmarks for bounties pallet.

* Make cargo fmt happy again

* add max encoded len

* use event structs

* fmt

* fix compile

* Addressed review comments.

* Use config type instead of const in benchmarking.

* Addressed more review comments.

* Use ensure_can_withdraw instead of just checking min balance.

* fmt.

* Introduce ChildBountyCuratorDepositBase to avoid zero curator deposits for child bounties.

* Fix unassign curator logic for child-bounties.

* Added more tests for unassign curator.

* Reduce bounty description max length in node runtime.

* Updated weights for child bounties pallet.

* reduce indentation of unassign_curator

* more indentation reduction

* deduplicate slashing arms

* reintroduce ensure check

* add assertion to check that bad unassign origin fails

* formatting

* Updated comments.

Co-authored-by: Ricardo Rius <ricardo@parity.io>
Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Alexander Popiak <alexander.popiak@parity.io>

substrate/frame/bounties/src/lib.rs

@@ -123,6 +123,15 @@ pub struct Bounty<AccountId, Balance, BlockNumber> {
 	status: BountyStatus<AccountId, BlockNumber>,
 }
 
+impl<AccountId: PartialEq + Clone + Ord + Default, Balance, BlockNumber: Clone>
+	Bounty<AccountId, Balance, BlockNumber>
+{
+	/// Getter for bounty status, to be used for child bounties.
+	pub fn get_status(&self) -> BountyStatus<AccountId, BlockNumber> {
+		self.status.clone()
+	}
+}
+
 /// The status of a bounty proposal.
 #[derive(Encode, Decode, Clone, PartialEq, Eq, RuntimeDebug, TypeInfo)]
 pub enum BountyStatus<AccountId, BlockNumber> {
@@ -156,6 +165,15 @@ pub enum BountyStatus<AccountId, BlockNumber> {
 	},
 }
 
+/// The child-bounty manager.
+pub trait ChildBountyManager<Balance> {
+	/// Get the active child-bounties for a parent bounty.
+	fn child_bounties_count(bounty_id: BountyIndex) -> BountyIndex;
+
+	/// Get total curator fees of children-bounty curators.
+	fn children_curator_fees(bounty_id: BountyIndex) -> Balance;
+}
+
 #[frame_support::pallet]
 pub mod pallet {
 	use super::*;
@@ -202,6 +220,9 @@ pub mod pallet {
 
 		/// Weight information for extrinsics in this pallet.
 		type WeightInfo: WeightInfo;
+
+		/// The child-bounty manager.
+		type ChildBountyManager: ChildBountyManager<BalanceOf<Self>>;
 	}
 
 	#[pallet::error]
@@ -225,6 +246,8 @@ pub mod pallet {
 		PendingPayout,
 		/// The bounties cannot be claimed/closed because it's still in the countdown period.
 		Premature,
+		/// The bounty cannot be closed because it has active child-bounties.
+		HasActiveChildBounty,
 	}
 
 	#[pallet::event]
@@ -512,6 +535,13 @@ pub mod pallet {
 
 			Bounties::<T>::try_mutate_exists(bounty_id, |maybe_bounty| -> DispatchResult {
 				let mut bounty = maybe_bounty.as_mut().ok_or(Error::<T>::InvalidIndex)?;
+
+				// Ensure no active child-bounties before processing the call.
+				ensure!(
+					T::ChildBountyManager::child_bounties_count(bounty_id) == 0,
+					Error::<T>::HasActiveChildBounty
+				);
+
 				match &bounty.status {
 					BountyStatus::Active { curator, .. } => {
 						ensure!(signer == *curator, Error::<T>::RequireCurator);
@@ -563,7 +593,15 @@ pub mod pallet {
 					let payout = balance.saturating_sub(fee);
 					let err_amount = T::Currency::unreserve(&curator, bounty.curator_deposit);
 					debug_assert!(err_amount.is_zero());
-					let res = T::Currency::transfer(&bounty_account, &curator, fee, AllowDeath); // should not fail
+
+					// Get total child-bounties curator fees, and subtract it from master curator
+					// fee.
+					let children_fee = T::ChildBountyManager::children_curator_fees(bounty_id);
+					debug_assert!(children_fee <= fee);
+
+					let final_fee = fee.saturating_sub(children_fee);
+					let res =
+						T::Currency::transfer(&bounty_account, &curator, final_fee, AllowDeath); // should not fail
 					debug_assert!(res.is_ok());
 					let res =
 						T::Currency::transfer(&bounty_account, &beneficiary, payout, AllowDeath); // should not fail
@@ -609,6 +647,12 @@ pub mod pallet {
 				|maybe_bounty| -> DispatchResultWithPostInfo {
 					let bounty = maybe_bounty.as_ref().ok_or(Error::<T>::InvalidIndex)?;
 
+					// Ensure no active child-bounties before processing the call.
+					ensure!(
+						T::ChildBountyManager::child_bounties_count(bounty_id) == 0,
+						Error::<T>::HasActiveChildBounty
+					);
+
 					match &bounty.status {
 						BountyStatus::Proposed => {
 							// The reject origin would like to cancel a proposed bounty.
@@ -813,3 +857,14 @@ impl<T: Config> pallet_treasury::SpendFunds<T> for Pallet<T> {
 		*total_weight += <T as Config>::WeightInfo::spend_funds(bounties_len);
 	}
 }
+
+// Default impl for when ChildBounties is not being used in the runtime.
+impl<Balance: Zero> ChildBountyManager<Balance> for () {
+	fn child_bounties_count(_bounty_id: BountyIndex) -> BountyIndex {
+		Default::default()
+	}
+
+	fn children_curator_fees(_bounty_id: BountyIndex) -> Balance {
+		Zero::zero()
+	}
+}