Fungibles and Non-Fungibles Create and Destroy Traits + Assets and Uniques Implementation (#9844)

* refactor `do_destroy`

* destroy trait

* refactor do_force_create

* impl create trait

* do not bleed weight into api

* Do the same for uniques

* add docs

substrate/frame/assets/src/functions.rs

@@ -478,4 +478,88 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		Self::deposit_event(Event::Transferred(id, source.clone(), dest.clone(), credit));
 		Ok(credit)
 	}
+
+	/// Create a new asset without taking a deposit.
+	///
+	/// * `id`: The `AssetId` you want the new asset to have. Must not already be in use.
+	/// * `owner`: The owner, issuer, admin, and freezer of this asset upon creation.
+	/// * `is_sufficient`: Whether this asset needs users to have an existential deposit to hold
+	///   this asset.
+	/// * `min_balance`: The minimum balance a user is allowed to have of this asset before they are
+	///   considered dust and cleaned up.
+	pub(super) fn do_force_create(
+		id: T::AssetId,
+		owner: T::AccountId,
+		is_sufficient: bool,
+		min_balance: T::Balance,
+	) -> DispatchResult {
+		ensure!(!Asset::<T, I>::contains_key(id), Error::<T, I>::InUse);
+		ensure!(!min_balance.is_zero(), Error::<T, I>::MinBalanceZero);
+
+		Asset::<T, I>::insert(
+			id,
+			AssetDetails {
+				owner: owner.clone(),
+				issuer: owner.clone(),
+				admin: owner.clone(),
+				freezer: owner.clone(),
+				supply: Zero::zero(),
+				deposit: Zero::zero(),
+				min_balance,
+				is_sufficient,
+				accounts: 0,
+				sufficients: 0,
+				approvals: 0,
+				is_frozen: false,
+			},
+		);
+		Self::deposit_event(Event::ForceCreated(id, owner));
+		Ok(())
+	}
+
+	/// Destroy an existing asset.
+	///
+	/// * `id`: The asset you want to destroy.
+	/// * `witness`: Witness data needed about the current state of the asset, used to confirm
+	///   complexity of the operation.
+	/// * `maybe_check_owner`: An optional check before destroying the asset, if the provided
+	///   account is the owner of that asset. Can be used for authorization checks.
+	pub(super) fn do_destroy(
+		id: T::AssetId,
+		witness: DestroyWitness,
+		maybe_check_owner: Option<T::AccountId>,
+	) -> Result<DestroyWitness, DispatchError> {
+		Asset::<T, I>::try_mutate_exists(id, |maybe_details| {
+			let mut details = maybe_details.take().ok_or(Error::<T, I>::Unknown)?;
+			if let Some(check_owner) = maybe_check_owner {
+				ensure!(details.owner == check_owner, Error::<T, I>::NoPermission);
+			}
+			ensure!(details.accounts <= witness.accounts, Error::<T, I>::BadWitness);
+			ensure!(details.sufficients <= witness.sufficients, Error::<T, I>::BadWitness);
+			ensure!(details.approvals <= witness.approvals, Error::<T, I>::BadWitness);
+
+			for (who, v) in Account::<T, I>::drain_prefix(id) {
+				Self::dead_account(id, &who, &mut details, v.sufficient);
+			}
+			debug_assert_eq!(details.accounts, 0);
+			debug_assert_eq!(details.sufficients, 0);
+
+			let metadata = Metadata::<T, I>::take(&id);
+			T::Currency::unreserve(
+				&details.owner,
+				details.deposit.saturating_add(metadata.deposit),
+			);
+
+			for ((owner, _), approval) in Approvals::<T, I>::drain_prefix((&id,)) {
+				T::Currency::unreserve(&owner, approval.deposit);
+			}
+			Self::deposit_event(Event::Destroyed(id));
+
+			Ok(DestroyWitness {
+				accounts: details.accounts,
+				sufficients: details.sufficients,
+				approvals: details.approvals,
+			})
+		})
+	}
 }

substrate/frame/assets/src/impl_fungibles.rs

@@ -147,3 +147,30 @@ impl<T: Config<I>, I: 'static> fungibles::Unbalanced<T::AccountId> for Pallet<T,
 		}
 	}
 }
+
+impl<T: Config<I>, I: 'static> fungibles::Create<T::AccountId> for Pallet<T, I> {
+	fn create(
+		id: T::AssetId,
+		admin: T::AccountId,
+		is_sufficient: bool,
+		min_balance: Self::Balance,
+	) -> DispatchResult {
+		Self::do_force_create(id, admin, is_sufficient, min_balance)
+	}
+}
+
+impl<T: Config<I>, I: 'static> fungibles::Destroy<T::AccountId> for Pallet<T, I> {
+	type DestroyWitness = DestroyWitness;
+
+	fn get_destroy_witness(asset: &T::AssetId) -> Option<Self::DestroyWitness> {
+		Asset::<T, I>::get(asset).map(|asset_details| asset_details.destroy_witness())
+	}
+
+	fn destroy(
+		id: T::AssetId,
+		witness: Self::DestroyWitness,
+		maybe_check_owner: Option<T::AccountId>,
+	) -> Result<Self::DestroyWitness, DispatchError> {
+		Self::do_destroy(id, witness, maybe_check_owner)
+	}
+}

substrate/frame/assets/src/lib.rs

@@ -143,6 +143,7 @@ use codec::HasCompact;
 use frame_support::{
 	dispatch::{DispatchError, DispatchResult},
 	ensure,
+	pallet_prelude::DispatchResultWithPostInfo,
 	traits::{
 		tokens::{fungibles, DepositConsequence, WithdrawConsequence},
 		BalanceStatus::Reserved,
@@ -437,29 +438,7 @@ pub mod pallet {
 		) -> DispatchResult {
 			T::ForceOrigin::ensure_origin(origin)?;
 			let owner = T::Lookup::lookup(owner)?;
-
-			ensure!(!Asset::<T, I>::contains_key(id), Error::<T, I>::InUse);
-			ensure!(!min_balance.is_zero(), Error::<T, I>::MinBalanceZero);
-
-			Asset::<T, I>::insert(
-				id,
-				AssetDetails {
-					owner: owner.clone(),
-					issuer: owner.clone(),
-					admin: owner.clone(),
-					freezer: owner.clone(),
-					supply: Zero::zero(),
-					deposit: Zero::zero(),
-					min_balance,
-					is_sufficient,
-					accounts: 0,
-					sufficients: 0,
-					approvals: 0,
-					is_frozen: false,
-				},
-			);
-			Self::deposit_event(Event::ForceCreated(id, owner));
-			Ok(())
+			Self::do_force_create(id, owner, is_sufficient, min_balance)
 		}
 
 		/// Destroy a class of fungible assets.
@@ -494,39 +473,13 @@ pub mod pallet {
 				Ok(_) => None,
 				Err(origin) => Some(ensure_signed(origin)?),
 			};
-			Asset::<T, I>::try_mutate_exists(id, |maybe_details| {
-				let mut details = maybe_details.take().ok_or(Error::<T, I>::Unknown)?;
-				if let Some(check_owner) = maybe_check_owner {
-					ensure!(details.owner == check_owner, Error::<T, I>::NoPermission);
-				}
-				ensure!(details.accounts <= witness.accounts, Error::<T, I>::BadWitness);
-				ensure!(details.sufficients <= witness.sufficients, Error::<T, I>::BadWitness);
-				ensure!(details.approvals <= witness.approvals, Error::<T, I>::BadWitness);
-
-				for (who, v) in Account::<T, I>::drain_prefix(id) {
-					Self::dead_account(id, &who, &mut details, v.sufficient);
-				}
-				debug_assert_eq!(details.accounts, 0);
-				debug_assert_eq!(details.sufficients, 0);
-
-				let metadata = Metadata::<T, I>::take(&id);
-				T::Currency::unreserve(
-					&details.owner,
-					details.deposit.saturating_add(metadata.deposit),
-				);
-
-				for ((owner, _), approval) in Approvals::<T, I>::drain_prefix((&id,)) {
-					T::Currency::unreserve(&owner, approval.deposit);
-				}
-				Self::deposit_event(Event::Destroyed(id));
-
-				Ok(Some(T::WeightInfo::destroy(
-					details.accounts.saturating_sub(details.sufficients),
-					details.sufficients,
-					details.approvals,
-				))
-				.into())
-			})
+			let details = Self::do_destroy(id, witness, maybe_check_owner)?;
+			Ok(Some(T::WeightInfo::destroy(
+				details.accounts.saturating_sub(details.sufficients),
+				details.sufficients,
+				details.approvals,
+			))
+			.into())
 		}
 
 		/// Mint assets of a particular class.