pallet assets: optional auto-increment for the asset ID (#4757)

Introduce an optional auto-increment setup for the IDs of new assets.

---------

Co-authored-by: joe petrowski <[email protected]>
Co-authored-by: Bastian Köcher <[email protected]>

polkadot/xcm/xcm-builder/src/tests/pay/mock.rs

@@ -299,6 +299,7 @@ pub fn new_test_ext() -> sp_io::TestExternalities {
 			(1, TreasuryAccountId::get(), INITIAL_BALANCE),
 			(100, TreasuryAccountId::get(), INITIAL_BALANCE),
 		],
+		next_asset_id: None,
 	}
 	.assimilate_storage(&mut t)
 	.unwrap();

polkadot/xcm/xcm-runtime-apis/tests/mock.rs

@@ -389,6 +389,7 @@ pub fn new_test_ext_with_balances_and_assets(
 			(1, "Relay Token".into(), "RLY".into(), 12),
 		],
 		accounts: assets,
+		next_asset_id: None,
 	}
 	.assimilate_storage(&mut t)
 	.unwrap();

prdoc/pr_4757.prdoc

@@ -0,0 +1,18 @@
+title: "pallet assets: optional auto-increment for the asset ID"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Introduce an optional auto-increment setup for the IDs of new assets.
+
+crates:
+  - name: pallet-assets
+    bump: major
+  - name: staging-xcm-builder
+    bump: patch
+  - name: staging-xcm
+    bump: patch
+  - name: pallet-assets-freezer
+    bump: patch
+  - name: pallet-contracts
+    bump: patch

substrate/bin/node/cli/tests/res/default_genesis_config.json

@@ -81,12 +81,14 @@
   "assets": {
     "assets": [],
     "metadata": [],
-    "accounts": []
+    "accounts": [],
+    "nextAssetId": null
   },
   "poolAssets": {
     "assets": [],
     "metadata": [],
-    "accounts": []
+    "accounts": [],
+    "nextAssetId": null
   },
   "transactionStorage": {
     "byteFee": 10,

substrate/frame/assets-freezer/src/mock.rs

@@ -137,6 +137,7 @@ pub fn new_test_ext(execute: impl FnOnce()) -> sp_io::TestExternalities {
 			assets: vec![(1, 0, true, 1)],
 			metadata: vec![],
 			accounts: vec![(1, 1, 100)],
+			next_asset_id: None,
 		},
 		system: Default::default(),
 		balances: Default::default(),

substrate/frame/assets/Cargo.toml

@@ -17,6 +17,7 @@ targets = ["x86_64-unknown-linux-gnu"]
 
 [dependencies]
 codec = { workspace = true }
+impl-trait-for-tuples = "0.2.2"
 log = { workspace = true }
 scale-info = { features = ["derive"], workspace = true }
 sp-std = { workspace = true }

substrate/frame/assets/src/functions.rs

@@ -709,6 +709,9 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 	) -> DispatchResult {
 		ensure!(!Asset::<T, I>::contains_key(&id), Error::<T, I>::InUse);
 		ensure!(!min_balance.is_zero(), Error::<T, I>::MinBalanceZero);
+		if let Some(next_id) = NextAssetId::<T, I>::get() {
+			ensure!(id == next_id, Error::<T, I>::BadAssetId);
+		}
 
 		Asset::<T, I>::insert(
 			&id,

substrate/frame/assets/src/lib.rs

@@ -174,6 +174,7 @@ use sp_runtime::{
 };
 use sp_std::prelude::*;
 
+use core::marker::PhantomData;
 use frame_support::{
 	dispatch::DispatchResult,
 	ensure,
@@ -182,7 +183,7 @@ use frame_support::{
 	traits::{
 		tokens::{fungibles, DepositConsequence, WithdrawConsequence},
 		BalanceStatus::Reserved,
-		Currency, EnsureOriginWithArg, ReservableCurrency, StoredMap,
+		Currency, EnsureOriginWithArg, Incrementable, ReservableCurrency, StoredMap,
 	},
 };
 use frame_system::Config as SystemConfig;
@@ -206,8 +207,37 @@ pub trait AssetsCallback<AssetId, AccountId> {
 	}
 }
 
-/// Empty implementation in case no callbacks are required.
-impl<AssetId, AccountId> AssetsCallback<AssetId, AccountId> for () {}
+#[impl_trait_for_tuples::impl_for_tuples(10)]
+impl<AssetId, AccountId> AssetsCallback<AssetId, AccountId> for Tuple {
+	fn created(id: &AssetId, owner: &AccountId) -> Result<(), ()> {
+		for_tuples!( #( Tuple::created(id, owner)?; )* );
+		Ok(())
+	}
+
+	fn destroyed(id: &AssetId) -> Result<(), ()> {
+		for_tuples!( #( Tuple::destroyed(id)?; )* );
+		Ok(())
+	}
+}
+
+/// Auto-increment the [`NextAssetId`] when an asset is created.
+///
+/// This has not effect if the [`NextAssetId`] value is not present.
+pub struct AutoIncAssetId<T, I = ()>(PhantomData<(T, I)>);
+impl<T: Config<I>, I> AssetsCallback<T::AssetId, T::AccountId> for AutoIncAssetId<T, I>
+where
+	T::AssetId: Incrementable,
+{
+	fn created(_: &T::AssetId, _: &T::AccountId) -> Result<(), ()> {
+		let Some(next_id) = NextAssetId::<T, I>::get() else {
+			// Auto increment for the asset id is not enabled.
+			return Ok(());
+		};
+		let next_id = next_id.increment().ok_or(())?;
+		NextAssetId::<T, I>::put(next_id);
+		Ok(())
+	}
+}
 
 #[frame_support::pallet]
 pub mod pallet {
@@ -361,6 +391,11 @@ pub mod pallet {
 		type Extra: Member + Parameter + Default + MaxEncodedLen;
 
 		/// Callback methods for asset state change (e.g. asset created or destroyed)
+		///
+		/// Types implementing the [`AssetsCallback`] can be chained when listed together as a
+		/// tuple.
+		/// The [`AutoIncAssetId`] callback, in conjunction with the [`NextAssetId`], can be
+		/// used to set up auto-incrementing asset IDs for this collection.
 		type CallbackHandle: AssetsCallback<Self::AssetId, Self::AccountId>;
 
 		/// Weight information for extrinsics in this pallet.
@@ -415,6 +450,18 @@ pub mod pallet {
 		ValueQuery,
 	>;
 
+	/// The asset ID enforced for the next asset creation, if any present. Otherwise, this storage
+	/// item has no effect.
+	///
+	/// This can be useful for setting up constraints for IDs of the new assets. For example, by
+	/// providing an initial [`NextAssetId`] and using the [`crate::AutoIncAssetId`] callback, an
+	/// auto-increment model can be applied to all new asset IDs.
+	///
+	/// The initial next asset ID can be set using the [`GenesisConfig`] or the
+	/// [SetNextAssetId](`migration::next_asset_id::SetNextAssetId`) migration.
+	#[pallet::storage]
+	pub type NextAssetId<T: Config<I>, I: 'static = ()> = StorageValue<_, T::AssetId, OptionQuery>;
+
 	#[pallet::genesis_config]
 	#[derive(frame_support::DefaultNoBound)]
 	pub struct GenesisConfig<T: Config<I>, I: 'static = ()> {
@@ -424,6 +471,13 @@ pub mod pallet {
 		pub metadata: Vec<(T::AssetId, Vec<u8>, Vec<u8>, u8)>,
 		/// Genesis accounts: id, account_id, balance
 		pub accounts: Vec<(T::AssetId, T::AccountId, T::Balance)>,
+		/// Genesis [`NextAssetId`].
+		///
+		/// Refer to the [`NextAssetId`] item for more information.
+		///
+		/// This does not enforce the asset ID for the [assets](`GenesisConfig::assets`) within the
+		/// genesis config. It sets the [`NextAssetId`] after they have been created.
+		pub next_asset_id: Option<T::AssetId>,
 	}
 
 	#[pallet::genesis_build]
@@ -485,6 +539,10 @@ pub mod pallet {
 				);
 				assert!(result.is_ok());
 			}
+
+			if let Some(next_asset_id) = &self.next_asset_id {
+				NextAssetId::<T, I>::put(next_asset_id);
+			}
 		}
 	}
 
@@ -622,6 +680,8 @@ pub mod pallet {
 		NotFrozen,
 		/// Callback action resulted in error
 		CallbackFailed,
+		/// The asset ID must be equal to the [`NextAssetId`].
+		BadAssetId,
 	}
 
 	#[pallet::call(weight(<T as Config<I>>::WeightInfo))]
@@ -636,7 +696,7 @@ pub mod pallet {
 		///
 		/// Parameters:
 		/// - `id`: The identifier of the new asset. This must not be currently in use to identify
-		/// an existing asset.
+		/// an existing asset. If [`NextAssetId`] is set, then this must be equal to it.
 		/// - `admin`: The admin of this class of assets. The admin is the initial address of each
 		/// member of the asset class's admin team.
 		/// - `min_balance`: The minimum balance of this new asset that any single account must
@@ -659,6 +719,10 @@ pub mod pallet {
 			ensure!(!Asset::<T, I>::contains_key(&id), Error::<T, I>::InUse);
 			ensure!(!min_balance.is_zero(), Error::<T, I>::MinBalanceZero);
 
+			if let Some(next_id) = NextAssetId::<T, I>::get() {
+				ensure!(id == next_id, Error::<T, I>::BadAssetId);
+			}
+
 			let deposit = T::AssetDeposit::get();
 			T::Currency::reserve(&owner, deposit)?;
 
@@ -698,7 +762,7 @@ pub mod pallet {
 		/// Unlike `create`, no funds are reserved.
 		///
 		/// - `id`: The identifier of the new asset. This must not be currently in use to identify
-		/// an existing asset.
+		/// an existing asset. If [`NextAssetId`] is set, then this must be equal to it.
 		/// - `owner`: The owner of this class of assets. The owner has full superuser permissions
 		/// over this asset, but may later change and configure the permissions using
 		/// `transfer_ownership` and `set_team`.

substrate/frame/assets/src/migration.rs

@@ -22,6 +22,30 @@ use log;
 #[cfg(feature = "try-runtime")]
 use sp_runtime::TryRuntimeError;
 
+pub mod next_asset_id {
+	use super::*;
+	use sp_core::Get;
+
+	/// Set [`NextAssetId`] to the value of `ID` if [`NextAssetId`] does not exist yet.
+	pub struct SetNextAssetId<ID, T: Config<I>, I: 'static = ()>(
+		core::marker::PhantomData<(ID, T, I)>,
+	);
+	impl<ID, T: Config<I>, I: 'static> OnRuntimeUpgrade for SetNextAssetId<ID, T, I>
+	where
+		T::AssetId: Incrementable,
+		ID: Get<T::AssetId>,
+	{
+		fn on_runtime_upgrade() -> frame_support::weights::Weight {
+			if !NextAssetId::<T, I>::exists() {
+				NextAssetId::<T, I>::put(ID::get());
+				T::DbWeight::get().reads_writes(1, 1)
+			} else {
+				T::DbWeight::get().reads(1)
+			}
+		}
+	}
+}
+
 pub mod v1 {
 	use frame_support::{pallet_prelude::*, weights::Weight};
 

substrate/frame/assets/src/mock.rs

@@ -103,7 +103,7 @@ impl Config for Test {
 	type CreateOrigin = AsEnsureOriginWithArg<frame_system::EnsureSigned<u64>>;
 	type ForceOrigin = frame_system::EnsureRoot<u64>;
 	type Freezer = TestFreezer;
-	type CallbackHandle = AssetsCallbackHandle;
+	type CallbackHandle = (AssetsCallbackHandle, AutoIncAssetId<Test>);
 }
 
 use std::collections::HashMap;
@@ -167,6 +167,7 @@ pub(crate) fn new_test_ext() -> sp_io::TestExternalities {
 			// id, account_id, balance
 			(999, 1, 100),
 		],
+		next_asset_id: None,
 	};
 
 	config.assimilate_storage(&mut storage).unwrap();

substrate/frame/assets/src/tests.rs

@@ -1777,3 +1777,71 @@ fn asset_destroy_refund_existence_deposit() {
 		assert_eq!(Balances::reserved_balance(&admin), 0);
 	});
 }
+
+#[test]
+fn asset_id_cannot_be_reused() {
+	new_test_ext().execute_with(|| {
+		Balances::make_free_balance_be(&1, 100);
+		// Asset id can be reused till auto increment is not enabled.
+		assert_ok!(Assets::create(RuntimeOrigin::signed(1), 0, 1, 1));
+
+		assert_ok!(Assets::start_destroy(RuntimeOrigin::signed(1), 0));
+		assert_ok!(Assets::finish_destroy(RuntimeOrigin::signed(1), 0));
+
+		assert!(!Asset::<Test>::contains_key(0));
+
+		// Asset id `0` is reused.
+		assert_ok!(Assets::create(RuntimeOrigin::signed(1), 0, 1, 1));
+		assert!(Asset::<Test>::contains_key(0));
+
+		assert_ok!(Assets::start_destroy(RuntimeOrigin::signed(1), 0));
+		assert_ok!(Assets::finish_destroy(RuntimeOrigin::signed(1), 0));
+
+		assert!(!Asset::<Test>::contains_key(0));
+
+		// Enable auto increment. Next asset id must be 5.
+		pallet::NextAssetId::<Test>::put(5);
+
+		assert_noop!(Assets::create(RuntimeOrigin::signed(1), 0, 1, 1), Error::<Test>::BadAssetId);
+		assert_noop!(Assets::create(RuntimeOrigin::signed(1), 1, 1, 1), Error::<Test>::BadAssetId);
+		assert_noop!(
+			Assets::force_create(RuntimeOrigin::root(), 0, 1, false, 1),
+			Error::<Test>::BadAssetId
+		);
+		assert_noop!(
+			Assets::force_create(RuntimeOrigin::root(), 1, 1, true, 1),
+			Error::<Test>::BadAssetId
+		);
+
+		// Asset with id `5` is created.
+		assert_ok!(Assets::create(RuntimeOrigin::signed(1), 5, 1, 1));
+		assert!(Asset::<Test>::contains_key(5));
+
+		// Destroy asset with id `6`.
+		assert_ok!(Assets::start_destroy(RuntimeOrigin::signed(1), 5));
+		assert_ok!(Assets::finish_destroy(RuntimeOrigin::signed(1), 5));
+
+		assert!(!Asset::<Test>::contains_key(0));
+
+		// Asset id `5` cannot be reused.
+		assert_noop!(Assets::create(RuntimeOrigin::signed(1), 5, 1, 1), Error::<Test>::BadAssetId);
+
+		assert_ok!(Assets::create(RuntimeOrigin::signed(1), 6, 1, 1));
+		assert!(Asset::<Test>::contains_key(6));
+
+		// Destroy asset with id `6`.
+		assert_ok!(Assets::start_destroy(RuntimeOrigin::signed(1), 6));
+		assert_ok!(Assets::finish_destroy(RuntimeOrigin::signed(1), 6));
+
+		assert!(!Asset::<Test>::contains_key(6));
+
+		// Asset id `6` cannot be reused with force.
+		assert_noop!(
+			Assets::force_create(RuntimeOrigin::root(), 6, 1, false, 1),
+			Error::<Test>::BadAssetId
+		);
+
+		assert_ok!(Assets::force_create(RuntimeOrigin::root(), 7, 1, false, 1));
+		assert!(Asset::<Test>::contains_key(7));
+	});
+}

substrate/frame/contracts/mock-network/src/lib.rs

@@ -112,6 +112,7 @@ pub fn para_ext(para_id: u32) -> sp_io::TestExternalities {
 			(0u128, ALICE, INITIAL_BALANCE),
 			(0u128, relay_sovereign_account_id(), INITIAL_BALANCE),
 		],
+		next_asset_id: None,
 	}
 	.assimilate_storage(&mut t)
 	.unwrap();