Auto-incremental CollectionId

frame/uniques/Cargo.toml

@@ -21,6 +21,7 @@ frame-support = { version = "4.0.0-dev", default-features = false, path = "../su
 frame-system = { version = "4.0.0-dev", default-features = false, path = "../system" }
 sp-runtime = { version = "6.0.0", default-features = false, path = "../../primitives/runtime" }
 sp-std = { version = "4.0.0", default-features = false, path = "../../primitives/std" }
+num-traits = { version = "0.2.15", default-features = false }
 
 [dev-dependencies]
 pallet-balances = { version = "4.0.0-dev", path = "../balances" }

frame/uniques/src/benchmarking.rs

@@ -42,13 +42,10 @@ fn create_collection<T: Config<I>, I: 'static>(
 	let caller_lookup = T::Lookup::unlookup(caller.clone());
 	let collection = T::Helper::collection(0);
 	T::Currency::make_free_balance_be(&caller, DepositBalanceOf::<T, I>::max_value());
-	assert!(Uniques::<T, I>::force_create(
-		SystemOrigin::Root.into(),
-		collection,
-		caller_lookup.clone(),
-		false,
-	)
-	.is_ok());
+	assert!(
+		Uniques::<T, I>::force_create(SystemOrigin::Root.into(), caller_lookup.clone(), false,)
+			.is_ok()
+	);
 	(collection, caller, caller_lookup)
 }
 
@@ -143,7 +140,7 @@ benchmarks_instance_pallet! {
 		whitelist_account!(caller);
 		let admin = T::Lookup::unlookup(caller.clone());
 		T::Currency::make_free_balance_be(&caller, DepositBalanceOf::<T, I>::max_value());
-		let call = Call::<T, I>::create { collection, admin };
+		let call = Call::<T, I>::create { admin };
 	}: { call.dispatch_bypass_filter(origin)? }
 	verify {
 		assert_last_event::<T, I>(Event::Created { collection: T::Helper::collection(0), creator: caller.clone(), owner: caller }.into());
@@ -152,7 +149,7 @@ benchmarks_instance_pallet! {
 	force_create {
 		let caller: T::AccountId = whitelisted_caller();
 		let caller_lookup = T::Lookup::unlookup(caller.clone());
-	}: _(SystemOrigin::Root, T::Helper::collection(0), caller_lookup, true)
+	}: _(SystemOrigin::Root, caller_lookup, true)
 	verify {
 		assert_last_event::<T, I>(Event::ForceCreated { collection: T::Helper::collection(0), owner: caller }.into());
 	}

frame/uniques/src/functions.rs

@@ -64,8 +64,6 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		free_holding: bool,
 		event: Event<T, I>,
 	) -> DispatchResult {
-		ensure!(!Collection::<T, I>::contains_key(collection), Error::<T, I>::InUse);
-
 		T::Currency::reserve(&owner, deposit)?;
 
 		Collection::<T, I>::insert(
@@ -85,10 +83,22 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		);
 
 		CollectionAccount::<T, I>::insert(&owner, &collection, ());
+
 		Self::deposit_event(event);
 		Ok(())
 	}
 
+	pub fn try_increment_id(
+		last_collection: T::CollectionId,
+	) -> Result<T::CollectionId, Error<T, I>> {
+		let new_collection = last_collection + T::CollectionId::one();
+
+		CollectionsCount::<T, I>::set(new_collection);
+		ensure!(!Collection::<T, I>::contains_key(new_collection), Error::<T, I>::InUse);
+
+		Ok(new_collection)
+	}
+
 	pub fn do_destroy_collection(
 		collection: T::CollectionId,
 		witness: DestroyWitness,

frame/uniques/src/lib.rs

@@ -52,6 +52,8 @@ use sp_runtime::{
 };
 use sp_std::prelude::*;
 
+use num_traits::{FromPrimitive, One, Unsigned};
+
 pub use pallet::*;
 pub use types::*;
 pub use weights::WeightInfo;
@@ -88,7 +90,13 @@ pub mod pallet {
 		type Event: From<Event<Self, I>> + IsType<<Self as frame_system::Config>::Event>;
 
 		/// Identifier for the collection of item.
-		type CollectionId: Member + Parameter + MaxEncodedLen + Copy;
+		type CollectionId: Member
+			+ Parameter
+			+ MaxEncodedLen
+			+ Copy
+			+ Default
+			+ Unsigned
+			+ FromPrimitive;
 
 		/// The type used to identify a unique item within a collection.
 		type ItemId: Member + Parameter + MaxEncodedLen + Copy;
@@ -250,6 +258,11 @@ pub mod pallet {
 	pub(super) type CollectionMaxSupply<T: Config<I>, I: 'static = ()> =
 		StorageMap<_, Blake2_128Concat, T::CollectionId, u32, OptionQuery>;
 
+	#[pallet::storage]
+	/// Stores the last CollectionId of the collections.
+	pub(super) type CollectionsCount<T: Config<I>, I: 'static = ()> =
+		StorageValue<_, T::CollectionId, ValueQuery>;
+
 	#[pallet::event]
 	#[pallet::generate_deposit(pub(super) fn deposit_event)]
 	pub enum Event<T: Config<I>, I: 'static = ()> {
@@ -400,7 +413,6 @@ pub mod pallet {
 		/// `ItemDeposit` funds of sender are reserved.
 		///
 		/// Parameters:
-		/// - `collection`: The identifier of the new collection. This must not be currently in use.
 		/// - `admin`: The admin of this collection. The admin is the initial address of each
 		/// member of the collection's admin team.
 		///
@@ -410,9 +422,11 @@ pub mod pallet {
 		#[pallet::weight(T::WeightInfo::create())]
 		pub fn create(
 			origin: OriginFor<T>,
-			collection: T::CollectionId,
 			admin: <T::Lookup as StaticLookup>::Source,
 		) -> DispatchResult {
+			let last_collection = CollectionsCount::<T, I>::get();
+			let collection = Self::try_increment_id(last_collection)?;
+
 			let owner = T::CreateOrigin::ensure_origin(origin, &collection)?;
 			let admin = T::Lookup::lookup(admin)?;
 
@@ -434,7 +448,6 @@ pub mod pallet {
 		///
 		/// Unlike `create`, no funds are reserved.
 		///
-		/// - `collection`: The identifier of the new item. This must not be currently in use.
 		/// - `owner`: The owner of this collection of items. The owner has full superuser
 		///   permissions
 		/// over this item, but may later change and configure the permissions using
@@ -446,13 +459,15 @@ pub mod pallet {
 		#[pallet::weight(T::WeightInfo::force_create())]
 		pub fn force_create(
 			origin: OriginFor<T>,
-			collection: T::CollectionId,
 			owner: <T::Lookup as StaticLookup>::Source,
 			free_holding: bool,
 		) -> DispatchResult {
 			T::ForceOrigin::ensure_origin(origin)?;
 			let owner = T::Lookup::lookup(owner)?;
 
+			let last_collection = CollectionsCount::<T, I>::get();
+			let collection = Self::try_increment_id(last_collection)?;
+
 			Self::do_create_collection(
 				collection,
 				owner.clone(),