Account touch trait

frame/assets/src/functions.rs

@@ -308,17 +308,21 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 	}
 
 	/// Creates an account for `who` to hold asset `id` with a zero balance and takes a deposit.
+	///
+	/// If invoked `permissionless = true` than a depositor can be anyone, if `permissioned = false`
+	/// a depositor must be the asset's `Admin` or `Freezer`.
 	pub(super) fn do_touch(
 		id: T::AssetId,
 		who: T::AccountId,
 		depositor: T::AccountId,
+		permissionless: bool,
 	) -> DispatchResult {
 		ensure!(!Account::<T, I>::contains_key(id, &who), Error::<T, I>::AlreadyExists);
 		let deposit = T::AssetAccountDeposit::get();
 		let mut details = Asset::<T, I>::get(&id).ok_or(Error::<T, I>::Unknown)?;
 		ensure!(details.status == AssetStatus::Live, Error::<T, I>::AssetNotLive);
 		ensure!(
-			&depositor == &who || &depositor == &details.admin || &depositor == &details.freezer,
+			permissionless || &depositor == &details.admin || &depositor == &details.freezer,
 			Error::<T, I>::NoPermission
 		);
 		let reason = Self::new_account(&who, &mut details, Some((&depositor, deposit)))?;

frame/assets/src/lib.rs

@@ -200,7 +200,7 @@ impl<AssetId, AccountId> AssetsCallback<AssetId, AccountId> for () {}
 #[frame_support::pallet]
 pub mod pallet {
 	use super::*;
-	use frame_support::pallet_prelude::*;
+	use frame_support::{pallet_prelude::*, traits::AccountTouch};
 	use frame_system::pallet_prelude::*;
 
 	/// The current storage version.
@@ -1485,7 +1485,7 @@ pub mod pallet {
 		pub fn touch(origin: OriginFor<T>, id: T::AssetIdParameter) -> DispatchResult {
 			let who = ensure_signed(origin)?;
 			let id: T::AssetId = id.into();
-			Self::do_touch(id, who.clone(), who)
+			Self::do_touch(id, who.clone(), who, true)
 		}
 
 		/// Return the deposit (if any) of an asset account or a consumer reference (if any) of an
@@ -1575,8 +1575,7 @@ pub mod pallet {
 			let origin = ensure_signed(origin)?;
 			let who = T::Lookup::lookup(who)?;
 			let id: T::AssetId = id.into();
-
-			Self::do_touch(id, who, origin)
+			Self::do_touch(id, who, origin, false)
 		}
 
 		/// Return the deposit (if any) of a target asset account. Useful if you are the depositor.
@@ -1601,6 +1600,21 @@ pub mod pallet {
 			Self::do_refund_other(id, &who, &origin)
 		}
 	}
+
+	/// Implements [AccountTouch] trait.
+	/// Note that a depositor can be any account, without any specific privilege.
+	/// This implementation is supposed to be used only for creation of system accounts.
+	impl<T: Config<I>, I: 'static> AccountTouch<T::AssetId, T::AccountId> for Pallet<T, I> {
+		type Balance = DepositBalanceOf<T, I>;
+
+		fn deposit() -> Self::Balance {
+			T::AssetAccountDeposit::get()
+		}
+
+		fn touch(asset: T::AssetId, who: T::AccountId, depositor: T::AccountId) -> DispatchResult {
+			Self::do_touch(asset, who, depositor, true)
+		}
+	}
 }
 
 sp_core::generate_feature_enabled_macro!(runtime_benchmarks_enabled, feature = "runtime-benchmarks", $);

frame/support/src/traits.rs

@@ -55,8 +55,8 @@ pub use filter::{ClearFilterGuard, FilterStack, FilterStackGuard, InstanceFilter
 mod misc;
 pub use misc::{
 	defensive_prelude::{self, *},
-	Backing, ConstBool, ConstI128, ConstI16, ConstI32, ConstI64, ConstI8, ConstU128, ConstU16,
-	ConstU32, ConstU64, ConstU8, DefensiveMax, DefensiveMin, DefensiveSaturating,
+	AccountTouch, Backing, ConstBool, ConstI128, ConstI16, ConstI32, ConstI64, ConstI8, ConstU128,
+	ConstU16, ConstU32, ConstU64, ConstU8, DefensiveMax, DefensiveMin, DefensiveSaturating,
 	DefensiveTruncateFrom, EnsureInherentsAreFirst, EqualPrivilegeOnly, EstimateCallFee,
 	ExecuteBlock, ExtrinsicCall, Get, GetBacking, GetDefault, HandleLifetime, IsSubType, IsType,
 	Len, OffchainWorker, OnKilledAccount, OnNewAccount, PrivilegeCmp, SameOrOther, Time,

frame/support/src/traits/misc.rs

@@ -17,7 +17,7 @@
 
 //! Smaller traits used in FRAME which don't need their own file.
 
-use crate::dispatch::Parameter;
+use crate::dispatch::{DispatchResult, Parameter};
 use codec::{CompactLen, Decode, DecodeLimit, Encode, EncodeLike, Input, MaxEncodedLen};
 use impl_trait_for_tuples::impl_for_tuples;
 use scale_info::{build::Fields, meta_type, Path, Type, TypeInfo, TypeParameter};
@@ -1154,6 +1154,18 @@ impl<Hash> PreimageRecipient<Hash> for () {
 	fn unnote_preimage(_: &Hash) {}
 }
 
+/// Trait for creating an asset account with a deposit taken from a specified by client depositor.
+pub trait AccountTouch<AssetId, AccountId> {
+	/// The type for currency units of the deposit.
+	type Balance;
+
+	/// The deposit amount of a native currency required for creating an asset account.
+	fn deposit() -> Self::Balance;
+
+	/// Create an account for `who` of the `asset` with a deposit taken from the `depositor`.
+	fn touch(asset: AssetId, who: AccountId, depositor: AccountId) -> DispatchResult;
+}
+
 #[cfg(test)]
 mod test {
 	use super::*;