UnionOf types for merged fungible and fungibles implementations (…

…paritytech#2033)

Introduces `UnionOf` types, crafted to merge `fungible` and `fungibles`
implementations or two `fungibles` implementations into a single type
implementing `fungibles`.

This also addresses an issue where `ItemOf` initiates a double drop for
an imbalance type, leading to inaccurate total issuance accounting.

Find the application of these types in this PR -
[link](paritytech#2031), places in
code -
[1](https://github.com/paritytech/polkadot-sdk/blob/4ec7496fa2632385b08fae860fcf28a523a7b5de/cumulus/parachains/runtimes/assets/asset-hub-kusama/src/lib.rs#L327),
[2](https://github.com/paritytech/polkadot-sdk/blob/4ec7496fa2632385b08fae860fcf28a523a7b5de/cumulus/parachains/runtimes/assets/asset-hub-kusama/src/lib.rs#L343).

---------

Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: joepetrowski <joe@parity.io>
(cherry picked from commit 0b74812)

cumulus/parachains/runtimes/assets/common/src/local_and_foreign_assets.rs

@@ -318,10 +318,18 @@ where
 		}
 	}
 
+	fn should_touch(asset_id: MultiLocation, who: &AccountId) -> bool {
+		if let Some(asset_id) = LocalAssetIdConverter::convert(&asset_id) {
+			Assets::should_touch(asset_id, who)
+		} else {
+			ForeignAssets::should_touch(asset_id, who)
+		}
+	}
+
 	fn touch(
 		asset_id: MultiLocation,
-		who: AccountId,
-		depositor: AccountId,
+		who: &AccountId,
+		depositor: &AccountId,
 	) -> Result<(), DispatchError> {
 		if let Some(asset_id) = LocalAssetIdConverter::convert(&asset_id) {
 			Assets::touch(asset_id, who, depositor)

prdoc/pr_2033.prdoc

@@ -0,0 +1,14 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: "`UnionOf` types for merged `fungible` and `fungibles` implementations"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Introduces `UnionOf` types, crafted to merge `fungible` and `fungibles` implementations or two
+      `fungibles` implementations into a single type implementing `fungibles`. This also addresses
+      an issue where `ItemOf` initiates a double drop for an imbalance type, leading to inaccurate
+      total issuance accounting.
+
+crates: [ ]

substrate/frame/asset-conversion/src/lib.rs

@@ -417,15 +417,15 @@ pub mod pallet {
 			match T::MultiAssetIdConverter::try_convert(asset1) {
 				MultiAssetIdConversionResult::Converted(asset) =>
 					if !T::Assets::contains(&asset, &pool_account) {
-						T::Assets::touch(asset, pool_account.clone(), sender.clone())?
+						T::Assets::touch(asset, &pool_account, &sender)?
 					},
 				MultiAssetIdConversionResult::Unsupported(_) => Err(Error::<T>::UnsupportedAsset)?,
 				MultiAssetIdConversionResult::Native => (),
 			}
 			match T::MultiAssetIdConverter::try_convert(asset2) {
 				MultiAssetIdConversionResult::Converted(asset) =>
 					if !T::Assets::contains(&asset, &pool_account) {
-						T::Assets::touch(asset, pool_account.clone(), sender.clone())?
+						T::Assets::touch(asset, &pool_account, &sender)?
 					},
 				MultiAssetIdConversionResult::Unsupported(_) => Err(Error::<T>::UnsupportedAsset)?,
 				MultiAssetIdConversionResult::Native => (),
@@ -438,7 +438,7 @@ pub mod pallet {
 			NextPoolAssetId::<T>::set(Some(next_lp_token_id));
 
 			T::PoolAssets::create(lp_token.clone(), pool_account.clone(), false, 1u32.into())?;
-			T::PoolAssets::touch(lp_token.clone(), pool_account.clone(), sender.clone())?;
+			T::PoolAssets::touch(lp_token.clone(), &pool_account, &sender)?;
 
 			let pool_info = PoolInfo { lp_token: lp_token.clone() };
 			Pools::<T>::insert(pool_id.clone(), pool_info);

substrate/frame/assets/src/lib.rs

@@ -1648,8 +1648,20 @@ pub mod pallet {
 			T::AssetAccountDeposit::get()
 		}
 
-		fn touch(asset: T::AssetId, who: T::AccountId, depositor: T::AccountId) -> DispatchResult {
-			Self::do_touch(asset, who, depositor, false)
+		fn should_touch(asset: T::AssetId, who: &T::AccountId) -> bool {
+			match Asset::<T, I>::get(&asset) {
+				Some(info) if info.is_sufficient => false,
+				Some(_) => !Account::<T, I>::contains_key(asset, who),
+				_ => true,
+			}
+		}
+
+		fn touch(
+			asset: T::AssetId,
+			who: &T::AccountId,
+			depositor: &T::AccountId,
+		) -> DispatchResult {
+			Self::do_touch(asset, who.clone(), depositor.clone(), false)
 		}
 	}
 

substrate/frame/assets/src/tests.rs

@@ -28,6 +28,8 @@ use pallet_balances::Error as BalancesError;
 use sp_io::storage;
 use sp_runtime::{traits::ConvertInto, TokenError};
 
+mod sets;
+
 fn asset_ids() -> Vec<u32> {
 	let mut s: Vec<_> = Assets::asset_ids().collect();
 	s.sort();