feat(pallet): follow psp22 standard for decrease_allowance and burn

Cargo.toml

@@ -15,7 +15,11 @@ license = "Unlicense"
 repository = "https://github.com/r0gue-io/pop-node/"
 
 [workspace]
-exclude = [ "extension/contract", "pop-api", "tests/contracts" ]
+exclude = [
+	"extension/contract",
+	"pop-api",
+	"tests/contracts",
+]
 members = [
 	"integration-tests",
 	"node",

pallets/api/src/fungibles/mod.rs

@@ -17,6 +17,7 @@ type AccountIdOf<T> = <T as frame_system::Config>::AccountId;
 type TokenIdOf<T> = <AssetsOf<T> as Inspect<<T as frame_system::Config>::AccountId>>::AssetId;
 type TokenIdParameterOf<T> = <T as pallet_assets::Config<AssetsInstanceOf<T>>>::AssetIdParameter;
 type AssetsOf<T> = pallet_assets::Pallet<T, AssetsInstanceOf<T>>;
+type AssetsErrorOf<T> = pallet_assets::Error<T, AssetsInstanceOf<T>>;
 type AssetsInstanceOf<T> = <T as Config>::AssetsInstance;
 type AssetsWeightInfoOf<T> = <T as pallet_assets::Config<AssetsInstanceOf<T>>>::WeightInfo;
 type BalanceOf<T> = <AssetsOf<T> as Inspect<<T as frame_system::Config>::AccountId>>::Balance;
@@ -33,7 +34,7 @@ pub mod pallet {
 	};
 	use frame_system::pallet_prelude::*;
 	use sp_runtime::{
-		traits::{StaticLookup, Zero},
+		traits::{CheckedSub, StaticLookup, Zero},
 		Saturating,
 	};
 	use sp_std::vec::Vec;
@@ -338,13 +339,14 @@ pub mod pallet {
 			let token_param: TokenIdParameterOf<T> = token.clone().into();
 
 			// Cancel the approval and approve `new_allowance` if difference is more than zero.
+			let new_allowance =
+				current_allowance.checked_sub(&value).ok_or(AssetsErrorOf::<T>::Unapproved)?;
 			AssetsOf::<T>::cancel_approval(
 				origin.clone(),
 				token_param.clone(),
 				spender_source.clone(),
 			)
 			.map_err(|e| e.with_weight(WeightOf::<T>::approve(0, 1)))?;
-			let new_allowance = current_allowance.saturating_sub(value);
 			let weight = if new_allowance.is_zero() {
 				WeightOf::<T>::approve(0, 1)
 			} else {
@@ -467,6 +469,10 @@ pub mod pallet {
 			account: AccountIdOf<T>,
 			value: BalanceOf<T>,
 		) -> DispatchResult {
+			let current_balance = AssetsOf::<T>::balance(token.clone(), &account);
+			if current_balance < value {
+				return Err(AssetsErrorOf::<T>::BalanceLow.into());
+			}
 			AssetsOf::<T>::burn(
 				origin,
 				token.clone().into(),

pallets/api/src/fungibles/tests.rs

@@ -272,20 +272,27 @@ fn decrease_allowance_works() {
 				BadOrigin.with_weight(WeightInfo::approve(0, 0))
 			);
 		}
+		assets::create_mint_and_approve(owner, token, owner, value, spender, value);
+		assert_eq!(Assets::allowance(token, &owner, &spender), value);
 		// Check error works for `Assets::cancel_approval()`. No error test for `approve_transfer`
 		// because it is not possible.
+		assert_ok!(Assets::freeze_asset(signed(owner), token));
 		assert_noop!(
 			Fungibles::decrease_allowance(signed(owner), token, spender, value / 2),
-			AssetsError::Unknown.with_weight(WeightInfo::approve(0, 1))
+			AssetsError::AssetNotLive.with_weight(WeightInfo::approve(0, 1))
 		);
-		assets::create_mint_and_approve(owner, token, owner, value, spender, value);
-		assert_eq!(Assets::allowance(token, &owner, &spender), value);
+		assert_ok!(Assets::thaw_asset(signed(owner), token));
 		// Owner balance is not changed if decreased by zero.
 		assert_eq!(
 			Fungibles::decrease_allowance(signed(owner), token, spender, 0),
 			Ok(Some(WeightInfo::approve(0, 0)).into())
 		);
 		assert_eq!(Assets::allowance(token, &owner, &spender), value);
+		// "Unapproved" error is returned if the current allowance is less than `value`.
+		assert_noop!(
+			Fungibles::decrease_allowance(signed(owner), token, spender, value * 2),
+			AssetsError::Unapproved
+		);
 		// Decrease allowance successfully.
 		assert_eq!(
 			Fungibles::decrease_allowance(signed(owner), token, spender, value / 2),
@@ -295,13 +302,6 @@ fn decrease_allowance_works() {
 		System::assert_last_event(
 			Event::Approval { token, owner, spender, value: value / 2 }.into(),
 		);
-		// Saturating if current allowance is decreased more than the owner balance.
-		assert_eq!(
-			Fungibles::decrease_allowance(signed(owner), token, spender, value),
-			Ok(Some(WeightInfo::approve(0, 1)).into())
-		);
-		assert_eq!(Assets::allowance(token, &owner, &spender), 0);
-		System::assert_last_event(Event::Approval { token, owner, spender, value: 0 }.into());
 	});
 }
 
@@ -416,10 +416,17 @@ fn burn_works() {
 		let from = BOB;
 		let total_supply = value * 2;
 
-		// Check error works for `Assets::burn()`.
-		assert_noop!(Fungibles::burn(signed(owner), token, from, value), AssetsError::Unknown);
 		assets::create_and_mint_to(owner, token, from, total_supply);
 		assert_eq!(Assets::total_supply(TOKEN), total_supply);
+		// Check error works for `Assets::burn()`.
+		assert_ok!(Assets::freeze_asset(signed(owner), token));
+		assert_noop!(Fungibles::burn(signed(owner), token, from, value), AssetsError::AssetNotLive);
+		assert_ok!(Assets::thaw_asset(signed(owner), token));
+		// "BalanceLow" error is returned if the balance is less than `value`.
+		assert_noop!(
+			Fungibles::burn(signed(owner), token, from, total_supply * 2),
+			AssetsError::BalanceLow
+		);
 		let balance_before_burn = Assets::balance(token, &from);
 		assert_ok!(Fungibles::burn(signed(owner), token, from, value));
 		assert_eq!(Assets::total_supply(TOKEN), total_supply - value);
@@ -677,8 +684,8 @@ mod read_weights {
 }
 
 mod ensure_codec_indexes {
-	use super::{Encode, RuntimeCall, *};
-	use crate::{fungibles, fungibles::Call::*, mock::RuntimeCall::Fungibles};
+	use super::{Encode, *};
+	use crate::{fungibles, mock::RuntimeCall::Fungibles};
 
 	#[test]
 	fn ensure_read_variant_indexes() {

pop-api/integration-tests/src/fungibles/mod.rs

@@ -253,11 +253,6 @@ fn decrease_allowance_works() {
 		let addr = instantiate(CONTRACT, INIT_VALUE, vec![]);
 		let amount: Balance = 100 * UNIT;
 
-		// Token does not exist.
-		assert_eq!(
-			decrease_allowance(&addr, 0, &BOB, amount),
-			Err(Module { index: 52, error: [3, 0] }),
-		);
 		// Create token and mint `amount` to contract address, then approve Bob to spend `amount`.
 		let token = assets::create_mint_and_approve(&addr, 0, &addr, amount, &BOB, amount);
 		// Token is not live, i.e. frozen or being destroyed.