Fix #351 — burn_for_basket early return for zero/empty recipients

acbu_burning/src/lib.rs

@@ -5,8 +5,8 @@ use soroban_sdk::{
 };
 
 use shared::{
-    calculate_fee, BurnEvent, ContractError, CurrencyCode, DataKey as SharedDataKey,
-    reentrancy_guard, BASIS_POINTS, CONTRACT_VERSION, DECIMALS, MIN_BURN_AMOUNT,
+    calculate_fee, reentrancy_guard, BurnEvent, ContractError, CurrencyCode,
+    DataKey as SharedDataKey, BASIS_POINTS, CONTRACT_VERSION, DECIMALS, MIN_BURN_AMOUNT,
     ORACLE_GET_ACBU_RATE_WITH_TS, ORACLE_GET_BASKET_WEIGHT, ORACLE_GET_CURRENCIES,
     ORACLE_GET_RATE_WITH_TS, ORACLE_GET_S_TOKEN_ADDR, RESERVE_IS_SUFFICIENT,
     TOKEN_GET_TOTAL_SUPPLY, UPDATE_INTERVAL_SECONDS,
@@ -230,7 +230,8 @@ impl BurningContract {
         user.require_auth();
 
         if recipients.is_empty() {
-            env.panic_with_error(ContractError::InvalidRecipient);
+            reentrancy_guard::release_guard(&env);
+            return Vec::new(&env);
         }
 
         // C-057: Enforce all recipient addresses are distinct.
@@ -505,7 +506,6 @@ impl BurningContract {
         env.storage().instance().set(&DATA_KEY.vault, &new_vault);
     }
 
-
     // -----------------------------------------------------------------------
     // Two-step admin rotation
     // -----------------------------------------------------------------------

acbu_burning/tests/fuzz_test.rs

@@ -1,29 +1,32 @@
 #![cfg(test)]
 
 use acbu_burning::{BurningContract, BurningContractClient};
-use shared::{CurrencyCode, DECIMALS};
-use soroban_sdk::{
-    testutils::Address as _,
-    Address, Env, Vec
-};
 use proptest::prelude::*;
+use shared::{CurrencyCode, DECIMALS};
+use soroban_sdk::{testutils::Address as _, Address, Env, Vec};
 
 mod mocks {
-    use soroban_sdk::{contract, contractimpl, Env, Address, Vec};
     use shared::CurrencyCode;
     use shared::DECIMALS;
+    use soroban_sdk::{contract, contractimpl, Address, Env, Vec};
 
     #[contract]
     pub struct MockOracle;
 
     #[contractimpl]
     impl MockOracle {
-        pub fn get_acbu_usd_rate(_env: Env) -> i128 { DECIMALS }
+        pub fn get_acbu_usd_rate(_env: Env) -> i128 {
+            DECIMALS
+        }
         pub fn get_acbu_usd_rate_with_timestamp(env: Env) -> (i128, u64) {
             (DECIMALS, env.ledger().timestamp())
         }
-        pub fn get_basket_weight(_env: Env, _c: CurrencyCode) -> i128 { 10_000 }
-        pub fn get_rate(_env: Env, _c: CurrencyCode) -> i128 { DECIMALS }
+        pub fn get_basket_weight(_env: Env, _c: CurrencyCode) -> i128 {
+            10_000
+        }
+        pub fn get_rate(_env: Env, _c: CurrencyCode) -> i128 {
+            DECIMALS
+        }
         pub fn get_rate_with_timestamp(env: Env, _c: CurrencyCode) -> (i128, u64) {
             (DECIMALS, env.ledger().timestamp())
         }
@@ -33,10 +36,15 @@ mod mocks {
             v
         }
         pub fn get_s_token_address(env: Env, _c: CurrencyCode) -> Address {
-            env.storage().instance().get(&soroban_sdk::symbol_short!("STK")).unwrap()
+            env.storage()
+                .instance()
+                .get(&soroban_sdk::symbol_short!("STK"))
+                .unwrap()
         }
         pub fn seed_stoken(env: Env, stoken: Address) {
-            env.storage().instance().set(&soroban_sdk::symbol_short!("STK"), &stoken);
+            env.storage()
+                .instance()
+                .set(&soroban_sdk::symbol_short!("STK"), &stoken);
         }
     }
 
@@ -56,15 +64,22 @@ mod mocks {
     #[contractimpl]
     impl MockACBUToken {
         pub fn get_total_supply(env: Env) -> i128 {
-            env.storage().instance().get(&soroban_sdk::symbol_short!("supply")).unwrap_or(0)
+            env.storage()
+                .instance()
+                .get(&soroban_sdk::symbol_short!("supply"))
+                .unwrap_or(0)
         }
         pub fn burn(env: Env, _from: Address, amount: i128) {
             let supply = Self::get_total_supply(env.clone());
-            env.storage().instance().set(&soroban_sdk::symbol_short!("supply"), &(supply - amount));
+            env.storage()
+                .instance()
+                .set(&soroban_sdk::symbol_short!("supply"), &(supply - amount));
         }
         pub fn mint(env: Env, _to: Address, amount: i128) {
             let supply = Self::get_total_supply(env.clone());
-            env.storage().instance().set(&soroban_sdk::symbol_short!("supply"), &(supply + amount));
+            env.storage()
+                .instance()
+                .set(&soroban_sdk::symbol_short!("supply"), &(supply + amount));
         }
     }
 }
@@ -74,17 +89,17 @@ proptest! {
     fn fuzz_redeem_basket_recipients(num_recipients in 0usize..20usize) {
         let env = Env::default();
         env.mock_all_auths();
-        
+
         let admin = Address::generate(&env);
         let oracle = env.register_contract(None, mocks::MockOracle);
         let reserve_tracker = env.register_contract(None, mocks::MockReserveTracker);
         let acbu_token = env.register_contract(None, mocks::MockACBUToken);
         let contract_id = env.register_contract(None, BurningContract);
         let client = BurningContractClient::new(&env, &contract_id);
-        
+
         let processor = Address::generate(&env);
         let vault = Address::generate(&env);
-        
+
         client.initialize(
             &admin,
             &oracle,
@@ -95,35 +110,37 @@ proptest! {
             &300,
             &100,
         );
-        
+
         let user = Address::generate(&env);
         let acbu_client = mocks::MockACBUTokenClient::new(&env, &acbu_token);
         acbu_client.mint(&user, &(1_000_000 * DECIMALS));
-        
+
         let stoken = env.register_stellar_asset_contract_v2(admin.clone()).address();
         let stoken_sac = soroban_sdk::token::StellarAssetClient::new(&env, &stoken);
         stoken_sac.mint(&vault, &(1_000_000 * DECIMALS));
-        
+
         let token = soroban_sdk::token::Client::new(&env, &stoken);
         token.approve(&vault, &contract_id, &1_000_000_000_000_000, &100u32);
-        
+
         let oracle_client = mocks::MockOracleClient::new(&env, &oracle);
         oracle_client.seed_stoken(&stoken);
-        
+
         let mut recipients = Vec::new(&env);
         for _ in 0..num_recipients {
             recipients.push_back(Address::generate(&env));
         }
-        
+
         let burn_amount = 100 * DECIMALS;
-        
+
         let res = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
             client.redeem_basket(&user, &recipients, &burn_amount);
         }));
-        
+
         // Since get_currencies returns exactly 1 item ("NGN"), the recipients list length must be exactly 1
         // as per the contract logic for basket redemptions.
-        if num_recipients != 1 {
+        if num_recipients == 0 {
+            assert!(res.is_ok());
+        } else if num_recipients != 1 {
             assert!(res.is_err());
         } else {
             assert!(res.is_ok());

acbu_burning/tests/test.rs

@@ -104,13 +104,14 @@ fn test_redeem_basket_requires_vault_allowance() {
 }
 
 #[test]
-fn test_redeem_basket_rejects_empty_recipients() {
+fn test_redeem_basket_allows_empty_recipients_as_noop() {
     let env = Env::default();
     let ctx = setup_test(&env);
 
     let empty: Vec<Address> = Vec::new(&env);
     let result = ctx.burning.try_redeem_basket(&ctx.user, &empty, &(100 * DECIMALS));
-    assert!(result.is_err());
+    assert!(result.is_ok());
+    assert_eq!(result.unwrap().unwrap().len(), 0);
 }
 
 #[test]