fix: emit credits_earned in unlock_assets event

docs/events.md

@@ -100,6 +100,7 @@ Emitted by `unlock_assets` when a user withdraws assets from the pool.
 | :--- | :--- | :--- |
 | `user` | `Address` | The wallet address that unlocked assets. |
 | `amount` | `i128` | The quantity of assets withdrawn in this call. |
+| `credits_earned` | `i128` | The credits accrued and checkpointed during this unlock call (i.e. the delta since the previous checkpoint). |
 | `total_credits` | `i128` | The user's checkpointed total credit balance at the time of withdrawal. |
 
 ### `paused`

soroban/contracts/farming-pool/src/lib.rs

@@ -1310,7 +1310,9 @@ impl FarmingPool {
             return Err(PoolError::LockPeriodNotElapsed);
         }
 
+        let credits_before = position.total_credits;
         checkpoint_position(&env, &user, &mut position);
+        let credits_earned = position.total_credits - credits_before;
         let total_credits = position.total_credits;
         position.amount -= amount;
 
@@ -1344,7 +1346,7 @@ impl FarmingPool {
 
         env.events().publish(
             (symbol_short!("pool"), symbol_short!("unlocked")),
-            (user.clone(), amount, total_credits),
+            (user.clone(), amount, credits_earned, total_credits),
         );
 
         record_stake_event(&env, &user, symbol_short!("unlock"), amount);

soroban/contracts/farming-pool/src/test.rs

@@ -1501,6 +1501,42 @@ fn test_unlock_assets_partial_keeps_remaining_position() {
     assert_eq!(t.token.balance(&t.contract_id), 300);
 }
 
+#[test]
+fn test_unlock_assets_emits_event_with_credits_earned() {
+    let t = setup(1, 1);
+    t.client.lock_assets(&t.user, &1_000);
+    advance_ledgers(&t.env, 10);
+    t.client.unlock_assets(&t.user, &1_000);
+
+    // The unlocked event must include credits_earned (the delta from this
+    // checkpoint) alongside total_credits so indexers can track credit
+    // distributions without storage scans.
+    assert_eq!(
+        t.env.events().all().filter_by_contract(&t.contract_id),
+        soroban_sdk::vec![
+            &t.env,
+            (
+                t.contract_id.clone(),
+                soroban_sdk::vec![
+                    &t.env,
+                    soroban_sdk::symbol_short!("pool").into_val(&t.env),
+                    soroban_sdk::symbol_short!("chkpt").into_val(&t.env)
+                ],
+                (t.user.clone(), 10_000i128, 10_000i128).into_val(&t.env),
+            ),
+            (
+                t.contract_id.clone(),
+                soroban_sdk::vec![
+                    &t.env,
+                    soroban_sdk::symbol_short!("pool").into_val(&t.env),
+                    soroban_sdk::symbol_short!("unlocked").into_val(&t.env)
+                ],
+                (t.user.clone(), 1_000i128, 10_000i128, 10_000i128).into_val(&t.env),
+            )
+        ]
+    );
+}
+
 // ── unlock_assets split-invariance (#123) ─────────────────────────────────────
 //
 // #75 covers *when* checkpoints happen (time-invariance); this covers a
@@ -1589,7 +1625,8 @@ fn test_unlock_assets_final_outcome_is_invariant_to_how_the_withdrawal_is_split(
                             soroban_sdk::symbol_short!("pool").into_val(&t.env),
                             soroban_sdk::symbol_short!("unlocked").into_val(&t.env)
                         ],
-                        (t.user.clone(), last_part, EXPECTED_TOTAL_CREDITS).into_val(&t.env),
+                        (t.user.clone(), last_part, EXPECTED_TOTAL_CREDITS, EXPECTED_TOTAL_CREDITS)
+                            .into_val(&t.env),
                     )
                 ],
                 "final cumulative total_credits must be identical across partitions {partition:?}",
@@ -1606,7 +1643,7 @@ fn test_unlock_assets_final_outcome_is_invariant_to_how_the_withdrawal_is_split(
                             soroban_sdk::symbol_short!("pool").into_val(&t.env),
                             soroban_sdk::symbol_short!("unlocked").into_val(&t.env)
                         ],
-                        (t.user.clone(), last_part, EXPECTED_TOTAL_CREDITS).into_val(&t.env),
+                        (t.user.clone(), last_part, 0i128, EXPECTED_TOTAL_CREDITS).into_val(&t.env),
                     )
                 ],
                 "final cumulative total_credits must be identical across partitions {partition:?}",