Fixed a bug where if there are dust AvailableStakingBalance, redeem a…

…mount is lost (#1470)

Co-authored-by: Roy Yang <roy@laminar.one>

modules/homa-lite/src/lib.rs

@@ -434,6 +434,7 @@ pub mod module {
 					Self::convert_staking_to_liquid(available_staking_balance)?,
 				);
 
+				let mut liquid_remaining = liquid_amount;
 				if Self::convert_liquid_to_staking(actual_liquid_amount)? > T::XcmUnbondFee::get() {
 					// Immediately redeem from the available_staking_balances
 					let actual_staking_amount = Self::convert_liquid_to_staking(actual_liquid_amount)?;
@@ -456,10 +457,10 @@ pub mod module {
 						actual_staking_amount,
 						actual_liquid_amount,
 					));
+					liquid_remaining = liquid_remaining.saturating_sub(actual_liquid_amount);
 				}
 
 				// Unredeemed requests are added to a queue.
-				let liquid_remaining = liquid_amount.saturating_sub(actual_liquid_amount);
 				if Self::liquid_amount_is_above_minimum_threshold(liquid_remaining) {
 					// Check if there's already a queued redeem request.
 					let (request_amount, _) = Self::redeem_requests(&who).unwrap_or((0, Permill::default()));

modules/homa-lite/src/tests.rs

@@ -799,3 +799,30 @@ fn staking_and_liquid_conversion_works() {
 		assert_eq!(HomaLite::convert_liquid_to_staking(5_000_000), Ok(1_000_000));
 	});
 }
+
+#[test]
+fn redeem_can_handle_dust_available_staking_currency() {
+	ExtBuilder::default().build().execute_with(|| {
+		// If AvailableStakingBalance is not enough to pay for the unbonding fee, ignore it.
+		// pub XcmUnbondFee: Balance = dollar(1);
+		assert_ok!(HomaLite::schedule_unbond(Origin::root(), 999_000_000, 0));
+		MockRelayBlockNumberProvider::set(0);
+		HomaLite::on_idle(MockRelayBlockNumberProvider::get(), 5_000_000_000);
+
+		assert_eq!(AvailableStakingBalance::<Runtime>::get(), 999_000_000);
+
+		// Ignore the dust AvailableStakingBalance and put the full amount onto the queue.
+		assert_ok!(HomaLite::request_redeem(
+			Origin::signed(ROOT),
+			dollar(1000),
+			Permill::zero()
+		));
+
+		assert_eq!(HomaLite::redeem_requests(ROOT), Some((dollar(1000), Permill::zero())));
+		System::assert_last_event(Event::HomaLite(crate::Event::RedeemRequested(
+			ROOT,
+			dollar(1000),
+			Permill::zero(),
+		)));
+	});
+}