[FRAME] Introduce force_adjust_total_issuance (#3001)

Add `Balances::force_adjust_total_issuance` as preparation for fixing
https://github.com/polkadot-fellows/runtimes/issues/147.
Important changes in `substrate/frame/balances/src/lib.rs`.

TODO:
- [x] Update weights

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: command-bot <>
Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/frame/balances/src/tests/dispatchable_tests.rs

@@ -18,9 +18,16 @@
 //! Tests regarding the functionality of the dispatchables/extrinsics.
 
 use super::*;
-use frame_support::traits::tokens::Preservation::Expendable;
+use crate::{
+	AdjustmentDirection::{Decrease as Dec, Increase as Inc},
+	Event,
+};
+use frame_support::traits::{fungible::Unbalanced, tokens::Preservation::Expendable};
 use fungible::{hold::Mutate as HoldMutate, Inspect, Mutate};
 
+/// Alice account ID for more readable tests.
+const ALICE: u64 = 1;
+
 #[test]
 fn default_indexing_on_new_accounts_should_not_work2() {
 	ExtBuilder::default()
@@ -222,3 +229,109 @@ fn upgrade_accounts_should_work() {
 			assert_eq!(System::consumers(&7), 0);
 		});
 }
+
+#[test]
+#[docify::export]
+fn force_adjust_total_issuance_example() {
+	ExtBuilder::default().build_and_execute_with(|| {
+		// First we set the TotalIssuance to 64 by giving Alice a balance of 64.
+		assert_ok!(Balances::force_set_balance(RuntimeOrigin::root(), ALICE, 64));
+		let old_ti = Balances::total_issuance();
+		assert_eq!(old_ti, 64, "TI should be 64");
+
+		// Now test the increase:
+		assert_ok!(Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Inc, 32));
+		let new_ti = Balances::total_issuance();
+		assert_eq!(old_ti + 32, new_ti, "Should increase by 32");
+
+		// If Alice tries to call it, it errors:
+		assert_noop!(
+			Balances::force_adjust_total_issuance(RawOrigin::Signed(ALICE).into(), Inc, 32),
+			BadOrigin,
+		);
+	});
+}
+
+#[test]
+fn force_adjust_total_issuance_works() {
+	ExtBuilder::default().build_and_execute_with(|| {
+		assert_ok!(Balances::force_set_balance(RuntimeOrigin::root(), 1337, 64));
+		let ti = Balances::total_issuance();
+
+		// Increase works:
+		assert_ok!(Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Inc, 32));
+		assert_eq!(Balances::total_issuance(), ti + 32);
+		System::assert_last_event(RuntimeEvent::Balances(Event::TotalIssuanceForced {
+			old: 64,
+			new: 96,
+		}));
+
+		// Decrease works:
+		assert_ok!(Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Dec, 64));
+		assert_eq!(Balances::total_issuance(), ti - 32);
+		System::assert_last_event(RuntimeEvent::Balances(Event::TotalIssuanceForced {
+			old: 96,
+			new: 32,
+		}));
+	});
+}
+
+#[test]
+fn force_adjust_total_issuance_saturates() {
+	ExtBuilder::default().build_and_execute_with(|| {
+		assert_ok!(Balances::force_set_balance(RuntimeOrigin::root(), 1337, 64));
+		let ti = Balances::total_issuance();
+		let max = Balance::max_value();
+		assert_eq!(ti, 64);
+
+		// Increment saturates:
+		assert_ok!(Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Inc, max));
+		assert_ok!(Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Inc, 123));
+		assert_eq!(Balances::total_issuance(), max);
+
+		// Decrement saturates:
+		assert_ok!(Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Dec, max));
+		assert_ok!(Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Dec, 123));
+		assert_eq!(Balances::total_issuance(), 0);
+	});
+}
+
+#[test]
+fn force_adjust_total_issuance_rejects_zero_delta() {
+	ExtBuilder::default().build_and_execute_with(|| {
+		assert_noop!(
+			Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Inc, 0),
+			Error::<Test>::DeltaZero,
+		);
+		assert_noop!(
+			Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Dec, 0),
+			Error::<Test>::DeltaZero,
+		);
+	});
+}
+
+#[test]
+fn force_adjust_total_issuance_rejects_more_than_inactive() {
+	ExtBuilder::default().build_and_execute_with(|| {
+		assert_ok!(Balances::force_set_balance(RuntimeOrigin::root(), 1337, 64));
+		Balances::deactivate(16u32.into());
+
+		assert_eq!(Balances::total_issuance(), 64);
+		assert_eq!(Balances::active_issuance(), 48);
+
+		// Works with up to 48:
+		assert_ok!(Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Dec, 40),);
+		assert_ok!(Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Dec, 8),);
+		assert_eq!(Balances::total_issuance(), 16);
+		assert_eq!(Balances::active_issuance(), 0);
+		// Errors with more than 48:
+		assert_noop!(
+			Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Dec, 1),
+			Error::<Test>::IssuanceDeactivated,
+		);
+		// Increasing again increases the inactive issuance:
+		assert_ok!(Balances::force_adjust_total_issuance(RawOrigin::Root.into(), Inc, 10),);
+		assert_eq!(Balances::total_issuance(), 26);
+		assert_eq!(Balances::active_issuance(), 10);
+	});
+}

substrate/frame/balances/src/tests/mod.rs

@@ -126,8 +126,10 @@ impl pallet_transaction_payment::Config for Test {
 	type FeeMultiplierUpdate = ();
 }
 
+pub(crate) type Balance = u64;
+
 impl Config for Test {
-	type Balance = u64;
+	type Balance = Balance;
 	type DustRemoval = DustTrap;
 	type RuntimeEvent = RuntimeEvent;
 	type ExistentialDeposit = ExistentialDeposit;