Add Freeze/Thaw events and tests (#13779)

* Add Freeze/Thaw events and tests

* Remove duplicate docstring

* Correct spelling error

* Cargo fmt

* Use proper punctuation in docstring

Co-authored-by: Jegor Sidorenko <5252494+jsidorenko@users.noreply.github.com>

---------

Co-authored-by: Jegor Sidorenko <5252494+jsidorenko@users.noreply.github.com>
Co-authored-by: parity-processbot <>

frame/balances/src/lib.rs

@@ -337,6 +337,10 @@ pub mod pallet {
 		Locked { who: T::AccountId, amount: T::Balance },
 		/// Some balance was unlocked.
 		Unlocked { who: T::AccountId, amount: T::Balance },
+		/// Some balance was frozen.
+		Frozen { who: T::AccountId, amount: T::Balance },
+		/// Some balance was thawed.
+		Thawed { who: T::AccountId, amount: T::Balance },
 	}
 
 	#[pallet::error]
@@ -1084,21 +1088,32 @@ pub mod pallet {
 			who: &T::AccountId,
 			freezes: BoundedSlice<IdAmount<T::FreezeIdentifier, T::Balance>, T::MaxFreezes>,
 		) -> DispatchResult {
+			let mut prev_frozen = Zero::zero();
+			let mut after_frozen = Zero::zero();
 			let (_, maybe_dust) = Self::mutate_account(who, |b| {
+				prev_frozen = b.frozen;
 				b.frozen = Zero::zero();
 				for l in Locks::<T, I>::get(who).iter() {
 					b.frozen = b.frozen.max(l.amount);
 				}
 				for l in freezes.iter() {
 					b.frozen = b.frozen.max(l.amount);
 				}
+				after_frozen = b.frozen;
 			})?;
 			debug_assert!(maybe_dust.is_none(), "Not altering main balance; qed");
 			if freezes.is_empty() {
 				Freezes::<T, I>::remove(who);
 			} else {
 				Freezes::<T, I>::insert(who, freezes);
 			}
+			if prev_frozen > after_frozen {
+				let amount = prev_frozen.saturating_sub(after_frozen);
+				Self::deposit_event(Event::Thawed { who: who.clone(), amount });
+			} else if after_frozen > prev_frozen {
+				let amount = after_frozen.saturating_sub(prev_frozen);
+				Self::deposit_event(Event::Frozen { who: who.clone(), amount });
+			}
 			Ok(())
 		}
 

frame/balances/src/tests/fungible_tests.rs

@@ -397,3 +397,49 @@ fn unholding_frees_hold_slot() {
 			assert_ok!(Balances::hold(&TestId::Baz, &1, 10));
 		});
 }
+
+#[test]
+fn emit_events_with_changing_freezes() {
+	ExtBuilder::default().build_and_execute_with(|| {
+		let _ = Balances::set_balance(&1, 100);
+		System::reset_events();
+
+		// Freeze = [] --> [10]
+		assert_ok!(Balances::set_freeze(&TestId::Foo, &1, 10));
+		assert_eq!(events(), [RuntimeEvent::Balances(crate::Event::Frozen { who: 1, amount: 10 })]);
+
+		// Freeze = [10] --> [15]
+		assert_ok!(Balances::set_freeze(&TestId::Foo, &1, 15));
+		assert_eq!(events(), [RuntimeEvent::Balances(crate::Event::Frozen { who: 1, amount: 5 })]);
+
+		// Freeze = [15] --> [15, 20]
+		assert_ok!(Balances::set_freeze(&TestId::Bar, &1, 20));
+		assert_eq!(events(), [RuntimeEvent::Balances(crate::Event::Frozen { who: 1, amount: 5 })]);
+
+		// Freeze = [15, 20] --> [17, 20]
+		assert_ok!(Balances::set_freeze(&TestId::Foo, &1, 17));
+		for event in events() {
+			match event {
+				RuntimeEvent::Balances(crate::Event::Frozen { .. }) => {
+					assert!(false, "unexpected freeze event")
+				},
+				RuntimeEvent::Balances(crate::Event::Thawed { .. }) => {
+					assert!(false, "unexpected thaw event")
+				},
+				_ => continue,
+			}
+		}
+
+		// Freeze = [17, 20] --> [17, 15]
+		assert_ok!(Balances::set_freeze(&TestId::Bar, &1, 15));
+		assert_eq!(events(), [RuntimeEvent::Balances(crate::Event::Thawed { who: 1, amount: 3 })]);
+
+		// Freeze = [17, 15] --> [15]
+		assert_ok!(Balances::thaw(&TestId::Foo, &1));
+		assert_eq!(events(), [RuntimeEvent::Balances(crate::Event::Thawed { who: 1, amount: 2 })]);
+
+		// Freeze = [15] --> []
+		assert_ok!(Balances::thaw(&TestId::Bar, &1));
+		assert_eq!(events(), [RuntimeEvent::Balances(crate::Event::Thawed { who: 1, amount: 15 })]);
+	});
+}