From 84e91c12f2bde3efb91f6606d08644ee503bfec9 Mon Sep 17 00:00:00 2001
From: Shawn Tabrizi <shawntabrizi@gmail.com>
Date: Sat, 25 Sep 2021 17:15:54 -0400
Subject: [PATCH] Fix amount emitted in rebonded event

---
 frame/staking/src/lib.rs        |  6 ++--
 frame/staking/src/pallet/mod.rs |  4 +--
 frame/staking/src/tests.rs      | 59 +++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 4 deletions(-)

diff --git a/frame/staking/src/lib.rs b/frame/staking/src/lib.rs
index 136515a5d6168..d8e72e267ea9a 100644
--- a/frame/staking/src/lib.rs
+++ b/frame/staking/src/lib.rs
@@ -478,7 +478,9 @@ impl<AccountId, Balance: HasCompact + Copy + Saturating + AtLeast32BitUnsigned>
 	}
 
 	/// Re-bond funds that were scheduled for unlocking.
-	fn rebond(mut self, value: Balance) -> Self {
+	///
+	/// Returns the updated ledger, and the amount actually rebonded.
+	fn rebond(mut self, value: Balance) -> (Self, Balance) {
 		let mut unlocking_balance: Balance = Zero::zero();
 
 		while let Some(last) = self.unlocking.last_mut() {
@@ -499,7 +501,7 @@ impl<AccountId, Balance: HasCompact + Copy + Saturating + AtLeast32BitUnsigned>
 			}
 		}
 
-		self
+		(self, unlocking_balance)
 	}
 }
 
diff --git a/frame/staking/src/pallet/mod.rs b/frame/staking/src/pallet/mod.rs
index c71130a3492b1..dad958ccaea2f 100644
--- a/frame/staking/src/pallet/mod.rs
+++ b/frame/staking/src/pallet/mod.rs
@@ -1348,11 +1348,11 @@ pub mod pallet {
 			ensure!(!ledger.unlocking.is_empty(), Error::<T>::NoUnlockChunk);
 
 			let initial_unlocking = ledger.unlocking.len() as u32;
-			let ledger = ledger.rebond(value);
+			let (ledger, rebonded_value) = ledger.rebond(value);
 			// Last check: the new active amount of ledger must be more than ED.
 			ensure!(ledger.active >= T::Currency::minimum_balance(), Error::<T>::InsufficientBond);
 
-			Self::deposit_event(Event::<T>::Bonded(ledger.stash.clone(), value));
+			Self::deposit_event(Event::<T>::Bonded(ledger.stash.clone(), rebonded_value));
 
 			// NOTE: ledger must be updated prior to calling `Self::weight_of`.
 			Self::update_ledger(&controller, &ledger);
diff --git a/frame/staking/src/tests.rs b/frame/staking/src/tests.rs
index 5e7fe3d6266aa..38b760896d7d8 100644
--- a/frame/staking/src/tests.rs
+++ b/frame/staking/src/tests.rs
@@ -1517,6 +1517,65 @@ fn rebond_is_fifo() {
 	})
 }
 
+#[test]
+fn rebond_emits_right_value_in_event() {
+	// When a user calls rebond with more than can be rebonded, things succeed,
+	// and the rebond event emits the actual value rebonded.
+	ExtBuilder::default().nominate(false).build_and_execute(|| {
+		// Set payee to controller. avoids confusion
+		assert_ok!(Staking::set_payee(Origin::signed(10), RewardDestination::Controller));
+
+		// Give account 11 some large free balance greater than total
+		let _ = Balances::make_free_balance_be(&11, 1000000);
+
+		// confirm that 10 is a normal validator and gets paid at the end of the era.
+		mock::start_active_era(1);
+
+		// Unbond almost all of the funds in stash.
+		Staking::unbond(Origin::signed(10), 900).unwrap();
+		assert_eq!(
+			Staking::ledger(&10),
+			Some(StakingLedger {
+				stash: 11,
+				total: 1000,
+				active: 100,
+				unlocking: vec![UnlockChunk { value: 900, era: 1 + 3 }],
+				claimed_rewards: vec![],
+			})
+		);
+
+		// Re-bond less than the total
+		Staking::rebond(Origin::signed(10), 100).unwrap();
+		assert_eq!(
+			Staking::ledger(&10),
+			Some(StakingLedger {
+				stash: 11,
+				total: 1000,
+				active: 200,
+				unlocking: vec![UnlockChunk { value: 800, era: 1 + 3 }],
+				claimed_rewards: vec![],
+			})
+		);
+		// Event emitted should be correct
+		assert_eq!(*staking_events().last().unwrap(), Event::Bonded(11, 100));
+
+		// Re-bond way more than available
+		Staking::rebond(Origin::signed(10), 100_000).unwrap();
+		assert_eq!(
+			Staking::ledger(&10),
+			Some(StakingLedger {
+				stash: 11,
+				total: 1000,
+				active: 1000,
+				unlocking: vec![],
+				claimed_rewards: vec![],
+			})
+		);
+		// Event emitted should be correct, only 800
+		assert_eq!(*staking_events().last().unwrap(), Event::Bonded(11, 800));
+	});
+}
+
 #[test]
 fn reward_to_stake_works() {
 	ExtBuilder::default()