fix: ensure withdraw_rewards events are always emitted on reward with…

…drawal (backport cosmos#13323) (cosmos#13339)

* fix: ensure withdraw_rewards events are always emitted on reward withdrawal (cosmos#13323)

(cherry picked from commit c1c23a7)

# Conflicts:
#	CHANGELOG.md
#	tests/integration/distribution/keeper/delegation_test.go
#	testutil/sims/app_helpers.go
#	x/distribution/keeper/delegation.go
#	x/distribution/keeper/delegation_test.go
#	x/distribution/keeper/keeper.go

* fix changelog

* fix conflcits

Co-authored-by: Aleksandr Bezobchuk <alexanderbez@users.noreply.github.com>
Co-authored-by: Julien Robert <julien@rbrt.fr>

CHANGELOG.md

@@ -49,6 +49,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
+* [#13323](https://github.com/cosmos/cosmos-sdk/pull/13323) Ensure `withdraw_rewards` rewards are emitted from all actions that result in rewards being withdrawn.
 * [#13233](https://github.com/cosmos/cosmos-sdk/pull/13233) Add `--append` to `add-genesis-account` sub-command to append new tokens after an account is already created.
 * (x/group) [#13214](https://github.com/cosmos/cosmos-sdk/pull/13214) Add `withdraw-proposal` command to group module's CLI transaction commands.
 * (x/auth) [#13048](https://github.com/cosmos/cosmos-sdk/pull/13048) Add handling of AccountNumberStoreKeyPrefix to the simulation decoder.

x/distribution/keeper/delegation.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
-
 	"github.com/cosmos/cosmos-sdk/x/distribution/types"
 	stakingtypes "github.com/cosmos/cosmos-sdk/x/staking/types"
 )
@@ -162,13 +161,13 @@ func (k Keeper) withdrawDelegationRewards(ctx sdk.Context, val stakingtypes.Vali
 		)
 	}
 
-	// truncate coins, return remainder to community pool
-	coins, remainder := rewards.TruncateDecimal()
+	// truncate reward dec coins, return remainder to community pool
+	finalRewards, remainder := rewards.TruncateDecimal()
 
 	// add coins to user account
-	if !coins.IsZero() {
+	if !finalRewards.IsZero() {
 		withdrawAddr := k.GetDelegatorWithdrawAddr(ctx, del.GetDelegatorAddr())
-		err := k.bankKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, withdrawAddr, coins)
+		err := k.bankKeeper.SendCoinsFromModuleToAccount(ctx, types.ModuleName, withdrawAddr, finalRewards)
 		if err != nil {
 			return nil, err
 		}
@@ -189,5 +188,24 @@ func (k Keeper) withdrawDelegationRewards(ctx sdk.Context, val stakingtypes.Vali
 	// remove delegator starting info
 	k.DeleteDelegatorStartingInfo(ctx, del.GetValidatorAddr(), del.GetDelegatorAddr())
 
-	return coins, nil
+	if finalRewards.IsZero() {
+		baseDenom, _ := sdk.GetBaseDenom()
+		if baseDenom == "" {
+			baseDenom = sdk.DefaultBondDenom
+		}
+
+		// Note, we do not call the NewCoins constructor as we do not want the zero
+		// coin removed.
+		finalRewards = sdk.Coins{sdk.NewCoin(baseDenom, sdk.ZeroInt())}
+	}
+
+	ctx.EventManager().EmitEvent(
+		sdk.NewEvent(
+			types.EventTypeWithdrawRewards,
+			sdk.NewAttribute(sdk.AttributeKeyAmount, finalRewards.String()),
+			sdk.NewAttribute(types.AttributeKeyValidator, val.GetOperator().String()),
+		),
+	)
+
+	return finalRewards, nil
 }

x/distribution/keeper/delegation_test.go

@@ -684,19 +684,15 @@ func Test100PercentCommissionReward(t *testing.T) {
 	rewards, err := app.DistrKeeper.WithdrawDelegationRewards(ctx, sdk.AccAddress(valAddrs[0]), valAddrs[0])
 	require.NoError(t, err)
 
-	denom, _ := sdk.GetBaseDenom()
-	zeroRewards := sdk.Coins{
-		sdk.Coin{
-			Denom:  denom,
-			Amount: sdk.ZeroInt(),
-		},
-	}
+	zeroRewards := sdk.Coins{sdk.NewCoin(sdk.DefaultBondDenom, sdk.ZeroInt())}
 	require.True(t, rewards.IsEqual(zeroRewards))
+
 	events := ctx.EventManager().Events()
 	lastEvent := events[len(events)-1]
-	hasValue := false
+
+	var hasValue bool
 	for _, attr := range lastEvent.Attributes {
-		if string(attr.Key) == "amount" && string(attr.Value) == "0" {
+		if string(attr.Key) == "amount" && string(attr.Value) == "0stake" {
 			hasValue = true
 		}
 	}

x/distribution/keeper/keeper.go

@@ -96,22 +96,6 @@ func (k Keeper) WithdrawDelegationRewards(ctx sdk.Context, delAddr sdk.AccAddres
 		return nil, err
 	}
 
-	if rewards.IsZero() {
-		baseDenom, _ := sdk.GetBaseDenom()
-		rewards = sdk.Coins{sdk.Coin{
-			Denom:  baseDenom,
-			Amount: sdk.ZeroInt(),
-		}}