fix!: x/staking - remove delegation with amount is zero

CHANGELOG.md

@@ -148,6 +148,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### State Machine Breaking
 
+* (x/staking) [#10254](https://github.com/cosmos/cosmos-sdk/pull/10254) Instead of using the shares to determine if a delegation should be removed, use the truncated (token) amount.
 * (store) [#10247](https://github.com/cosmos/cosmos-sdk/pull/10247) Charge gas for the key length in gas meter.
 * (store) [#10218](https://github.com/cosmos/cosmos-sdk/pull/10218) Charge gas even when there are no entries while seeking.
 * (x/auth)[\#9596](https://github.com/cosmos/cosmos-sdk/pull/9596) Enable creating periodic vesting accounts with a transactions instead of requiring them to be created in genesis.

x/staking/genesis.go

@@ -34,8 +34,11 @@ func InitGenesis(
 	keeper.SetParams(ctx, data.Params)
 	keeper.SetLastTotalPower(ctx, data.LastTotalPower)
 
+	valCache := make(map[string]types.Validator, len(data.Validators))
+
 	for _, validator := range data.Validators {
 		keeper.SetValidator(ctx, validator)
+		valCache[validator.OperatorAddress] = validator
 
 		// Manually set indices for the first time
 		keeper.SetValidatorByConsAddr(ctx, validator)
@@ -64,6 +67,16 @@ func InitGenesis(
 	}
 
 	for _, delegation := range data.Delegations {
+		validator, ok := valCache[delegation.GetValidatorAddr().String()]
+		if !ok {
+			panic(fmt.Sprintf("expected %s validator to be found", delegation.GetValidatorAddr()))
+		}
+
+		// skip importing delegations with non-zero shares but zero token amounts
+		if !delegation.Shares.IsZero() && validator.TokensFromShares(delegation.Shares).TruncateInt().IsZero() {
+			continue
+		}
+
 		delegatorAddress, err := sdk.AccAddressFromBech32(delegation.DelegatorAddress)
 		if err != nil {
 			panic(err)

x/staking/keeper/delegation.go

@@ -680,8 +680,11 @@ func (k Keeper) Unbond(
 		validator = k.mustGetValidator(ctx, validator.GetOperator())
 	}
 
-	// remove the delegation
-	if delegation.Shares.IsZero() {
+	// Remove the delegation if the resulting shares yield a truncated zero amount
+	// of tokens in the delegation. Note, in this this case, the shares themselves
+	// may not be zero, but rather a small fractional amount. Otherwise, we update
+	// the delegation object.
+	if validator.TokensFromShares(delegation.Shares).TruncateInt().IsZero() || delegation.Shares.IsZero() {
 		err = k.RemoveDelegation(ctx, delegation)
 	} else {
 		k.SetDelegation(ctx, delegation)

x/staking/keeper/invariants.go

@@ -137,13 +137,11 @@ func PositiveDelegationInvariant(k Keeper) sdk.Invariant {
 		for _, delegation := range delegations {
 			if delegation.Shares.IsNegative() {
 				count++
-
 				msg += fmt.Sprintf("\tdelegation with negative shares: %+v\n", delegation)
 			}
 
 			if delegation.Shares.IsZero() {
 				count++
-
 				msg += fmt.Sprintf("\tdelegation with zero shares: %+v\n", delegation)
 			}
 		}