add validation for farming params update

Author: keithsue

x/farming/keeper/msg_server.go

@@ -221,6 +221,11 @@ func (m msgServer) UpdateParams(goCtx context.Context, msg *types.MsgUpdateParam
 	// get the current params
 	params := m.GetParams(ctx)
 
+	// validate params update
+	if err := types.ValidateParamsUpdate(params, msg.Params); err != nil {
+		return nil, err
+	}
+
 	// update params
 	m.SetParams(ctx, msg.Params)
 

x/farming/types/params.go

@@ -57,6 +57,15 @@ func (p Params) Validate() error {
 	return nil
 }
 
+// ValidateParamsUpdate validates the given params update
+func ValidateParamsUpdate(params Params, newParams Params) error {
+	if newParams.RewardPerEpoch.Denom != params.RewardPerEpoch.Denom {
+		return errorsmod.Wrap(ErrInvalidParams, "reward denom cannot be updated")
+	}
+
+	return nil
+}
+
 // validateEpochDuration validates the given epoch duration
 func validateEpochDuration(p Params) error {
 	if p.EpochDuration < 0 {