Make the simulator create the new comission rate sensibly

PENDING.md

@@ -28,6 +28,7 @@ FEATURES
 
 * SDK
     * (#1336) Mechanism for SDK Users to configure their own Bech32 prefixes instead of using the default cosmos prefixes.
+    * [simulator] \#2682 MsgEditValidator now looks at the validator's max rate, thus it now succeeds a significant portion of the time
 
 * Tendermint
 

x/stake/simulation/msgs.go

@@ -26,11 +26,11 @@ func SimulateMsgCreateValidator(m auth.AccountKeeper, k stake.Keeper) simulation
 			Moniker: simulation.RandStringOfLength(r, 10),
 		}
 
-		maxCommission := sdk.NewInt(10)
+		maxCommission := sdk.NewDecWithPrec(r.Int63n(1000), 3)
 		commission := stake.NewCommissionMsg(
-			sdk.NewDecWithPrec(simulation.RandomAmount(r, maxCommission).Int64(), 1),
-			sdk.NewDecWithPrec(simulation.RandomAmount(r, maxCommission).Int64(), 1),
-			sdk.NewDecWithPrec(simulation.RandomAmount(r, maxCommission).Int64(), 1),
+			simulation.RandomDecAmount(r, maxCommission),
+			maxCommission,
+			simulation.RandomDecAmount(r, maxCommission),
 		)
 
 		acc := simulation.RandomAcc(r, accs)
@@ -85,11 +85,10 @@ func SimulateMsgEditValidator(k stake.Keeper) simulation.Operation {
 			Details:  simulation.RandStringOfLength(r, 10),
 		}
 
-		maxCommission := sdk.NewInt(10)
-		newCommissionRate := sdk.NewDecWithPrec(simulation.RandomAmount(r, maxCommission).Int64(), 1)
-
 		val := keeper.RandomValidator(r, k, ctx)
 		address := val.GetOperator()
+		newCommissionRate := simulation.RandomDecAmount(r, val.Commission.MaxRate)
+
 		msg := stake.MsgEditValidator{
 			Description:    description,
 			ValidatorAddr:  address,

x/stake/types/commission.go

@@ -11,7 +11,7 @@ type (
 	// Commission defines a commission parameters for a given validator.
 	Commission struct {
 		Rate          sdk.Dec   `json:"rate"`            // the commission rate charged to delegators
-		MaxRate       sdk.Dec   `json:"max_rate"`        // maximum commission rate which validator can ever charge
+		MaxRate       sdk.Dec   `json:"max_rate"`        // maximum commission rate which this validator can ever charge
 		MaxChangeRate sdk.Dec   `json:"max_change_rate"` // maximum daily increase of the validator commission
 		UpdateTime    time.Time `json:"update_time"`     // the last time the commission rate was changed
 	}