refactor: remove weird casting for staking.Keeper in slashing and dis…

…tribution (#12973)

## Description

Both slashing and distribution simulator is using ugly casting from the nice interface type to:

 ```go
stakeKeeper := sk.(*stakingkeeper.Keeper)
```

This creates additional dependency for `staking/keeper` package in other modules, and requires type of a specific type (here reference type, in 0.46 it's even worse - because it uses object type).

EXTRA:
 * removed `stakingkeepr.RandomValidator` function (which btw, was also weird, because it was in the keeper module and required Keeper as an argument) and created generic `testutil.RandSliceElem` function.


---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.*

I have...

- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/main/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

CHANGELOG.md

@@ -42,6 +42,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (x/authz) [#12648](https://github.com/cosmos/cosmos-sdk/pull/12648) Add an allow list, an optional list of addresses allowed to receive bank assests via authz MsgSend grant.
 * (cli) [#12028](https://github.com/cosmos/cosmos-sdk/pull/12028) Add the `tendermint key-migrate` to perform Tendermint v0.35 DB key migration.
 * (sdk.Coins) [#12627](https://github.com/cosmos/cosmos-sdk/pull/12627) Make a Denoms method on sdk.Coins.
+* (testutil) [#12973](https://github.com/cosmos/cosmos-sdk/pull/12973) Add generic `testutil.RandSliceElem` function which selects a random element from the list.
 
 ### Improvements
 
@@ -111,6 +112,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (x/modules) Remove all LegacyQueries and related code from modules
 * (store) [#11825](https://github.com/cosmos/cosmos-sdk/pull/11825) Make extension snapshotter interface safer to use, renamed the util function `WriteExtensionItem` to `WriteExtensionPayload`.
 * (codec) [#12964](https://github.com/cosmos/cosmos-sdk/pull/12964) `ProtoCodec.MarshalInterface` now returns an error when serializing unregistered types and a subsequent `ProtoCodec.UnmarshalInterface` would fail.
+* (x/staking) [#12973](https://github.com/cosmos/cosmos-sdk/pull/12973) Removed `stakingkeeper.RandomValidator`. Use `testutil.RandSliceElem(r, sk.GetAllValidators(ctx))` instead.
 
 ### CLI Breaking Changes
 

go.work.sum

@@ -1 +1 @@
-github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0 h1:Ovs26xHkKqVztRpIrF/92BcuyuQ/YW4NSIpoGtfXNho=
+github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0 h1:Ovs26xHkKqVztRpIrF/92BcuyuQ/YW4NSIpoGtfXNho=

testutil/list.go

@@ -0,0 +1,12 @@
+package testutil
+
+import "math/rand"
+
+func RandSliceElem[E any](r *rand.Rand, elems []E) (E, bool) {
+	if len(elems) == 0 {
+		var e E
+		return e, false
+	}
+
+	return elems[r.Intn(len(elems))], true
+}

x/distribution/simulation/operations.go

@@ -8,14 +8,14 @@ import (
 	"github.com/cosmos/cosmos-sdk/client"
 	"github.com/cosmos/cosmos-sdk/codec"
 	codectypes "github.com/cosmos/cosmos-sdk/codec/types"
+	"github.com/cosmos/cosmos-sdk/testutil"
 	simtestutil "github.com/cosmos/cosmos-sdk/testutil/sims"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
 	"github.com/cosmos/cosmos-sdk/x/auth/tx"
 	"github.com/cosmos/cosmos-sdk/x/distribution/keeper"
 	"github.com/cosmos/cosmos-sdk/x/distribution/types"
 	"github.com/cosmos/cosmos-sdk/x/simulation"
-	stakingkeeper "github.com/cosmos/cosmos-sdk/x/staking/keeper"
 )
 
 // Simulation operation weights constants
@@ -58,8 +58,6 @@ func WeightedOperations(appParams simtypes.AppParams, cdc codec.JSONCodec, ak ty
 		},
 	)
 
-	stakeKeeper := sk.(*stakingkeeper.Keeper)
-
 	interfaceRegistry := codectypes.NewInterfaceRegistry()
 	txConfig := tx.NewTxConfig(codec.NewProtoCodec(interfaceRegistry), tx.DefaultSignModes)
 
@@ -70,15 +68,15 @@ func WeightedOperations(appParams simtypes.AppParams, cdc codec.JSONCodec, ak ty
 		),
 		simulation.NewWeightedOperation(
 			weightMsgWithdrawDelegationReward,
-			SimulateMsgWithdrawDelegatorReward(txConfig, ak, bk, k, stakeKeeper),
+			SimulateMsgWithdrawDelegatorReward(txConfig, ak, bk, k, sk),
 		),
 		simulation.NewWeightedOperation(
 			weightMsgWithdrawValidatorCommission,
-			SimulateMsgWithdrawValidatorCommission(txConfig, ak, bk, k, stakeKeeper),
+			SimulateMsgWithdrawValidatorCommission(txConfig, ak, bk, k, sk),
 		),
 		simulation.NewWeightedOperation(
 			weightMsgFundCommunityPool,
-			SimulateMsgFundCommunityPool(txConfig, ak, bk, k, stakeKeeper),
+			SimulateMsgFundCommunityPool(txConfig, ak, bk, k, sk),
 		),
 	}
 }
@@ -120,7 +118,7 @@ func SimulateMsgSetWithdrawAddress(txConfig client.TxConfig, ak types.AccountKee
 }
 
 // SimulateMsgWithdrawDelegatorReward generates a MsgWithdrawDelegatorReward with random values.
-func SimulateMsgWithdrawDelegatorReward(txConfig client.TxConfig, ak types.AccountKeeper, bk types.BankKeeper, k keeper.Keeper, sk *stakingkeeper.Keeper) simtypes.Operation {
+func SimulateMsgWithdrawDelegatorReward(txConfig client.TxConfig, ak types.AccountKeeper, bk types.BankKeeper, k keeper.Keeper, sk types.StakingKeeper) simtypes.Operation {
 	return func(
 		r *rand.Rand, app *baseapp.BaseApp, ctx sdk.Context, accs []simtypes.Account, chainID string,
 	) (simtypes.OperationMsg, []simtypes.FutureOperation, error) {
@@ -162,11 +160,11 @@ func SimulateMsgWithdrawDelegatorReward(txConfig client.TxConfig, ak types.Accou
 }
 
 // SimulateMsgWithdrawValidatorCommission generates a MsgWithdrawValidatorCommission with random values.
-func SimulateMsgWithdrawValidatorCommission(txConfig client.TxConfig, ak types.AccountKeeper, bk types.BankKeeper, k keeper.Keeper, sk *stakingkeeper.Keeper) simtypes.Operation {
+func SimulateMsgWithdrawValidatorCommission(txConfig client.TxConfig, ak types.AccountKeeper, bk types.BankKeeper, k keeper.Keeper, sk types.StakingKeeper) simtypes.Operation {
 	return func(
 		r *rand.Rand, app *baseapp.BaseApp, ctx sdk.Context, accs []simtypes.Account, chainID string,
 	) (simtypes.OperationMsg, []simtypes.FutureOperation, error) {
-		validator, ok := stakingkeeper.RandomValidator(r, sk, ctx)
+		validator, ok := testutil.RandSliceElem(r, sk.GetAllValidators(ctx))
 		if !ok {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgWithdrawValidatorCommission, "random validator is not ok"), nil, nil
 		}
@@ -207,7 +205,7 @@ func SimulateMsgWithdrawValidatorCommission(txConfig client.TxConfig, ak types.A
 
 // SimulateMsgFundCommunityPool simulates MsgFundCommunityPool execution where
 // a random account sends a random amount of its funds to the community pool.
-func SimulateMsgFundCommunityPool(txConfig client.TxConfig, ak types.AccountKeeper, bk types.BankKeeper, k keeper.Keeper, sk *stakingkeeper.Keeper) simtypes.Operation {
+func SimulateMsgFundCommunityPool(txConfig client.TxConfig, ak types.AccountKeeper, bk types.BankKeeper, k keeper.Keeper, sk types.StakingKeeper) simtypes.Operation {
 	return func(
 		r *rand.Rand, app *baseapp.BaseApp, ctx sdk.Context, accs []simtypes.Account, chainID string,
 	) (simtypes.OperationMsg, []simtypes.FutureOperation, error) {

x/distribution/types/expected_keepers.go

@@ -47,6 +47,8 @@ type StakingKeeper interface {
 		fn func(index int64, delegation stakingtypes.DelegationI) (stop bool))
 
 	GetAllSDKDelegations(ctx sdk.Context) []stakingtypes.Delegation
+	GetAllValidators(ctx sdk.Context) (validators []stakingtypes.Validator)
+	GetAllDelegatorDelegations(ctx sdk.Context, delegator sdk.AccAddress) []stakingtypes.Delegation
 }
 
 // StakingHooks event hooks for staking validator object (noalias)

x/slashing/simulation/operations.go

@@ -7,14 +7,14 @@ import (
 	"github.com/cosmos/cosmos-sdk/baseapp"
 	"github.com/cosmos/cosmos-sdk/codec"
 	codectypes "github.com/cosmos/cosmos-sdk/codec/types"
+	"github.com/cosmos/cosmos-sdk/testutil"
 	simtestutil "github.com/cosmos/cosmos-sdk/testutil/sims"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
 	"github.com/cosmos/cosmos-sdk/x/auth/tx"
 	"github.com/cosmos/cosmos-sdk/x/simulation"
 	"github.com/cosmos/cosmos-sdk/x/slashing/keeper"
 	"github.com/cosmos/cosmos-sdk/x/slashing/types"
-	stakingkeeper "github.com/cosmos/cosmos-sdk/x/staking/keeper"
 )
 
 // Simulation operation weights constants
@@ -40,18 +40,18 @@ func WeightedOperations(
 	return simulation.WeightedOperations{
 		simulation.NewWeightedOperation(
 			weightMsgUnjail,
-			SimulateMsgUnjail(codec.NewProtoCodec(interfaceRegistry), ak, bk, k, sk.(*stakingkeeper.Keeper)),
+			SimulateMsgUnjail(codec.NewProtoCodec(interfaceRegistry), ak, bk, k, sk),
 		),
 	}
 }
 
 // SimulateMsgUnjail generates a MsgUnjail with random values
-func SimulateMsgUnjail(cdc *codec.ProtoCodec, ak types.AccountKeeper, bk types.BankKeeper, k keeper.Keeper, sk *stakingkeeper.Keeper) simtypes.Operation {
+func SimulateMsgUnjail(cdc *codec.ProtoCodec, ak types.AccountKeeper, bk types.BankKeeper, k keeper.Keeper, sk types.StakingKeeper) simtypes.Operation {
 	return func(
 		r *rand.Rand, app *baseapp.BaseApp, ctx sdk.Context,
 		accs []simtypes.Account, chainID string,
 	) (simtypes.OperationMsg, []simtypes.FutureOperation, error) {
-		validator, ok := stakingkeeper.RandomValidator(r, sk, ctx)
+		validator, ok := testutil.RandSliceElem(r, sk.GetAllValidators(ctx))
 		if !ok {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgUnjail, "validator is not ok"), nil, nil // skip
 		}

x/slashing/types/expected_keepers.go

@@ -50,6 +50,7 @@ type StakingKeeper interface {
 	// Delegation allows for getting a particular delegation for a given validator
 	// and delegator outside the scope of the staking module.
 	Delegation(sdk.Context, sdk.AccAddress, sdk.ValAddress) stakingtypes.DelegationI
+	GetAllValidators(ctx sdk.Context) (validators []stakingtypes.Validator)
 
 	// MaxValidators returns the maximum amount of bonded validators
 	MaxValidators(sdk.Context) uint32

x/staking/keeper/test_common.go

@@ -2,7 +2,6 @@ package keeper // noalias
 
 import (
 	"bytes"
-	"math/rand"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/x/staking/types"
@@ -55,15 +54,3 @@ func TestingUpdateValidator(keeper *Keeper, ctx sdk.Context, validator types.Val
 
 	return validator
 }
-
-// RandomValidator returns a random validator given access to the keeper and ctx
-func RandomValidator(r *rand.Rand, keeper *Keeper, ctx sdk.Context) (val types.Validator, ok bool) {
-	vals := keeper.GetAllValidators(ctx)
-	if len(vals) == 0 {
-		return types.Validator{}, false
-	}
-
-	i := r.Intn(len(vals))
-
-	return vals[i], true
-}

x/staking/simulation/operations.go

@@ -8,6 +8,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/baseapp"
 	"github.com/cosmos/cosmos-sdk/codec"
 	simappparams "github.com/cosmos/cosmos-sdk/simapp/params"
+	"github.com/cosmos/cosmos-sdk/testutil"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	simtypes "github.com/cosmos/cosmos-sdk/types/simulation"
 	"github.com/cosmos/cosmos-sdk/x/simulation"
@@ -192,13 +193,12 @@ func SimulateMsgEditValidator(ak types.AccountKeeper, bk types.BankKeeper, k *ke
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgEditValidator, "number of validators equal zero"), nil, nil
 		}
 
-		val, ok := keeper.RandomValidator(r, k, ctx)
+		val, ok := testutil.RandSliceElem(r, k.GetAllValidators(ctx))
 		if !ok {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgEditValidator, "unable to pick a validator"), nil, nil
 		}
 
 		address := val.GetOperator()
-
 		newCommissionRate := simtypes.RandomDecAmount(r, val.Commission.MaxRate)
 
 		if err := val.Commission.ValidateNewRate(newCommissionRate, ctx.BlockHeader().Time); err != nil {
@@ -255,7 +255,7 @@ func SimulateMsgDelegate(ak types.AccountKeeper, bk types.BankKeeper, k *keeper.
 		}
 
 		simAccount, _ := simtypes.RandomAcc(r, accs)
-		val, ok := keeper.RandomValidator(r, k, ctx)
+		val, ok := testutil.RandSliceElem(r, k.GetAllValidators(ctx))
 		if !ok {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgDelegate, "unable to pick a validator"), nil, nil
 		}
@@ -313,14 +313,13 @@ func SimulateMsgUndelegate(ak types.AccountKeeper, bk types.BankKeeper, k *keepe
 	return func(
 		r *rand.Rand, app *baseapp.BaseApp, ctx sdk.Context, accs []simtypes.Account, chainID string,
 	) (simtypes.OperationMsg, []simtypes.FutureOperation, error) {
-		// get random validator
-		validator, ok := keeper.RandomValidator(r, k, ctx)
+		val, ok := testutil.RandSliceElem(r, k.GetAllValidators(ctx))
 		if !ok {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgUndelegate, "validator is not ok"), nil, nil
 		}
 
-		valAddr := validator.GetOperator()
-		delegations := k.GetValidatorDelegations(ctx, validator.GetOperator())
+		valAddr := val.GetOperator()
+		delegations := k.GetValidatorDelegations(ctx, val.GetOperator())
 		if delegations == nil {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgUndelegate, "keeper does have any delegation entries"), nil, nil
 		}
@@ -333,7 +332,7 @@ func SimulateMsgUndelegate(ak types.AccountKeeper, bk types.BankKeeper, k *keepe
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgUndelegate, "keeper does have a max unbonding delegation entries"), nil, nil
 		}
 
-		totalBond := validator.TokensFromShares(delegation.GetShares()).TruncateInt()
+		totalBond := val.TokensFromShares(delegation.GetShares()).TruncateInt()
 		if !totalBond.IsPositive() {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgUndelegate, "total bond is negative"), nil, nil
 		}
@@ -395,19 +394,17 @@ func SimulateMsgCancelUnbondingDelegate(ak types.AccountKeeper, bk types.BankKee
 		if len(k.GetAllValidators(ctx)) == 0 {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgDelegate, "number of validators equal zero"), nil, nil
 		}
-		// get random account
 		simAccount, _ := simtypes.RandomAcc(r, accs)
-		// get random validator
-		validator, ok := keeper.RandomValidator(r, k, ctx)
+		val, ok := testutil.RandSliceElem(r, k.GetAllValidators(ctx))
 		if !ok {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgCancelUnbondingDelegation, "validator is not ok"), nil, nil
 		}
 
-		if validator.IsJailed() || validator.InvalidExRate() {
+		if val.IsJailed() || val.InvalidExRate() {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgCancelUnbondingDelegation, "validator is jailed"), nil, nil
 		}
 
-		valAddr := validator.GetOperator()
+		valAddr := val.GetOperator()
 		unbondingDelegation, found := k.GetUnbondingDelegation(ctx, simAccount.Address, valAddr)
 		if !found {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgCancelUnbondingDelegation, "account does have any unbonding delegation"), nil, nil
@@ -474,8 +471,8 @@ func SimulateMsgBeginRedelegate(ak types.AccountKeeper, bk types.BankKeeper, k *
 	return func(
 		r *rand.Rand, app *baseapp.BaseApp, ctx sdk.Context, accs []simtypes.Account, chainID string,
 	) (simtypes.OperationMsg, []simtypes.FutureOperation, error) {
-		// get random source validator
-		srcVal, ok := keeper.RandomValidator(r, k, ctx)
+		allVals := k.GetAllValidators(ctx)
+		srcVal, ok := testutil.RandSliceElem(r, allVals)
 		if !ok {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgBeginRedelegate, "unable to pick validator"), nil, nil
 		}
@@ -495,7 +492,7 @@ func SimulateMsgBeginRedelegate(ak types.AccountKeeper, bk types.BankKeeper, k *
 		}
 
 		// get random destination validator
-		destVal, ok := keeper.RandomValidator(r, k, ctx)
+		destVal, ok := testutil.RandSliceElem(r, allVals)
 		if !ok {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgBeginRedelegate, "unable to pick validator"), nil, nil
 		}