feat(x/gov): add MaxVoteOptionsLen (cosmos#20087)

x/gov/CHANGELOG.md

@@ -27,6 +27,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Features
 
+* [#20087](https://github.com/cosmos/cosmos-sdk/pull/20087) add `MaxVoteOptionsLen`
 * [#19592](https://github.com/cosmos/cosmos-sdk/pull/19592) Add custom tally function.
 * [#19304](https://github.com/cosmos/cosmos-sdk/pull/19304) Add `MsgSudoExec` for allowing executing any message as a sudo.
 * [#19101](https://github.com/cosmos/cosmos-sdk/pull/19101) Add message based params configuration.

x/gov/README.md

@@ -183,6 +183,8 @@ https://github.com/cosmos/cosmos-sdk/blob/v0.47.0-rc1/proto/cosmos/gov/v1beta1/g
 
 For a weighted vote to be valid, the `options` field must not contain duplicate vote options, and the sum of weights of all options must be equal to 1.
 
+The maximum number of weighted vote options can be limited by the developer via a config parameter, named `MaxVoteOptionsLen`, which gets passed into the gov keeper.
+
 ### Quorum
 
 Quorum is defined as the minimum percentage of voting power that needs to be

x/gov/keeper/common_test.go

@@ -166,6 +166,75 @@ func setupGovKeeper(t *testing.T, expectations ...func(sdk.Context, mocks)) (
 	return govKeeper, m, encCfg, ctx
 }
 
+// setupGovKeeperWithMaxVoteOptionsLen creates a govKeeper with a defined maxVoteOptionsLen, as well as all its dependencies.
+func setupGovKeeperWithMaxVoteOptionsLen(t *testing.T, maxVoteOptionsLen uint64, expectations ...func(sdk.Context, mocks)) (
+	*keeper.Keeper,
+	mocks,
+	moduletestutil.TestEncodingConfig,
+	sdk.Context,
+) {
+	t.Helper()
+	key := storetypes.NewKVStoreKey(types.StoreKey)
+	storeService := runtime.NewKVStoreService(key)
+	testCtx := testutil.DefaultContextWithDB(t, key, storetypes.NewTransientStoreKey("transient_test"))
+	ctx := testCtx.Ctx.WithHeaderInfo(header.Info{Time: time.Now()})
+	encCfg := moduletestutil.MakeTestEncodingConfig(codectestutil.CodecOptions{})
+	v1.RegisterInterfaces(encCfg.InterfaceRegistry)
+	v1beta1.RegisterInterfaces(encCfg.InterfaceRegistry)
+	banktypes.RegisterInterfaces(encCfg.InterfaceRegistry)
+
+	baseApp := baseapp.NewBaseApp(
+		"authz",
+		log.NewNopLogger(),
+		testCtx.DB,
+		encCfg.TxConfig.TxDecoder(),
+	)
+	baseApp.SetCMS(testCtx.CMS)
+	baseApp.SetInterfaceRegistry(encCfg.InterfaceRegistry)
+
+	environment := runtime.NewEnvironment(storeService, log.NewNopLogger(), runtime.EnvWithRouterService(baseApp.GRPCQueryRouter(), baseApp.MsgServiceRouter()))
+
+	// gomock initializations
+	ctrl := gomock.NewController(t)
+	m := mocks{
+		acctKeeper:    govtestutil.NewMockAccountKeeper(ctrl),
+		bankKeeper:    govtestutil.NewMockBankKeeper(ctrl),
+		stakingKeeper: govtestutil.NewMockStakingKeeper(ctrl),
+		poolKeeper:    govtestutil.NewMockPoolKeeper(ctrl),
+	}
+	if len(expectations) == 0 {
+		err := mockDefaultExpectations(ctx, m)
+		require.NoError(t, err)
+	} else {
+		for _, exp := range expectations {
+			exp(ctx, m)
+		}
+	}
+
+	govAddr, err := m.acctKeeper.AddressCodec().BytesToString(govAcct)
+	require.NoError(t, err)
+
+	config := keeper.DefaultConfig()
+	config.MaxVoteOptionsLen = maxVoteOptionsLen
+
+	// Gov keeper initializations
+	govKeeper := keeper.NewKeeper(encCfg.Codec, environment, m.acctKeeper, m.bankKeeper, m.stakingKeeper, m.poolKeeper, config, govAddr)
+	require.NoError(t, govKeeper.ProposalID.Set(ctx, 1))
+	govRouter := v1beta1.NewRouter() // Also register legacy gov handlers to test them too.
+	govRouter.AddRoute(types.RouterKey, v1beta1.ProposalHandler)
+	govKeeper.SetLegacyRouter(govRouter)
+	err = govKeeper.Params.Set(ctx, v1.DefaultParams())
+	require.NoError(t, err)
+	err = govKeeper.Constitution.Set(ctx, "constitution")
+	require.NoError(t, err)
+
+	// Register all handlers for the MegServiceRouter.
+	v1.RegisterMsgServer(baseApp.MsgServiceRouter(), keeper.NewMsgServerImpl(govKeeper))
+	banktypes.RegisterMsgServer(baseApp.MsgServiceRouter(), nil) // Nil is fine here as long as we never execute the proposal's Msgs.
+
+	return govKeeper, m, encCfg, ctx
+}
+
 // trackMockBalances sets up expected calls on the Mock BankKeeper, and also
 // locally tracks accounts balances (not modules balances).
 func trackMockBalances(bankKeeper *govtestutil.MockBankKeeper) error {

x/gov/keeper/config.go

@@ -26,6 +26,10 @@ type Config struct {
 	MaxMetadataLen uint64
 	// MaxSummaryLen defines the amount of characters that can be used for proposal summary
 	MaxSummaryLen uint64
+	// MaxVoteOptionsLen defines the maximum number of vote options a proposal can have.
+	// This only applies to WeightedVoteOption messages and not to the VoteOption messages
+	// 0 means this param is disabled, hence all supported options are allowed
+	MaxVoteOptionsLen uint64
 	// CalculateVoteResultsAndVotingPowerFn is a function signature for calculating vote results and voting power
 	// Keeping it nil will use the default implementation
 	CalculateVoteResultsAndVotingPowerFn CalculateVoteResultsAndVotingPowerFn
@@ -37,6 +41,7 @@ func DefaultConfig() Config {
 		MaxTitleLen:                          255,
 		MaxMetadataLen:                       255,
 		MaxSummaryLen:                        10200,
+		MaxVoteOptionsLen:                    0, // 0 means this param is disabled, hence all supported options are allowed
 		CalculateVoteResultsAndVotingPowerFn: nil,
 	}
 }

x/gov/keeper/keeper.go

@@ -106,6 +106,10 @@ func NewKeeper(
 	if config.MaxSummaryLen == 0 {
 		config.MaxSummaryLen = defaultConfig.MaxSummaryLen
 	}
+	// If MaxVoteOptionsLen not set by app developer, set to default value, meaning all supported options are allowed
+	if config.MaxVoteOptionsLen == 0 {
+		config.MaxVoteOptionsLen = defaultConfig.MaxVoteOptionsLen
+	}
 
 	sb := collections.NewSchemaBuilder(env.KVStoreService)
 	k := &Keeper{
@@ -230,3 +234,14 @@ func (k Keeper) assertSummaryLength(summary string) error {
 	}
 	return nil
 }
+
+// assertVoteOptionsLen returns an error if given vote options length
+// is greater than a pre-defined MaxVoteOptionsLen.
+// It's only being checked when config.MaxVoteOptionsLen > 0 (param enabled)
+func (k Keeper) assertVoteOptionsLen(options v1.WeightedVoteOptions) error {
+	maxVoteOptionsLen := k.config.MaxVoteOptionsLen
+	if maxVoteOptionsLen > 0 && uint64(len(options)) > maxVoteOptionsLen {
+		return types.ErrTooManyVoteOptions.Wrapf("got %d weighted vote options, maximum allowed is %d", len(options), k.config.MaxVoteOptionsLen)
+	}
+	return nil
+}

x/gov/keeper/vote.go

@@ -35,6 +35,11 @@ func (k Keeper) AddVote(ctx context.Context, proposalID uint64, voterAddr sdk.Ac
 		return err
 	}
 
+	err = k.assertVoteOptionsLen(options)
+	if err != nil {
+		return err
+	}
+
 	for _, option := range options {
 		switch proposal.ProposalType {
 		case v1.ProposalType_PROPOSAL_TYPE_OPTIMISTIC: