feat(x/gov): add MaxVoteOptionsLen

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 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/config.go

@@ -26,6 +26,8 @@ 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
+	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 +39,7 @@ func DefaultConfig() Config {
 		MaxTitleLen:                          255,
 		MaxMetadataLen:                       255,
 		MaxSummaryLen:                        10200,
+		MaxVoteOptionsLen:                    0, // means all supported options
 		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.
+	if config.MaxVoteOptionsLen == 0 {
+		config.MaxVoteOptionsLen = defaultConfig.MaxVoteOptionsLen
+	}
 
 	sb := collections.NewSchemaBuilder(env.KVStoreService)
 	k := &Keeper{
@@ -230,3 +234,12 @@ 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.
+func (k Keeper) assertVoteOptionsLen(options v1.WeightedVoteOptions) error {
+	if uint64(len(options)) > k.config.MaxVoteOptionsLen {
+		return types.ErrTooManyVoteOptions.Wrapf("got %d 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:

x/gov/proto/cosmos/gov/module/v1/module.proto

@@ -24,4 +24,8 @@ message Module {
   // max_summary_len defines the maximum proposal summary length.
   // Defaults to 10200 if not explicitly set.
   uint64 max_summary_len = 4;
+
+  // max_vote_options_len defines the maximum number of vote options a proposal can have.
+  // Defaults to 0 if not explicitly set.
+  uint64 max_vote_options_len = 5;
 }

x/gov/types/errors.go

@@ -27,4 +27,5 @@ var (
 	ErrInvalidDepositDenom     = errors.Register(ModuleName, 23, "invalid deposit denom")
 	ErrTitleTooLong            = errors.Register(ModuleName, 24, "title too long")
 	ErrTooLateToCancel         = errors.Register(ModuleName, 25, "too late to cancel proposal")
+	ErrTooManyVoteOptions      = errors.Register(ModuleName, 26, "too many vote options")
 )