blockchain: Reject params with blank choice id.

This adds an additional validation check to the chain initialization
process to validate that none of the IDs of the choices in the given
chain params are blank.

It also adds a test for the new validation logic.

internal/blockchain/chain.go

@@ -2031,6 +2031,13 @@ func validateDeploymentChoices(voteParams *chaincfg.Vote) error {
 	var numAbstain, numNo int
 	dups := make(map[string]int)
 	for choiceIdx, choice := range voteParams.Choices {
+		// Ensure the id is not empty.
+		if choice.Id == "" {
+			str := fmt.Sprintf("deployment ID %s choice index %d does not "+
+				"have an ID", voteParams.Id, choiceIdx)
+			return contextError(ErrDeploymentMissingChoiceID, str)
+		}
+
 		// Ensure that the choice bits are not zero for all choices except the
 		// abstain choice.
 		if choice.Bits == 0 && !choice.IsAbstain {

internal/blockchain/chain_test.go

@@ -189,6 +189,13 @@ func TestDeploymentParamsValidation(t *testing.T) {
 			})
 		},
 		err: ErrDeploymentTooManyChoices,
+	}, {
+		name: "reject choices without an id",
+		munger: func(params *chaincfg.Params) {
+			vote := &params.Deployments[0][0].Vote
+			vote.Choices[1].Id = ""
+		},
+		err: ErrDeploymentMissingChoiceID,
 	}, {
 		name: "reject choice with abstain bits but no abstain flag",
 		munger: func(params *chaincfg.Params) {

internal/blockchain/error.go

@@ -654,6 +654,9 @@ const (
 	// a deployment that its mask can represent.
 	ErrDeploymentTooManyChoices = ErrorKind("ErrDeploymentTooManyChoices")
 
+	// ErrDeploymentMissingChoiceID indicates a choice id is not set.
+	ErrDeploymentMissingChoiceID = ErrorKind("ErrDeploymentMissingChoiceID")
+
 	// ErrDeploymentBadChoiceBits indicates the choice bits that represent a
 	// deployment vote choice are invalid in some way.  For example, when they
 	// are all zero and the choice is not also marked as abstain or they are not

internal/blockchain/error_test.go

@@ -163,6 +163,7 @@ func TestErrorKindStringer(t *testing.T) {
 		{ErrUnknownDeploymentChoice, "ErrUnknownDeploymentChoice"},
 		{ErrDeploymentBadMask, "ErrDeploymentBadMask"},
 		{ErrDeploymentTooManyChoices, "ErrDeploymentTooManyChoices"},
+		{ErrDeploymentMissingChoiceID, "ErrDeploymentMissingChoiceID"},
 		{ErrDeploymentBadChoiceBits, "ErrDeploymentBadChoiceBits"},
 		{ErrDeploymentNonExclusiveFlags, "ErrDeploymentNonExclusiveFlags"},
 		{ErrDeploymentDuplicateChoice, "ErrDeploymentDuplicateChoice"},