rpc: simplify the encoding of interface-typed arguments in JSON (#7600)

Add package jsontypes that implements a subset of the custom libs/json 
package. Specifically it handles encoding and decoding of interface types
wrapped in "tagged" JSON objects. It omits the deep reflection on arbitrary
types, preserving only the handling of type tags wrapper encoding.

- Register interface types (Evidence, PubKey, PrivKey) for tagged encoding.
- Update the existing implementations to satisfy the type.
- Register those types with the jsontypes registry.
- Add string tags to 64-bit integer fields where needed.
- Add marshalers to structs that export interface-typed fields.

types/evidence.go

@@ -13,6 +13,7 @@ import (
 	abci "github.com/tendermint/tendermint/abci/types"
 	"github.com/tendermint/tendermint/crypto/merkle"
 	"github.com/tendermint/tendermint/crypto/tmhash"
+	"github.com/tendermint/tendermint/internal/jsontypes"
 	tmjson "github.com/tendermint/tendermint/libs/json"
 	tmrand "github.com/tendermint/tendermint/libs/rand"
 	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
@@ -28,6 +29,9 @@ type Evidence interface {
 	String() string        // string format of the evidence
 	Time() time.Time       // time of the infraction
 	ValidateBasic() error  // basic consistency check
+
+	// Implementations must support tagged encoding in JSON.
+	jsontypes.Tagged
 }
 
 //--------------------------------------------------------------------------------------
@@ -38,11 +42,14 @@ type DuplicateVoteEvidence struct {
 	VoteB *Vote `json:"vote_b"`
 
 	// abci specific information
-	TotalVotingPower int64
-	ValidatorPower   int64
+	TotalVotingPower int64 `json:",string"`
+	ValidatorPower   int64 `json:",string"`
 	Timestamp        time.Time
 }
 
+// TypeTag implements the jsontypes.Tagged interface.
+func (*DuplicateVoteEvidence) TypeTag() string { return "tendermint/DuplicateVoteEvidence" }
+
 var _ Evidence = &DuplicateVoteEvidence{}
 
 // NewDuplicateVoteEvidence creates DuplicateVoteEvidence with right ordering given
@@ -236,14 +243,17 @@ func DuplicateVoteEvidenceFromProto(pb *tmproto.DuplicateVoteEvidence) (*Duplica
 // height, then nodes will treat this as of the Lunatic form, else it is of the Equivocation form.
 type LightClientAttackEvidence struct {
 	ConflictingBlock *LightBlock
-	CommonHeight     int64
+	CommonHeight     int64 `json:",string"`
 
 	// abci specific information
 	ByzantineValidators []*Validator // validators in the validator set that misbehaved in creating the conflicting block
-	TotalVotingPower    int64        // total voting power of the validator set at the common height
+	TotalVotingPower    int64        `json:",string"` // total voting power of the validator set at the common height
 	Timestamp           time.Time    // timestamp of the block at the common height
 }
 
+// TypeTag implements the jsontypes.Tagged interface.
+func (*LightClientAttackEvidence) TypeTag() string { return "tendermint/LightClientAttackEvidence" }
+
 var _ Evidence = &LightClientAttackEvidence{}
 
 // ABCI forms an array of abci evidence for each byzantine validator
@@ -365,10 +375,10 @@ func (l *LightClientAttackEvidence) Height() int64 {
 // String returns a string representation of LightClientAttackEvidence
 func (l *LightClientAttackEvidence) String() string {
 	return fmt.Sprintf(`LightClientAttackEvidence{
-		ConflictingBlock: %v, 
-		CommonHeight: %d, 
-		ByzatineValidators: %v, 
-		TotalVotingPower: %d, 
+		ConflictingBlock: %v,
+		CommonHeight: %d,
+		ByzatineValidators: %v,
+		TotalVotingPower: %d,
 		Timestamp: %v}#%X`,
 		l.ConflictingBlock.String(), l.CommonHeight, l.ByzantineValidators,
 		l.TotalVotingPower, l.Timestamp, l.Hash())
@@ -630,6 +640,9 @@ func EvidenceFromProto(evidence *tmproto.Evidence) (Evidence, error) {
 func init() {
 	tmjson.RegisterType(&DuplicateVoteEvidence{}, "tendermint/DuplicateVoteEvidence")
 	tmjson.RegisterType(&LightClientAttackEvidence{}, "tendermint/LightClientAttackEvidence")
+
+	jsontypes.MustRegister((*DuplicateVoteEvidence)(nil))
+	jsontypes.MustRegister((*LightClientAttackEvidence)(nil))
 }
 
 //-------------------------------------------- ERRORS --------------------------------------