rpc: make getnextvalidators behavior compliant with C# node

Turns out, our getnextvalidators implementation already works the way
getcandidates is supposed to work, but original getnextvalidators works a bit
differently. It only returns validators, it doesn't return Active flag (all
of them are active) and it represents votes as a number. So for the maximum
compatibility:
 * drop non-validator keys from getnextvalidators server-side
 * drop Active flag client-side (sorry, it doesn't exist)
 * allow unmarshalling old answers along with the new one

This technically breaks `query candidates` CLI command, but it'll be fixed
when getcandidates are to be introduced.

cli/query/query.go

@@ -177,19 +177,21 @@ func queryCandidates(ctx *cli.Context) error {
 	}
 
 	sort.Slice(vals, func(i, j int) bool {
-		if vals[i].Active != vals[j].Active {
-			return vals[i].Active
-		}
-		if vals[i].Votes != vals[j].Votes {
-			return vals[i].Votes > vals[j].Votes
-		}
+		/*
+			if vals[i].Active != vals[j].Active {
+				return vals[i].Active
+			}
+			if vals[i].Votes != vals[j].Votes {
+				return vals[i].Votes > vals[j].Votes
+			}
+		*/
 		return vals[i].PublicKey.Cmp(&vals[j].PublicKey) == -1
 	})
 	buf := bytes.NewBuffer(nil)
 	tw := tabwriter.NewWriter(buf, 0, 2, 2, ' ', 0)
 	_, _ = tw.Write([]byte("Key\tVotes\tCommittee\tConsensus\n"))
 	for _, val := range vals {
-		_, _ = tw.Write([]byte(fmt.Sprintf("%s\t%d\t%t\t%t\n", hex.EncodeToString(val.PublicKey.Bytes()), val.Votes, comm.Contains(&val.PublicKey), val.Active)))
+		_, _ = tw.Write([]byte(fmt.Sprintf("%s\t%d\t%t\t%t\n", hex.EncodeToString(val.PublicKey.Bytes()), val.Votes, comm.Contains(&val.PublicKey), true)))
 	}
 	_ = tw.Flush()
 	fmt.Fprint(ctx.App.Writer, buf.String())

pkg/rpc/client/rpc.go

@@ -557,7 +557,7 @@ func (c *Client) GetUnclaimedGas(address string) (result.UnclaimedGas, error) {
 	return resp, nil
 }
 
-// GetNextBlockValidators returns the current NEO consensus nodes information and voting status.
+// GetNextBlockValidators returns the current NEO consensus nodes information and voting data.
 func (c *Client) GetNextBlockValidators() ([]result.Validator, error) {
 	var (
 		params = request.NewRawParams()

pkg/rpc/response/result/validator.go

@@ -1,13 +1,43 @@
 package result
 
 import (
+	"encoding/json"
+
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
 )
 
-// Validator used for the representation of
-// state.Validator on the RPC Server.
+// Validator is used for the representation of consensus node data in the JSON-RPC
+// protocol.
 type Validator struct {
 	PublicKey keys.PublicKey `json:"publickey"`
-	Votes     int64          `json:"votes,string"`
-	Active    bool           `json:"active"`
+	Votes     int64          `json:"votes"`
+}
+
+type newValidator struct {
+	PublicKey keys.PublicKey `json:"publickey"`
+	Votes     int64          `json:"votes"`
+}
+
+type oldValidator struct {
+	PublicKey keys.PublicKey `json:"publickey"`
+	Votes     int64          `json:"votes,string"`
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface.
+func (v *Validator) UnmarshalJSON(data []byte) error {
+	var nv = new(newValidator)
+	err := json.Unmarshal(data, nv)
+	if err != nil {
+		var ov = new(oldValidator)
+		err := json.Unmarshal(data, ov)
+		if err != nil {
+			return err
+		}
+		v.PublicKey = ov.PublicKey
+		v.Votes = ov.Votes
+		return nil
+	}
+	v.PublicKey = nv.PublicKey
+	v.Votes = nv.Votes
+	return nil
 }

pkg/rpc/response/result/validator_test.go

@@ -0,0 +1,22 @@
+package result
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestValidatorUnmarshal(t *testing.T) {
+	old := []byte(`{"publickey":"02a7bc55fe8684e0119768d104ba30795bdcc86619e864add26156723ed185cd62","votes":"100500","active":true}`)
+	v := new(Validator)
+	require.NoError(t, json.Unmarshal(old, v))
+	require.Equal(t, int64(100500), v.Votes)
+
+	new := []byte(`{"publickey":"02a7bc55fe8684e0119768d104ba30795bdcc86619e864add26156723ed185cd62","votes":42}`)
+	require.NoError(t, json.Unmarshal(new, v))
+	require.Equal(t, int64(42), v.Votes)
+
+	bad := []byte(`{"publickey":"02a7bc55fe8684e0119768d104ba30795bdcc86619e864add26156723ed185cd62","votes":"notanumber"}`)
+	require.Error(t, json.Unmarshal(bad, v))
+}

pkg/rpc/server/server.go

@@ -1552,10 +1552,12 @@ func (s *Server) getNextBlockValidators(_ request.Params) (interface{}, *respons
 	}
 	var res = make([]result.Validator, 0)
 	for _, v := range enrollments {
+		if !validators.Contains(v.Key) {
+			continue
+		}
 		res = append(res, result.Validator{
 			PublicKey: *v.Key,
 			Votes:     v.Votes.Int64(),
-			Active:    validators.Contains(v.Key),
 		})
 	}
 	return res, nil