fixup! fix(drand): add null HistoricalBeaconClient for old beacons

chain/beacon/drand/drand.go

@@ -102,9 +102,6 @@ func NewDrandBeacon(genesisTs, interval uint64, ps *pubsub.PubSub, config dtypes
 		hc.(DrandHTTPClient).SetUserAgent("drand-client-lotus/" + build.NodeBuildVersion)
 		clients = append(clients, hc)
 	}
-	if len(clients) == 0 {
-		clients = append(clients, HistoricalBeaconClient{})
-	}
 
 	opts := []dclient.Option{
 		dclient.WithChainInfo(drandChain),
@@ -116,6 +113,13 @@ func NewDrandBeacon(genesisTs, interval uint64, ps *pubsub.PubSub, config dtypes
 		opts = append(opts, gclient.WithPubsub(ps))
 	} else {
 		log.Info("drand beacon without pubsub")
+		if len(clients) == 0 {
+			historicalClient := &historicalBeaconClient{}
+			clients = append(clients, historicalClient)
+			opts = append(opts, dclient.WithWatcher(func(chainInfo *dchain.Info, cache dclient.Cache) (dclient.Watcher, error) {
+				return historicalClient, nil
+			}))
+		}
 	}
 
 	client, err := dclient.Wrap(clients, opts...)
@@ -254,30 +258,30 @@ func BeaconScheduleFromDrandSchedule(dcs dtypes.DrandSchedule, genesisTime uint6
 	return shd, nil
 }
 
-var _ dclient.Client = HistoricalBeaconClient{}
+var _ dclient.Client = historicalBeaconClient{}
 
-// HistoricalBeaconClient is a drand client that doesn't actually do anything. It's used when
+// historicalBeaconClient is a drand client that doesn't actually do anything. It's used when
 // we don't have a drand network to connect to but still need to provide a beacon client.
 // We don't expect calls through to the client to be made since we should only be verifying old
 // randomness, not fetching it.
-type HistoricalBeaconClient struct{}
+type historicalBeaconClient struct{}
 
-func (h HistoricalBeaconClient) Get(ctx context.Context, round uint64) (dclient.Result, error) {
+func (h historicalBeaconClient) Get(ctx context.Context, round uint64) (dclient.Result, error) {
 	return nil, xerrors.Errorf("no historical randomness available")
 }
 
-func (h HistoricalBeaconClient) Watch(ctx context.Context) <-chan dclient.Result {
+func (h historicalBeaconClient) Watch(ctx context.Context) <-chan dclient.Result {
 	return nil
 }
 
-func (h HistoricalBeaconClient) Info(ctx context.Context) (*dchain.Info, error) {
+func (h historicalBeaconClient) Info(ctx context.Context) (*dchain.Info, error) {
 	return nil, xerrors.Errorf("no historical randomness available")
 }
 
-func (h HistoricalBeaconClient) RoundAt(time.Time) uint64 {
+func (h historicalBeaconClient) RoundAt(time.Time) uint64 {
 	return 0
 }
 
-func (h HistoricalBeaconClient) Close() error {
+func (h historicalBeaconClient) Close() error {
 	return nil
 }