eth/filter: add support for pending logs (#3219)

eth/filters/api.go

@@ -239,11 +239,17 @@ func (api *PublicFilterAPI) Logs(ctx context.Context, crit FilterCriteria) (*rpc
 		return &rpc.Subscription{}, rpc.ErrNotificationsUnsupported
 	}
 
-	rpcSub := notifier.CreateSubscription()
+	var (
+		rpcSub      = notifier.CreateSubscription()
+		matchedLogs = make(chan []Log)
+	)
+
+	logsSub, err := api.events.SubscribeLogs(crit, matchedLogs)
+	if err != nil {
+		return nil, err
+	}
 
 	go func() {
-		matchedLogs := make(chan []Log)
-		logsSub := api.events.SubscribeLogs(crit, matchedLogs)
 
 		for {
 			select {
@@ -276,18 +282,20 @@ type FilterCriteria struct {
 // used to retrieve logs when the state changes. This method cannot be
 // used to fetch logs that are already stored in the state.
 //
+// Default criteria for the from and to block are "latest".
+// Using "latest" as block number will return logs for mined blocks.
+// Using "pending" as block number returns logs for not yet mined (pending) blocks.
+// In case logs are removed (chain reorg) previously returned logs are returned
+// again but with the removed property set to true.
+//
+// In case "fromBlock" > "toBlock" an error is returned.
+//
 // https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_newfilter
-func (api *PublicFilterAPI) NewFilter(crit FilterCriteria) rpc.ID {
-	var (
-		logs    = make(chan []Log)
-		logsSub = api.events.SubscribeLogs(crit, logs)
-	)
-
-	if crit.FromBlock == nil {
-		crit.FromBlock = big.NewInt(rpc.LatestBlockNumber.Int64())
-	}
-	if crit.ToBlock == nil {
-		crit.ToBlock = big.NewInt(rpc.LatestBlockNumber.Int64())
+func (api *PublicFilterAPI) NewFilter(crit FilterCriteria) (rpc.ID, error) {
+	logs := make(chan []Log)
+	logsSub, err := api.events.SubscribeLogs(crit, logs)
+	if err != nil {
+		return rpc.ID(""), err
 	}
 
 	api.filtersMu.Lock()
@@ -312,7 +320,7 @@ func (api *PublicFilterAPI) NewFilter(crit FilterCriteria) rpc.ID {
 		}
 	}()
 
-	return logsSub.ID
+	return logsSub.ID, nil
 }
 
 // GetLogs returns logs matching the given argument that are stored within the state.
@@ -363,28 +371,38 @@ func (api *PublicFilterAPI) GetFilterLogs(ctx context.Context, id rpc.ID) ([]Log
 	api.filtersMu.Unlock()
 
 	if !found || f.typ != LogsSubscription {
-		return []Log{}, nil
+		return nil, fmt.Errorf("filter not found")
 	}
 
 	filter := New(api.backend, api.useMipMap)
-	filter.SetBeginBlock(f.crit.FromBlock.Int64())
-	filter.SetEndBlock(f.crit.ToBlock.Int64())
+	if f.crit.FromBlock != nil {
+		filter.SetBeginBlock(f.crit.FromBlock.Int64())
+	} else {
+		filter.SetBeginBlock(rpc.LatestBlockNumber.Int64())
+	}
+	if f.crit.ToBlock != nil {
+		filter.SetEndBlock(f.crit.ToBlock.Int64())
+	} else {
+		filter.SetEndBlock(rpc.LatestBlockNumber.Int64())
+	}
 	filter.SetAddresses(f.crit.Addresses)
 	filter.SetTopics(f.crit.Topics)
 
-	logs, err := filter.Find(ctx)
-	return returnLogs(logs), err
+	logs, err:= filter.Find(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return returnLogs(logs), nil
 }
 
 // GetFilterChanges returns the logs for the filter with the given id since
 // last time is was called. This can be used for polling.
 //
 // For pending transaction and block filters the result is []common.Hash.
-// (pending)Log filters return []Log. If the filter could not be found
-// []interface{}{} is returned.
+// (pending)Log filters return []Log.
 //
 // https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_getfilterchanges
-func (api *PublicFilterAPI) GetFilterChanges(id rpc.ID) interface{} {
+func (api *PublicFilterAPI) GetFilterChanges(id rpc.ID) (interface{}, error) {
 	api.filtersMu.Lock()
 	defer api.filtersMu.Unlock()
 
@@ -400,15 +418,15 @@ func (api *PublicFilterAPI) GetFilterChanges(id rpc.ID) interface{} {
 		case PendingTransactionsSubscription, BlocksSubscription:
 			hashes := f.hashes
 			f.hashes = nil
-			return returnHashes(hashes)
-		case PendingLogsSubscription, LogsSubscription:
+			return returnHashes(hashes), nil
+		case LogsSubscription:
 			logs := f.logs
 			f.logs = nil
-			return returnLogs(logs)
+			return returnLogs(logs), nil
 		}
 	}
 
-	return []interface{}{}
+	return []interface{}{}, fmt.Errorf("filter not found")
 }
 
 // returnHashes is a helper that will return an empty hash array case the given hash array is nil,
@@ -443,15 +461,11 @@ func (args *FilterCriteria) UnmarshalJSON(data []byte) error {
 		return err
 	}
 
-	if raw.From == nil || raw.From.Int64() < 0 {
-		args.FromBlock = big.NewInt(rpc.LatestBlockNumber.Int64())
-	} else {
+	if raw.From != nil {
 		args.FromBlock = big.NewInt(raw.From.Int64())
 	}
 
-	if raw.ToBlock == nil || raw.ToBlock.Int64() < 0 {
-		args.ToBlock = big.NewInt(rpc.LatestBlockNumber.Int64())
-	} else {
+	if raw.ToBlock != nil {
 		args.ToBlock = big.NewInt(raw.ToBlock.Int64())
 	}