core/bloombits, eth/filters: handle null topics (#15195)

When implementing the new bloombits based filter, I've accidentally broke null
topics by removing the special casing of common.Hash{} filter rules, which
acted as the wildcard topic until now.

This PR fixes the regression, but instead of using the magic hash
common.Hash{} as the null wildcard, the PR reworks the code to handle nil
topics during parsing, converting a JSON null into nil []common.Hash topic.

1 files changed, 7 insertions, 15 deletions

diff --git a/eth/filters/filter.go b/eth/filters/filter.go
index 4f6c30058..026cbf95c 100644
--- a/eth/filters/filter.go
+++ b/eth/filters/filter.go
@@ -60,7 +60,9 @@ type Filter struct {
 // New creates a new filter which uses a bloom filter on blocks to figure out whether
 // a particular block is interesting or not.
 func New(backend Backend, begin, end int64, addresses []common.Address, topics [][]common.Hash) *Filter {
-	// Flatten the address and topic filter clauses into a single filter system
+	// Flatten the address and topic filter clauses into a single bloombits filter
+	// system. Since the bloombits are not positional, nil topics are permitted,
+	// which get flattened into a nil byte slice.
 	var filters [][][]byte
 	if len(addresses) > 0 {
 		filter := make([][]byte, len(addresses))
@@ -235,32 +237,24 @@ Logs:
 		if len(addresses) > 0 && !includes(addresses, log.Address) {
 			continue
 		}
-
-		logTopics := make([]common.Hash, len(topics))
-		copy(logTopics, log.Topics)
-
 		// If the to filtered topics is greater than the amount of topics in logs, skip.
 		if len(topics) > len(log.Topics) {
 			continue Logs
 		}
-
 		for i, topics := range topics {
-			var match bool
+			match := len(topics) == 0 // empty rule set == wildcard
 			for _, topic := range topics {
-				// common.Hash{} is a match all (wildcard)
-				if (topic == common.Hash{}) || log.Topics[i] == topic {
+				if log.Topics[i] == topic {
 					match = true
 					break
 				}
 			}
-
 			if !match {
 				continue Logs
 			}
 		}
 		ret = append(ret, log)
 	}
-
 	return ret
 }
 
@@ -273,16 +267,15 @@ func bloomFilter(bloom types.Bloom, addresses []common.Address, topics [][]commo
 				break
 			}
 		}
-
 		if !included {
 			return false
 		}
 	}
 
 	for _, sub := range topics {
-		var included bool
+		included := len(sub) == 0 // empty rule set == wildcard
 		for _, topic := range sub {
-			if (topic == common.Hash{}) || types.BloomLookup(bloom, topic) {
+			if types.BloomLookup(bloom, topic) {
 				included = true
 				break
 			}
@@ -291,6 +284,5 @@ func bloomFilter(bloom types.Bloom, addresses []common.Address, topics [][]commo
 			return false
 		}
 	}
-
 	return true
 }