ethclient: Fix eth_getBlockReceipts call when using block numbers or labels

The String() version of BlockNumberOrHash uses decimal for all block numbers, including negative ones used to indicate labels. Switch to using BlockNumber.String() which encodes it correctly for use in the JSON-RPC API.

rpc/types.go

@@ -21,7 +21,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"math"
-	"strconv"
 	"strings"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -221,7 +220,7 @@ func (bnh *BlockNumberOrHash) Number() (BlockNumber, bool) {
 
 func (bnh *BlockNumberOrHash) String() string {
 	if bnh.BlockNumber != nil {
-		return strconv.Itoa(int(*bnh.BlockNumber))
+		return bnh.BlockNumber.String()
 	}
 	if bnh.BlockHash != nil {
 		return bnh.BlockHash.String()

rpc/types_test.go

@@ -153,3 +153,33 @@ func TestBlockNumberOrHash_WithNumber_MarshalAndUnmarshal(t *testing.T) {
 		})
 	}
 }
+
+func TestBlockNumberOrHash_WithNumber_StringAndUnmarshal(t *testing.T) {
+	tests := []struct {
+		name  string
+		value BlockNumberOrHash
+	}{
+		{"max", BlockNumberOrHashWithNumber(math.MaxInt64)},
+		{"pending", BlockNumberOrHashWithNumber(PendingBlockNumber)},
+		{"latest", BlockNumberOrHashWithNumber(LatestBlockNumber)},
+		{"earliest", BlockNumberOrHashWithNumber(EarliestBlockNumber)},
+		{"0x20", BlockNumberOrHashWithNumber(32)},
+		{"hash", BlockNumberOrHashWithHash(common.Hash{0xaa}, false)},
+	}
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			bnh := test.value
+			// Wrap the string value in quotes to make it a JSON string.
+			marshalled := []byte("\"" + bnh.String() + "\"")
+			var unmarshalled BlockNumberOrHash
+			err := json.Unmarshal(marshalled, &unmarshalled)
+			if err != nil {
+				t.Fatalf("cannot unmarshal (%v): %v", string(marshalled), err)
+			}
+			if !reflect.DeepEqual(bnh, unmarshalled) {
+				t.Fatalf("wrong result: expected %v, got %v", bnh, unmarshalled)
+			}
+		})
+	}
+}