fix: cleanup unused cancel function in filter (#452)

* fix: cleanup unused cancel function in filter

* doc

* test

---------

Co-authored-by: Vlad J <vladjdk@gmail.com>

Author: mmsqe

CHANGELOG.md

@@ -22,6 +22,7 @@
 - [\#376](https://github.com/cosmos/evm/pull/376) Fix precompile initialization for local node development script
 - [\#384](https://github.com/cosmos/evm/pull/384) Fix debug_traceTransaction RPC failing with block height mismatch errors
 - [\#441](https://github.com/cosmos/evm/pull/441) Align precompiles map with available static check to Prague.
+- [\#452](https://github.com/cosmos/evm/pull/452) Cleanup unused cancel function in filter.
 - [\#454](https://github.com/cosmos/evm/pull/454) Align multi decode functions instead of string contains check in HexAddressFromBech32String.
 
 ### IMPROVEMENTS

rpc/namespaces/ethereum/eth/filters/api.go

@@ -65,7 +65,6 @@ type filter struct {
 	typ      filters.Type
 	deadline *time.Timer // filter is inactive when deadline triggers
 	crit     filters.FilterCriteria
-	cancel   context.CancelFunc
 	offset   int // offset for stream subscription
 }
 
@@ -128,7 +127,6 @@ func (api *PublicFilterAPI) timeoutLoop() {
 		for id, f := range api.filters {
 			select {
 			case <-f.deadline.C:
-				f.cancel()
 				delete(api.filters, id)
 			default:
 				continue

rpc/namespaces/ethereum/eth/filters/api_test.go

@@ -0,0 +1,40 @@
+package filters
+
+import (
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/ethereum/go-ethereum/eth/filters"
+	"github.com/ethereum/go-ethereum/rpc"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTimeoutLoop_PanicOnNilCancel(t *testing.T) {
+	api := &PublicFilterAPI{
+		filters:   make(map[rpc.ID]*filter),
+		filtersMu: sync.Mutex{},
+		deadline:  10 * time.Millisecond,
+	}
+	api.filters[rpc.NewID()] = &filter{
+		typ:      filters.BlocksSubscription,
+		deadline: time.NewTimer(0),
+	}
+	done := make(chan struct{})
+	go func() {
+		defer func() {
+			if r := recover(); r == nil {
+				t.Errorf("cancel panic")
+			}
+			close(done)
+		}()
+		api.timeoutLoop()
+	}()
+	panicked := false
+	select {
+	case <-done:
+		panicked = true
+	case <-time.After(100 * time.Millisecond):
+	}
+	require.False(t, panicked)
+}