tests that caught the previous two bugs.

listener.go

@@ -67,12 +67,13 @@ func (rl *Relay) removeListenerId(ws *WebSocket, id string) {
 
 	if specs, ok := rl.clients[ws]; ok {
 		// swap delete specs that match this id
-		nswaps := 0
-		for s, spec := range specs {
+		for s := len(specs) - 1; s >= 0; s-- {
+			spec := specs[s]
 			if spec.id == id {
 				spec.cancel(ErrSubscriptionClosedByClient)
-				specs[s] = specs[len(specs)-1-nswaps]
-				nswaps++
+				specs[s] = specs[len(specs)-1]
+				specs = specs[0 : len(specs)-1]
+				rl.clients[ws] = specs
 
 				// swap delete listeners one at a time, as they may be each in a different subrelay
 				srl := spec.subrelay // == rl in normal cases, but different when this came from a route
@@ -82,7 +83,8 @@ func (rl *Relay) removeListenerId(ws *WebSocket, id string) {
 					moved := srl.listeners[movedFromIndex] // this wasn't removed, but will be moved
 					srl.listeners[spec.index] = moved
 
-					// update the index of the listener we just moved
+					// now we must update the the listener we just moved
+					// so its .index reflects its new position on srl.listeners
 					movedSpecs := rl.clients[moved.ws]
 					idx := slices.IndexFunc(movedSpecs, func(ls listenerSpec) bool {
 						return ls.index == movedFromIndex
@@ -93,7 +95,6 @@ func (rl *Relay) removeListenerId(ws *WebSocket, id string) {
 				srl.listeners = srl.listeners[0 : len(srl.listeners)-1] // finally reduce the slice length
 			}
 		}
-		rl.clients[ws] = specs[0 : len(specs)-nswaps]
 	}
 }
 
@@ -102,7 +103,7 @@ func (rl *Relay) removeClientAndListeners(ws *WebSocket) {
 	defer rl.clientsMutex.Unlock()
 	if specs, ok := rl.clients[ws]; ok {
 		// swap delete listeners and delete client (all specs will be deleted)
-		for _, spec := range specs {
+		for s, spec := range specs {
 			// no need to cancel contexts since they inherit from the main connection context
 			// just delete the listeners (swap-delete)
 			srl := spec.subrelay
@@ -112,7 +113,12 @@ func (rl *Relay) removeClientAndListeners(ws *WebSocket) {
 				moved := srl.listeners[movedFromIndex] // this wasn't removed, but will be moved
 				srl.listeners[spec.index] = moved
 
-				// update the index of the listener we just moved
+				// temporarily update the spec of the listener being removed to have index == -1
+				// (since it was removed) so it doesn't match in the search below
+				rl.clients[ws][s].index = -1
+
+				// now we must update the the listener we just moved
+				// so its .index reflects its new position on srl.listeners
 				movedSpecs := rl.clients[moved.ws]
 				idx := slices.IndexFunc(movedSpecs, func(ls listenerSpec) bool {
 					return ls.index == movedFromIndex

listener_test.go

@@ -1,6 +1,7 @@
 package khatru
 
 import (
+	"math/rand"
 	"testing"
 
 	"github.com/nbd-wtf/go-nostr"
@@ -404,3 +405,99 @@ func TestListenerMoreStuffWithMultipleRelays(t *testing.T) {
 		}, rlz.listeners)
 	})
 }
+
+func TestRandomListenerClientRemoving(t *testing.T) {
+	rl := NewRelay()
+
+	f := nostr.Filter{Kinds: []int{1}}
+	cancel := func(cause error) {}
+
+	websockets := make([]*WebSocket, 0, 20)
+
+	l := 0
+
+	for i := 0; i < 20; i++ {
+		ws := &WebSocket{}
+		websockets = append(websockets, ws)
+		rl.clients[ws] = nil
+	}
+
+	for j := 0; j < 20; j++ {
+		for i := 0; i < 20; i++ {
+			ws := websockets[i]
+			w := string(rune(i + 65))
+
+			if rand.Intn(2) < 1 {
+				l++
+				rl.addListener(ws, w+":"+string(rune(j+97)), rl, f, cancel)
+			}
+		}
+	}
+
+	require.Len(t, rl.clients, 20)
+	require.Len(t, rl.listeners, l)
+
+	for ws := range rl.clients {
+		rl.removeClientAndListeners(ws)
+	}
+
+	require.Len(t, rl.clients, 0)
+	require.Len(t, rl.listeners, 0)
+}
+
+func TestRandomListenerIdRemoving(t *testing.T) {
+	rl := NewRelay()
+
+	f := nostr.Filter{Kinds: []int{1}}
+	cancel := func(cause error) {}
+
+	websockets := make([]*WebSocket, 0, 20)
+
+	type wsid struct {
+		ws *WebSocket
+		id string
+	}
+
+	subs := make([]wsid, 0, 20*20)
+	extra := 0
+
+	for i := 0; i < 20; i++ {
+		ws := &WebSocket{}
+		websockets = append(websockets, ws)
+		rl.clients[ws] = nil
+	}
+
+	for j := 0; j < 20; j++ {
+		for i := 0; i < 20; i++ {
+			ws := websockets[i]
+			w := string(rune(i + 65))
+
+			if rand.Intn(2) < 1 {
+				id := w + ":" + string(rune(j+97))
+				rl.addListener(ws, id, rl, f, cancel)
+				subs = append(subs, wsid{ws, id})
+
+				if rand.Intn(5) < 1 {
+					rl.addListener(ws, id, rl, f, cancel)
+					extra++
+				}
+			}
+		}
+	}
+
+	require.Len(t, rl.clients, 20)
+	require.Len(t, rl.listeners, len(subs)+extra)
+
+	rand.Shuffle(len(subs), func(i, j int) {
+		subs[i], subs[j] = subs[j], subs[i]
+	})
+	for _, wsidToRemove := range subs {
+		rl.removeListenerId(wsidToRemove.ws, wsidToRemove.id)
+	}
+
+	require.Len(t, rl.listeners, 0)
+	require.Len(t, rl.clients, 20)
+	for _, specs := range rl.clients {
+		require.Len(t, specs, 0)
+	}
+}