fix: remove old HTTPRoute's parents' statuses

internal/controllers/gateway/httproute_controller.go

@@ -529,9 +529,33 @@ var httprouteParentKind = "Gateway"
 // considered "attached" to a given HTTPRoute and ensures that the status
 // for the HTTPRoute is updated appropriately.
 func (r *HTTPRouteReconciler) ensureGatewayReferenceStatusAdded(ctx context.Context, httproute *gatewayapi.HTTPRoute, gateways ...supportedGatewayWithCondition) (bool, error) {
-	// map the existing parentStatues to avoid duplications
+	// Map the existing parentStatues to avoid duplications.
 	parentStatuses := getParentStatuses(httproute, httproute.Status.Parents)
 
+	parentRefKey := func(parentRef gatewayapi.ParentReference) string {
+		namespace := httproute.Namespace
+		if parentRef.Namespace != nil {
+			namespace = string(*parentRef.Namespace)
+		}
+		sectionName := ""
+		if parentRef.SectionName != nil {
+			sectionName = string(*parentRef.SectionName)
+		}
+		return fmt.Sprintf("%s/%s/%s", namespace, parentRef.Name, sectionName)
+	}
+
+	// Discard parent statuses that are not found in the current parentRefs.
+	currentParentRefs := httproute.Spec.ParentRefs
+	currentParentRefsMap := lo.SliceToMap(currentParentRefs, func(ref gatewayapi.ParentReference) (string, struct{}) {
+		return parentRefKey(ref), struct{}{}
+	})
+	for _, parentStatus := range parentStatuses {
+		key := parentRefKey(parentStatus.ParentRef)
+		if _, ok := currentParentRefsMap[key]; !ok {
+			delete(parentStatuses, key)
+		}
+	}
+
 	// overlay the parent ref statuses for all new gateway references
 	statusChangesWereMade := false
 	for _, gateway := range gateways {