PaperMC/paper-server/nms-patches/net/minecraft/world/level/MobSpawnerAbstract.patch

--- a/net/minecraft/world/level/MobSpawnerAbstract.java
+++ b/net/minecraft/world/level/MobSpawnerAbstract.java
@@ -52,6 +52,7 @@
 
     public void setEntityId(EntityTypes<?> entitytypes, @Nullable World world, RandomSource randomsource, BlockPosition blockposition) {
         this.getOrCreateNextSpawnData(world, randomsource, blockposition).getEntityToSpawn().putString("id", BuiltInRegistries.ENTITY_TYPE.getKey(entitytypes).toString());
+        this.spawnPotentials = SimpleWeightedRandomList.empty(); // CraftBukkit - SPIGOT-3496, MC-92282
     }
 
     private boolean isNearPlayer(World world, BlockPosition blockposition) {
@@ -154,7 +155,12 @@
                             }
                         }
 
-                        if (!worldserver.tryAddFreshEntityWithPassengers(entity)) {
+                        // CraftBukkit start
+                        if (org.bukkit.craftbukkit.event.CraftEventFactory.callSpawnerSpawnEvent(entity, blockposition).isCancelled()) {
+                            continue;
+                        }
+                        if (!worldserver.tryAddFreshEntityWithPassengers(entity, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SPAWNER)) {
+                            // CraftBukkit end
                             this.delay(worldserver, blockposition);
                             return;
                         }