craftbukkit/nms-patches/net/minecraft/world/entity/projectile/ThrownSplashPotion.patch

--- a/net/minecraft/world/entity/projectile/ThrownSplashPotion.java
+++ b/net/minecraft/world/entity/projectile/ThrownSplashPotion.java
@@ -17,6 +17,16 @@
 import net.minecraft.world.level.World;
 import net.minecraft.world.phys.AxisAlignedBB;
 
+// CraftBukkit start
+import java.util.HashMap;
+import java.util.Map;
+import net.minecraft.server.level.EntityPlayer;
+import net.minecraft.world.effect.MobEffects;
+import net.minecraft.world.phys.MovingObjectPosition;
+import org.bukkit.craftbukkit.entity.CraftLivingEntity;
+import org.bukkit.entity.LivingEntity;
+// CraftBukkit end
+
 public class ThrownSplashPotion extends EntityPotion {
 
     public ThrownSplashPotion(EntityTypes<? extends ThrownSplashPotion> entitytypes, World world) {
@@ -37,12 +47,13 @@
     }
 
     @Override
-    public void onHitAsPotion(WorldServer worldserver, ItemStack itemstack, @Nullable Entity entity) {
+    public void onHitAsPotion(WorldServer worldserver, ItemStack itemstack, @Nullable Entity entity, MovingObjectPosition position) { // CraftBukkit - Pass MovingObjectPosition
         PotionContents potioncontents = (PotionContents) itemstack.getOrDefault(DataComponents.POTION_CONTENTS, PotionContents.EMPTY);
         float f = (Float) itemstack.getOrDefault(DataComponents.POTION_DURATION_SCALE, 1.0F);
         Iterable<MobEffect> iterable = potioncontents.getAllEffects();
         AxisAlignedBB axisalignedbb = this.getBoundingBox().inflate(4.0D, 2.0D, 4.0D);
         List<EntityLiving> list = this.level().<EntityLiving>getEntitiesOfClass(EntityLiving.class, axisalignedbb);
+        Map<LivingEntity, Double> affected = new HashMap<LivingEntity, Double>(); // CraftBukkit
 
         if (!list.isEmpty()) {
             Entity entity1 = this.getEffectSource();
@@ -60,8 +71,38 @@
                             d1 = 1.0D - Math.sqrt(d0) / 4.0D;
                         }
 
+                        // CraftBukkit start
+                        affected.put((LivingEntity) entityliving.getBukkitEntity(), d1);
+                    }
+                }
+            }
+        }
+
+        {
+            {
+                org.bukkit.event.entity.PotionSplashEvent event = org.bukkit.craftbukkit.event.CraftEventFactory.callPotionSplashEvent(this, position, affected);
+                if (!event.isCancelled() && list != null && !list.isEmpty()) { // do not process effects if there are no effects to process
+                    Entity entity1 = this.getEffectSource();
+                    for (LivingEntity victim : event.getAffectedEntities()) {
+                        if (!(victim instanceof CraftLivingEntity)) {
+                            continue;
+                        }
+
+                        EntityLiving entityliving = ((CraftLivingEntity) victim).getHandle();
+                        double d1 = event.getIntensity(victim);
+                        // CraftBukkit end
+
                         for (MobEffect mobeffect : iterable) {
                             Holder<MobEffectList> holder = mobeffect.getEffect();
+                            // CraftBukkit start - Abide by PVP settings - for players only!
+                            if (!this.level().pvpMode && this.getOwner() instanceof EntityPlayer && entityliving instanceof EntityPlayer && entityliving != this.getOwner()) {
+                                MobEffectList mobeffectlist = (MobEffectList) holder.value();
+                                if (mobeffectlist == MobEffects.SLOWNESS || mobeffectlist == MobEffects.MINING_FATIGUE || mobeffectlist == MobEffects.INSTANT_DAMAGE || mobeffectlist == MobEffects.BLINDNESS
+                                        || mobeffectlist == MobEffects.HUNGER || mobeffectlist == MobEffects.WEAKNESS || mobeffectlist == MobEffects.POISON) {
+                                    continue;
+                                }
+                            }
+                            // CraftBukkit end
 
                             if (((MobEffectList) holder.value()).isInstantenous()) {
                                 ((MobEffectList) holder.value()).applyInstantenousEffect(worldserver, this, this.getOwner(), entityliving, mobeffect.getAmplifier(), d1);
@@ -72,7 +113,7 @@
                                 MobEffect mobeffect1 = new MobEffect(holder, i, mobeffect.getAmplifier(), mobeffect.isAmbient(), mobeffect.isVisible());
 
                                 if (!mobeffect1.endsWithin(20)) {
-                                    entityliving.addEffect(mobeffect1, entity1);
+                                    entityliving.addEffect(mobeffect1, entity1, org.bukkit.event.entity.EntityPotionEffectEvent.Cause.POTION_SPLASH); // CraftBukkit
                                 }
                             }
                         }