PaperMC/nms-patches/EntitySmallFireball.patch

--- a/net/minecraft/server/EntitySmallFireball.java
+++ b/net/minecraft/server/EntitySmallFireball.java
@@ -1,5 +1,7 @@
 package net.minecraft.server;
 
+import org.bukkit.event.entity.EntityCombustByEntityEvent; // CraftBukkit
+
 public class EntitySmallFireball extends EntityFireballFireball {
 
     public EntitySmallFireball(EntityTypes<? extends EntitySmallFireball> entitytypes, World world) {
@@ -8,6 +10,11 @@
 
     public EntitySmallFireball(World world, EntityLiving entityliving, double d0, double d1, double d2) {
         super(EntityTypes.SMALL_FIREBALL, entityliving, d0, d1, d2, world);
+        // CraftBukkit start
+        if (this.shooter != null && this.shooter instanceof EntityInsentient) {
+            isIncendiary = this.world.getGameRules().getBoolean(GameRules.MOB_GRIEFING);
+        }
+        // CraftBukkit end
     }
 
     public EntitySmallFireball(World world, double d0, double d1, double d2, double d3, double d4, double d5) {
@@ -24,7 +31,16 @@
                 if (!entity.isFireProof()) {
                     int i = entity.ad();
 
-                    entity.setOnFire(5);
+                    // CraftBukkit start - Entity damage by entity event + combust event
+                    if (isIncendiary) {
+                        EntityCombustByEntityEvent event = new EntityCombustByEntityEvent((org.bukkit.entity.Projectile) this.getBukkitEntity(), entity.getBukkitEntity(), 5);
+                        entity.world.getServer().getPluginManager().callEvent(event);
+
+                        if (!event.isCancelled()) {
+                            entity.setOnFire(event.getDuration(), false);
+                        }
+                    }
+                    // CraftBukkit end
                     boolean flag = entity.damageEntity(DamageSource.fireball(this, this.shooter), 5.0F);
 
                     if (flag) {
@@ -33,11 +49,11 @@
                         entity.g(i);
                     }
                 }
-            } else if (this.shooter == null || !(this.shooter instanceof EntityInsentient) || this.world.getGameRules().getBoolean(GameRules.MOB_GRIEFING)) {
+            } else if (isIncendiary) { // CraftBukkit
                 MovingObjectPositionBlock movingobjectpositionblock = (MovingObjectPositionBlock) movingobjectposition;
                 BlockPosition blockposition = movingobjectpositionblock.getBlockPosition().shift(movingobjectpositionblock.getDirection());
 
-                if (this.world.isEmpty(blockposition)) {
+                if (this.world.isEmpty(blockposition) && !org.bukkit.craftbukkit.event.CraftEventFactory.callBlockIgniteEvent(world, blockposition, this).isCancelled()) { // CraftBukkit
                     this.world.setTypeUpdate(blockposition, Blocks.FIRE.getBlockData());
                 }
             }