PaperMC/paper-server/patches/sources/net/minecraft/world/entity/AgeableMob.java.patch

--- a/net/minecraft/world/entity/AgeableMob.java
+++ b/net/minecraft/world/entity/AgeableMob.java
@@ -21,12 +21,38 @@
     protected int age;
     protected int forcedAge;
     protected int forcedAgeTimer;
+    public boolean ageLocked; // CraftBukkit
 
     protected AgeableMob(EntityType<? extends AgeableMob> type, Level world) {
         super(type, world);
     }
 
+    // Spigot start
     @Override
+    public void inactiveTick()
+    {
+        super.inactiveTick();
+        if ( this.level().isClientSide || this.ageLocked )
+        { // CraftBukkit
+            this.refreshDimensions();
+        } else
+        {
+            int i = this.getAge();
+
+            if ( i < 0 )
+            {
+                ++i;
+                this.setAge( i );
+            } else if ( i > 0 )
+            {
+                --i;
+                this.setAge( i );
+            }
+        }
+    }
+    // Spigot end
+
+    @Override
     public SpawnGroupData finalizeSpawn(ServerLevelAccessor world, DifficultyInstance difficulty, EntitySpawnReason spawnReason, @Nullable SpawnGroupData entityData) {
         if (entityData == null) {
             entityData = new AgeableMob.AgeableMobGroupData(true);
@@ -60,6 +86,7 @@
     }
 
     public void ageUp(int age, boolean overGrow) {
+        if (this.ageLocked) return; // Paper - Honor ageLock
         int j = this.getAge();
         int k = j;
 
@@ -104,6 +131,7 @@
         super.addAdditionalSaveData(nbt);
         nbt.putInt("Age", this.getAge());
         nbt.putInt("ForcedAge", this.forcedAge);
+        nbt.putBoolean("AgeLocked", this.ageLocked); // CraftBukkit
     }
 
     @Override
@@ -111,6 +139,7 @@
         super.readAdditionalSaveData(nbt);
         this.setAge(nbt.getInt("Age"));
         this.forcedAge = nbt.getInt("ForcedAge");
+        this.ageLocked = nbt.getBoolean("AgeLocked"); // CraftBukkit
     }
 
     @Override
@@ -125,7 +154,7 @@
     @Override
     public void aiStep() {
         super.aiStep();
-        if (this.level().isClientSide) {
+        if (this.level().isClientSide || this.ageLocked) { // CraftBukkit
             if (this.forcedAgeTimer > 0) {
                 if (this.forcedAgeTimer % 4 == 0) {
                     this.level().addParticle(ParticleTypes.HAPPY_VILLAGER, this.getRandomX(1.0D), this.getRandomY() + 0.5D, this.getRandomZ(1.0D), 0.0D, 0.0D, 0.0D);