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
@@ -20,11 +_,37 @@
     protected int age;
     protected int forcedAge;
     protected int forcedAgeTimer;
+    public boolean ageLocked; // CraftBukkit
 
     protected AgeableMob(EntityType<? extends AgeableMob> entityType, Level level) {
         super(entityType, level);
     }
 
+    // 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 level, DifficultyInstance difficulty, EntitySpawnReason spawnReason, @Nullable SpawnGroupData spawnGroupData
@@ -66,6 +_,7 @@
     }
 
     public void ageUp(int amount, boolean forced) {
+        if (this.ageLocked) return; // Paper - Honor ageLock
         int age = this.getAge();
         age += amount * 20;
         if (age > 0) {
@@ -104,6 +_,7 @@
         super.addAdditionalSaveData(compound);
         compound.putInt("Age", this.getAge());
         compound.putInt("ForcedAge", this.forcedAge);
+        compound.putBoolean("AgeLocked", this.ageLocked); // CraftBukkit
     }
 
     @Override
@@ -111,6 +_,7 @@
         super.readAdditionalSaveData(compound);
         this.setAge(compound.getInt("Age"));
         this.forcedAge = compound.getInt("ForcedAge");
+        this.ageLocked = compound.getBoolean("AgeLocked"); // CraftBukkit
     }
 
     @Override
@@ -125,7 +_,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(1.0), this.getRandomY() + 0.5, this.getRandomZ(1.0), 0.0, 0.0, 0.0);