Fix crystal despawning.

src/main/java/appeng/entity/AEBaseItemEntity.java

@@ -44,8 +44,6 @@ public abstract class AEBaseItemEntity extends ItemEntity implements ICustomEnti
         this.yaw = this.random.nextFloat() * 360.0F;
         this.setVelocity(this.random.nextDouble() * 0.2D - 0.1D, 0.2D, this.random.nextDouble() * 0.2D - 0.1D);
         this.setStack(stack);
-        // FIXME FABRIC Needs replacement hook this.lifespan =
-        // stack.getEntityLifespan(world);
     }
 
     protected List<Entity> getCheckedEntitiesWithinAABBExcludingEntity(final Box region) {

src/main/java/appeng/entity/GrowingCrystalEntity.java

@@ -35,9 +35,10 @@ import appeng.client.EffectType;
 import appeng.core.AEConfig;
 import appeng.core.AppEng;
 import appeng.items.misc.CrystalSeedItem;
+import appeng.mixins.ItemEntityAccessor;
 import appeng.util.Platform;
 
-public final class GrowingCrystalEntity extends AEBaseItemEntity {
+public class GrowingCrystalEntity extends AEBaseItemEntity {
 
     public static EntityType<GrowingCrystalEntity> TYPE;
 
@@ -49,13 +50,16 @@ public final class GrowingCrystalEntity extends AEBaseItemEntity {
 
     public GrowingCrystalEntity(final World w, final double x, final double y, final double z, final ItemStack is) {
         super(TYPE, w, x, y, z, is);
-        this.setCovetedItem();
-        // FIXME FABRIC This does not actually fix despawning, we need to Mixin,
-        // probably.
     }
 
     @Override
     public void tick() {
+        // Prevent the entity from despawning
+        ItemEntityAccessor accessor = (ItemEntityAccessor) this;
+        if (!this.world.isClient && accessor.getAge() >= 1000) {
+            accessor.setAge(0);
+        }
+
         super.tick();
 
         if (!AEConfig.instance().isFeatureEnabled(AEFeature.IN_WORLD_PURIFICATION)) {

src/main/java/appeng/mixins/ItemEntityAccessor.java

@@ -0,0 +1,17 @@
+package appeng.mixins;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+import net.minecraft.entity.ItemEntity;
+
+@Mixin(ItemEntity.class)
+public interface ItemEntityAccessor {
+
+    @Accessor
+    int getAge();
+
+    @Accessor
+    void setAge(int age);
+
+}

src/main/resources/appliedenergistics2.mixins.json

@@ -24,7 +24,8 @@
     "SlotMixin",
     "TntAccessor",
     "ServerWorldCustomItemEntityMixin",
-    "BootstrapMixin"
+    "BootstrapMixin",
+    "ItemEntityAccessor"
   ],
   "client": [
     "spatial.SkyRenderMixin",