Remove wall-time / unused skip tick protection (#11412)

Spigot still maintains some partial implementation of "tick skipping", a
practice in which the MinecraftServer.currentTick field is updated not
by an increment of one per actual tick, but instead set to
System.currentTimeMillis() / 50. This behaviour means that the tracked
tick may "skip" a tick value in case a previous tick took more than the
expected 50ms.

To compensate for this in important paths, spigot/craftbukkit
implements "wall-time". Instead of incrementing/decrementing ticks on
block entities/entities by one for each call to their tick() method,
they instead increment/decrement important values, like
an ItemEntity's age or pickupDelay, by the difference of
`currentTick - lastTick`, where `lastTick` is the value of
`currentTick` during the last tick() call.

These "fixes" however do not play nicely with minecraft's simulation
distance as entities/block entities implementing the above behaviour
would "catch up" their values when moving from a non-ticking chunk to a
ticking one as their `lastTick` value remains stuck on the last tick in
a ticking chunk and hence lead to a large "catch up" once ticked again.

Paper completely removes the "tick skipping" behaviour (See patch
"Further-improve-server-tick-loop"), making the above precautions
completely unnecessary, which also rids paper of the previous described
incompatibility with non-ticking chunks.

1 files changed, 38 insertions, 0 deletions

diff --git a/patches/server/0947-Item-Mutation-Fixes.patch b/patches/server/0947-Item-Mutation-Fixes.patch
new file mode 100644
index 0000000000..bad3be61f9
--- /dev/null
+++ b/patches/server/0947-Item-Mutation-Fixes.patch
@@ -0,0 +1,38 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Owen1212055 <[email protected]>
+Date: Wed, 20 Mar 2024 20:41:35 -0400
+Subject: [PATCH] Item Mutation Fixes
+
+
+diff --git a/src/main/java/net/minecraft/world/inventory/EnchantmentMenu.java b/src/main/java/net/minecraft/world/inventory/EnchantmentMenu.java
+index fff1c39920e7d7051dfe3dd39c77865d3bdf113e..1ef014b29645ed09ccffb898f1819428c3dc6259 100644
+--- a/src/main/java/net/minecraft/world/inventory/EnchantmentMenu.java
++++ b/src/main/java/net/minecraft/world/inventory/EnchantmentMenu.java
+@@ -232,7 +232,7 @@ public class EnchantmentMenu extends AbstractContainerMenu {
+                 return false;
+             } else if (this.costs[id] > 0 && !itemstack.isEmpty() && (player.experienceLevel >= j && player.experienceLevel >= this.costs[id] || player.getAbilities().instabuild)) {
+                 this.access.execute((world, blockposition) -> {
+-                    ItemStack itemstack2 = itemstack;
++                    ItemStack itemstack2 = itemstack; // Paper - diff on change
+                     List<EnchantmentInstance> list = this.getEnchantmentList(world.registryAccess(), itemstack, id, this.costs[id]);
+ 
+                     // CraftBukkit start
+@@ -255,10 +255,16 @@ public class EnchantmentMenu extends AbstractContainerMenu {
+                             return;
+                         }
+                         // CraftBukkit end
+-                        if (itemstack.is(Items.BOOK)) {
+-                            itemstack2 = itemstack.transmuteCopy(Items.ENCHANTED_BOOK);
++                        // Paper start
++                        itemstack2 = org.bukkit.craftbukkit.inventory.CraftItemStack.getOrCloneOnMutation(item, event.getItem());
++                        if (itemstack2 != itemstack) {
+                             this.enchantSlots.setItem(0, itemstack2);
+                         }
++                        if (itemstack2.is(Items.BOOK)) {
++                            itemstack2 = itemstack2.transmuteCopy(Items.ENCHANTED_BOOK);
++                            this.enchantSlots.setItem(0, itemstack2);
++                        }
++                        // Paper end
+ 
+                         // CraftBukkit start
+                         for (Map.Entry<org.bukkit.enchantments.Enchantment, Integer> entry : event.getEnchantsToAdd().entrySet()) {