PaperMC/patches/server-remapped/0510-Fix-Per-World-Difficulty-Remembering-Difficulty.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 28 Jun 2020 03:59:10 -0400
Subject: [PATCH] Fix Per World Difficulty / Remembering Difficulty

Fixes per world difficulty with /difficulty command and also
makes it so that the server keeps the last difficulty used instead
of restoring the server.properties every single load.

diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index f530c739b6aee3718eb5d0e0e6a09d882d817c68..19544b794b5a46c129016172798ff7294fcfed33 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -1645,11 +1645,15 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         }
     }
 
-    public void setDifficulty(Difficulty enumdifficulty, boolean forceUpdate) {
-        if (forceUpdate || !this.worldData.isDifficultyLocked()) {
-            this.worldData.setDifficulty(this.worldData.isHardcore() ? Difficulty.HARD : enumdifficulty);
-            this.updateMobSpawningFlags();
-            this.getPlayerList().getPlayers().forEach(this::sendDifficultyUpdate);
+    // Paper start - fix per world difficulty
+    public void setWorldDifficulty(ServerLevel world, Difficulty enumdifficulty, boolean forcefullySet) { this.a(world, enumdifficulty, forcefullySet); }
+    public void a(ServerLevel world, Difficulty enumdifficulty, boolean flag) {
+        PrimaryLevelData worldData = world.worldDataServer;
+        if (flag || !worldData.isDifficultyLocked()) {
+            worldData.setDifficulty(worldData.isHardcore() ? Difficulty.HARD : enumdifficulty);
+            world.setSpawnSettings(worldData.getDifficulty() != Difficulty.PEACEFUL && ((DedicatedServer) this).settings.getProperties().spawnMonsters, this.isSpawningAnimals());
+            //this.getPlayerList().getPlayers().forEach(this::b); // Commented: WorldDataServer#setDifficulty handles updating players' difficulties
+            // Paper end
         }
     }
 
diff --git a/src/main/java/net/minecraft/server/commands/DifficultyCommand.java b/src/main/java/net/minecraft/server/commands/DifficultyCommand.java
index 106c633a91fea6c27d76d43d4678c00287b0992a..f0dfa78b13a774f5c6139efc70750a154961cede 100644
--- a/src/main/java/net/minecraft/server/commands/DifficultyCommand.java
+++ b/src/main/java/net/minecraft/server/commands/DifficultyCommand.java
@@ -7,6 +7,7 @@ import com.mojang.brigadier.exceptions.DynamicCommandExceptionType;
 import net.minecraft.commands.CommandSourceStack;
 import net.minecraft.network.chat.TranslatableComponent;
 import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
 import net.minecraft.world.Difficulty;
 
 public class DifficultyCommand {
@@ -41,10 +42,11 @@ public class DifficultyCommand {
     public static int setDifficulty(CommandSourceStack source, Difficulty difficulty) throws CommandSyntaxException {
         MinecraftServer minecraftserver = source.getServer();
 
-        if (minecraftserver.getWorldData().getDifficulty() == difficulty) {
+        ServerLevel world = source.getLevel(); // Paper
+        if (world.worldDataServer.getDifficulty() == difficulty) { // Paper
             throw DifficultyCommand.ERROR_ALREADY_DIFFICULT.create(difficulty.getKey());
         } else {
-            minecraftserver.setDifficulty(difficulty, true);
+            minecraftserver.a(world, difficulty, true); // Paper
             source.sendSuccess(new TranslatableComponent("commands.difficulty.success", new Object[]{difficulty.getDisplayName()}), true);
             return 0;
         }
diff --git a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
index 6477ba1f31d977f8199fb4c7532938920b385ae7..95f9863bbccaa23d08c409792314df4f2397a317 100644
--- a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
+++ b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
@@ -359,7 +359,7 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
 
     @Override
     public void forceDifficulty() {
-        this.setDifficulty(this.getProperties().difficulty, true);
+        //this.a(this.getDedicatedServerProperties().difficulty, true); // Paper - Don't overwrite level.dat's difficulty, keep current
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index 471370a9aafa3eda83beb4097c6233650bd155ee..773f2589c14e16d2f5b01a6dbd48e09d17d19c7e 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -3039,7 +3039,7 @@ public class ServerGamePacketListenerImpl implements ServerGamePacketListener {
     public void handleChangeDifficulty(ServerboundChangeDifficultyPacket packet) {
         PacketUtils.ensureRunningOnSameThread(packet, this, this.player.getLevel());
         if (this.player.hasPermissions(2) || this.isSingleplayerOwner()) {
-            this.server.setDifficulty(packet.getDifficulty(), false);
+            //this.minecraftServer.a(packetplayindifficultychange.b(), false); // Paper - don't allow clients to change this
         }
     }