Paper/Spigot-Server-Patches/0536-Thread-Safe-Vanilla-Command-permission-checking.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 11 Jul 2020 03:54:28 -0400
Subject: [PATCH] Thread Safe Vanilla Command permission checking

Datapacks check this on load and are built concurrently. This was breaking them badly due
to race conditions.

Plus, .canUse we want to be safe for async anyways.

diff --git a/src/main/java/com/mojang/brigadier/tree/CommandNode.java b/src/main/java/com/mojang/brigadier/tree/CommandNode.java
index 6976da79b20280fcd72dcfb8b48e2eb73257faf2..d9c47f3fc18266df3be1f564c01dfc3e26941380 100644
--- a/src/main/java/com/mojang/brigadier/tree/CommandNode.java
+++ b/src/main/java/com/mojang/brigadier/tree/CommandNode.java
@@ -75,10 +75,10 @@ public abstract class CommandNode<S> implements Comparable<CommandNode<S>> {
     public synchronized boolean canUse(final S source) {
         if (source instanceof CommandListenerWrapper) {
             try {
-                ((CommandListenerWrapper) source).currentCommand = this;
+                ((CommandListenerWrapper) source).currentCommand.set(this); // Paper
                 return requirement.test(source);
             } finally {
-                ((CommandListenerWrapper) source).currentCommand = null;
+                ((CommandListenerWrapper) source).currentCommand.set(null); // Paper
             }
         }
         // CraftBukkit end
diff --git a/src/main/java/net/minecraft/server/CommandListenerWrapper.java b/src/main/java/net/minecraft/server/CommandListenerWrapper.java
index 7608b5021d66c39b8121f33829cd09d77c847277..90b0cf6470711101400d723747d1f302cf6e23bd 100644
--- a/src/main/java/net/minecraft/server/CommandListenerWrapper.java
+++ b/src/main/java/net/minecraft/server/CommandListenerWrapper.java
@@ -33,7 +33,7 @@ public class CommandListenerWrapper implements ICompletionProvider, com.destroys
     private final ResultConsumer<CommandListenerWrapper> l;
     private final ArgumentAnchor.Anchor m;
     private final Vec2F n;
-    public volatile CommandNode currentCommand; // CraftBukkit
+    public ThreadLocal<CommandNode> currentCommand = new ThreadLocal<>(); // CraftBukkit // Paper
 
     public CommandListenerWrapper(ICommandListener icommandlistener, Vec3D vec3d, Vec2F vec2f, WorldServer worldserver, int i, String s, IChatBaseComponent ichatbasecomponent, MinecraftServer minecraftserver, @Nullable Entity entity) {
         this(icommandlistener, vec3d, vec2f, worldserver, i, s, ichatbasecomponent, minecraftserver, entity, false, (commandcontext, flag, j) -> {
@@ -150,9 +150,11 @@ public class CommandListenerWrapper implements ICompletionProvider, com.destroys
     @Override
     public boolean hasPermission(int i) {
         // CraftBukkit start
-        CommandNode currentCommand = this.currentCommand;
+        // Paper start - fix concurrency issue
+        CommandNode currentCommand = this.currentCommand.get();
         if (currentCommand != null) {
             return hasPermission(i, org.bukkit.craftbukkit.command.VanillaCommandWrapper.getPermission(currentCommand));
+            // Paper end
         }
         // CraftBukkit end