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 5e3fc338b0fe69a74465567e69721bc28c64dd17..ca0d664487a65a4768f0e65af6a320fd1875de8f 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>> {
         // CraftBukkit start
         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 fa0f247e51c20ea0e3cbaccbc8dbb2a153d6121f..a4995ddc82100bc460cd2021dcfa8389769d5da0 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 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) -> {
@@ -143,8 +143,11 @@ public class CommandListenerWrapper implements ICompletionProvider, com.destroys
     @Override
     public boolean hasPermission(int i) {
         // CraftBukkit start
+        // 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