/minecraft:reload fails to reload functions with custom commands on 1.16

[Combustible]

CommandAPI version
4.3 and 5.1

Minecraft version
1.16.3
This bug does not affect versions 1.15 and below.

Describe the bug
/minecraft:reload is used to reload datapacks after the server has started.

Functions can contain custom commands. When the server initially starts up, they fail to load. Then at startup CommandAPI reloads datapacks again in a special way, which causes the datapacks with custom commands to load correctly. No bugs here.

However, if you try to manually /minecraft:reload again after this, the custom commands will break again. This is because every time you trigger /minecraft:reload minecraft creates a new CommandDispatcher, with none of the custom commands in it.

Expected behavior
/minecraft:reload works with functions with custom commands

Workaround
If you happen to be using Paper and have control over your rebuilding your server's paperclip.jar, you can use this patch to work around this behavior and have /minecraft:reload work again as it did in previous versions.

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Byron Marohn <combustible@live.com>
Date: Sat, 24 Oct 2020 14:57:50 -0400
Subject: [PATCH] Monumenta - Ensure minecraft:reload uses latest
 CommandDispatcher


diff --git a/src/main/java/net/minecraft/server/DataPackResources.java b/src/main/java/net/minecraft/server/DataPackResources.java
index f6714515cc6b0265b772e5850301f6165c8f3d54..04d2916021e5d3690e60d858d481041920744f85 100644
--- a/src/main/java/net/minecraft/server/DataPackResources.java
+++ b/src/main/java/net/minecraft/server/DataPackResources.java
@@ -7,6 +7,7 @@ import java.util.concurrent.Executor;
 public class DataPackResources implements AutoCloseable {

     private static final CompletableFuture<Unit> a = CompletableFuture.completedFuture(Unit.INSTANCE);
+    public static CommandDispatcher staticDispatcher = null;
     private final IReloadableResourceManager b;
     public CommandDispatcher commandDispatcher;
     private final CraftingManager d;
@@ -23,7 +24,11 @@ public class DataPackResources implements AutoCloseable {
         this.f = new LootPredicateManager();
         this.g = new LootTableRegistry(this.f);
         this.h = new AdvancementDataWorld(this.f);
-        this.commandDispatcher = new CommandDispatcher(commanddispatcher_servertype);
+        if (staticDispatcher == null) {
+            this.commandDispatcher = new CommandDispatcher(commanddispatcher_servertype);
+        } else {
+            this.commandDispatcher = staticDispatcher;
+        }
         this.i = new CustomFunctionManager(i, this.commandDispatcher.a());
         this.b.a((IReloadListener) this.e);
         this.b.a((IReloadListener) this.f);
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
index d8d29d14559169f5e8d8b4cf63d8b427b823eb2f..f4d429781c5cf20b8127191c20377fc169c3b859 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -456,6 +456,7 @@ public final class CraftServer implements Server {
     public void syncCommands() {
         // Clear existing commands
         CommandDispatcher dispatcher = console.dataPackResources.commandDispatcher = new CommandDispatcher();
+        console.dataPackResources.staticDispatcher = dispatcher;

         // Register all commands, vanilla ones will be using the old dispatcher references
         for (Map.Entry<String, Command> entry : commandMap.getKnownCommands().entrySet()) {

You can make these edits yourself or copy this file
0626-Monumenta-Ensure-minecraft-reload-uses-latest-Comman.txt

into Spigot-Server-Patches, change it's extension from .txt to .patch and run ./paper jar

[JorelAli]

As this bug is completely out of control of the CommandAPI's capabilities, I've added a new method which will run the CommandAPI's datapack reloading sequence:

CommandAPI.reloadDatapacks();

This can be used to reload the datapacks, keeping any custom commands.

---

There is a possibility that replacing the /minecraft:reload command via Brigadier can be used to circumvent this issue, but this will require further exploration.

[JorelAli]

This can be mitigated in a paper server, due to the introduction of the ServerResourcesReloadedEvent which could be hooked into to reload the datapacks via the CommandAPI. Obviously, this isn't a solution for Spigot servers (but let's be honest, who's using Spigot in this day and age?).

I'll have to look into getting better paper support and hooking into Paper's APIs if it's present.

[JorelAli]

In 8.4.0, on Paper servers only, the CommandAPI will run its datapack reloading method when the ServerResourcesReloadedEvent is called. This is the closest thing I can think of that solves this issue - if you're on Spigot (when seriously, consider upgrading to Paper), you'll have to do it manually using CommandAPI.reloadDatapacks()