From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Nassim Jahnke <nassim@njahnke.dev>
Date: Tue, 2 Aug 2022 19:16:23 +0200
Subject: [PATCH] Fix command preprocess cancelling and command changing


diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index f082e121331be8aee523751a2d3f3393e3b0d02c..ca7afdbfa936801e53e8bb0d154538bc0f042ad3 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -2259,13 +2259,24 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         PlayerCommandPreprocessEvent event = new PlayerCommandPreprocessEvent(this.getCraftPlayer(), command, new LazyPlayerSet(this.server));
         this.cserver.getPluginManager().callEvent(event);
 
-        if (event.isCancelled()) {
-            return;
-        }
         command = event.getMessage().substring(1);
 
-        ParseResults<CommandSourceStack> parseresults = this.parseCommand(command);
-        Map<String, PlayerChatMessage> map = (packet.command().equals(command)) ? this.collectSignedArguments(packet, PreviewableCommand.of(parseresults)) : Collections.emptyMap();
+        // Paper start - send message headers for cancelled or changed commands
+        ParseResults<CommandSourceStack> parseresults = this.parseCommand(packet.command());
+        Map<String, PlayerChatMessage> map = this.collectSignedArguments(packet, PreviewableCommand.of(parseresults));
+        if (event.isCancelled() || !packet.command().equals(command)) {
+            for (final PlayerChatMessage message : map.values()) {
+                player.server.getPlayerList().broadcastMessageHeader(message, Set.of());
+            }
+            if (event.isCancelled()) {
+                return;
+            }
+
+            // Remove signatures if the command was changed and use the changed command source stack
+            map.clear();
+            parseresults = this.parseCommand(command);
+        }
+        // Paper end
         // CraftBukkit end
         Iterator iterator = map.values().iterator();
 
@@ -2569,6 +2580,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
                 }
             });
         } else if (this.player.getChatVisibility() == ChatVisiblity.SYSTEM) { // Re-add "Command Only" flag check
+            this.server.getPlayerList().broadcastMessageHeader(message, Set.of()); // Paper
             this.send(new ClientboundSystemChatPacket(Component.translatable("chat.cannotSend").withStyle(ChatFormatting.RED), false));
         } else {
             this.chat(s, message, true);