Paper/paper-server/patches/sources/net/minecraft/commands/arguments/MessageArgument.java.patch

--- a/net/minecraft/commands/arguments/MessageArgument.java
+++ b/net/minecraft/commands/arguments/MessageArgument.java
@@ -40,6 +_,11 @@
 
     public static void resolveChatMessage(CommandContext<CommandSourceStack> context, String key, Consumer<PlayerChatMessage> callback) throws CommandSyntaxException {
         MessageArgument.Message message = context.getArgument(key, MessageArgument.Message.class);
+        // Paper start
+        resolveChatMessage(message, context, key, callback);
+    }
+    public static void resolveChatMessage(MessageArgument.Message message, CommandContext<CommandSourceStack> context, String key, Consumer<PlayerChatMessage> callback) throws CommandSyntaxException {
+        // Paper end
         CommandSourceStack commandSourceStack = context.getSource();
         Component component = message.resolveComponent(commandSourceStack);
         CommandSigningContext signingContext = commandSourceStack.getSigningContext();
@@ -54,17 +_,21 @@
     private static void resolveSignedMessage(Consumer<PlayerChatMessage> callback, CommandSourceStack source, PlayerChatMessage message) {
         MinecraftServer server = source.getServer();
         CompletableFuture<FilteredText> completableFuture = filterPlainText(source, message);
-        Component component = server.getChatDecorator().decorate(source.getPlayer(), message.decoratedContent());
-        source.getChatMessageChainer().append(completableFuture, filteredText -> {
-            PlayerChatMessage playerChatMessage = message.withUnsignedContent(component).filter(filteredText.mask());
+        // Paper start - support asynchronous chat decoration
+        CompletableFuture<Component> componentFuture = server.getChatDecorator().decorate(source.getPlayer(), source, message.decoratedContent());
+        source.getChatMessageChainer().append(CompletableFuture.allOf(completableFuture, componentFuture), filtered -> {
+            PlayerChatMessage playerChatMessage = message.withUnsignedContent(componentFuture.join()).filter(completableFuture.join().mask());
+            // Paper end - support asynchronous chat decoration
             callback.accept(playerChatMessage);
         });
     }
 
     private static void resolveDisguisedMessage(Consumer<PlayerChatMessage> callback, CommandSourceStack source, PlayerChatMessage message) {
         ChatDecorator chatDecorator = source.getServer().getChatDecorator();
-        Component component = chatDecorator.decorate(source.getPlayer(), message.decoratedContent());
-        callback.accept(message.withUnsignedContent(component));
+        // Paper start - support asynchronous chat decoration
+        CompletableFuture<Component> componentFuture = chatDecorator.decorate(source.getPlayer(), source, message.decoratedContent());
+        source.getChatMessageChainer().append(componentFuture, (result) -> callback.accept(message.withUnsignedContent(result)));
+        // Paper end - support asynchronous chat decoration
     }
 
     private static CompletableFuture<FilteredText> filterPlainText(CommandSourceStack source, PlayerChatMessage message) {