`/unpublish` succeeds when the game is not published despite the failure message

When using /unpublish in a singleplayer world that is not published, even though the command correctly shows a failure message, it actually technically succeeds, which can break data packs expecting the command’s success value to be 0.

How to reproduce:

1. Open a singleplayer world and don’t enable multiplayer.

2. Execute the following command:

   /execute store success storage mc-308405:test success_value int 1 run unpublish

3. Execute the following command:

   /data get storage mc-308405:test success_value

   → ❌ The value stored is 1, indicating the command executed by the run argument of the first command succeeded.

Expected result:

The /unpublish command would fail when the game is not published.

Observed result:

The /unpublish command succeeds when the game is not published despite a failure message being sent.

Code analysis:

This code analysis uses 26.2 Snapshot 8’s code, decompiled using Vineflower.

In the net.minecraft.server.commands.UnpublishCommand class, there is a method called unpublish, which is called when the command is run. This method is shown below:

private static int unpublish(final CommandSourceStack source) {
   if (source.getServer().unpublishServer()) {
      source.sendSuccess(() -> Component.translatable("commands.unpublish.success"), true);
      return 1;
   } else {
      source.sendFailure(Component.translatable("commands.unpublish.notPublished"));
      return 0;
   }
}

The method tries to unpublish the integrated server, and if it fails (if the game wasn’t published), it sends a failure message and returns a Brigadier return value. When a command returns a value, it is considered successful, and its success value is therefore set to 1. Most other commands, when failing, throw a CommandSyntaxException instead of returning a value, since the game only sets a command’s success value to 0 when such an exception is thrown.