[MC-32701] Command block minecarts lose their name after re-log

The bug

Minecarts with command block don't output their default or customized name after re-log.

Reproduction steps

Rename a command block minecart item

/give @s command_block_minecart{display:{Name:"\"test\""}}

Place it on a powered activator rail
Enter a command, e.g.
```
/say message
```
✔ It prints "[test] message" in chat
Reopen the world
❌ It prints "[@] message" in chat

Code analysis

Code analysis by @unknown can be found in this comment.

Linked issues

is duplicated by 2

MC-54777 When I rename a minecart command block, place it and leave my game in single player, the minecart name becomes @ when I come back Resolved

MC-136611 Minecart with Command Block changing its name Resolved

relates to 2

MC-121903 Command block minecarts do not save execution cooldown to NBT Open

MC-266506 Command block minecarts don't show "@" default custom name when spawned via spawner until world reload Resolved

Attachments

MC-32701.mp4

Comments 25

Anon Ymus 2013-09-30T14:50:24Z

Confirmed.

Itouch2 2014-02-28T20:44:55Z

Still a concern in 1.7.4/5 and 1.8

kumasasa 2014-02-28T21:21:04Z

Maybe the renaming is associated with the minecart but not with the command block...

marcono1234 2014-05-31T16:08:58Z

Confirmed for 14w21b
Maybe relates somehow to: MC-56132

marcono1234 2016-02-19T13:24:50Z

Confirmed for

1.9-pre2

MC-54777 is a duplicate of this report.

15 more comments

marcono1234 2016-02-19T14:35:45Z

Please link to this comment in the description

The following is based on decompiled version of Minecraft 1.8 using MCP. All method and class names are the names used in the decompiled version.

The reason why this happens is that objects of the net.minecraft.entity.EntityMinecartCommandBlock.EntityMinecartCommandBlock class have a net.minecraft.command.server.CommandBlockLogic object to be able to run commands. All entities have the CustomName tag however this class has a CustomName tag as well that is used for the name of the command block that is displayed when a command is executed. When a command_block_minecart item is placed on a rail, only its CustomName that all entities use is set, however not its CustomName used for commands. Once the entity is saved, the CustomName used for commands overrides the CustomName that all entities use. As the first one (that is used for commands) was never set to the custom name, it saves the default name "@".