[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.

Related issues

is duplicated by

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

MC-136611 Minecart with Command Block changing its name

relates to

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

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

Attachments

MC-32701.mp4

Comments

migrated 2013-09-26T17:50:24Z

[media][media][media]

migrated 2013-09-30T14:50:24Z

Confirmed.

migrated 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.

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 "@".

wobst.michael 2018-01-16T20:50:51Z

This has been fixed partly. It now outputs its name, but defaults back to @ after re-login.

migrated 2020-05-26T18:36:57Z

~~seems fixed~~

marcono1234 2020-05-28T20:13:07Z

No, this issue still occurs in 20w21a

migrated 2020-06-25T00:24:11Z

Affects 1.16.1

pulpetti 2020-07-06T18:34:05Z

Affects 1.16.1 and 20w29a

pulpetti 2020-08-07T08:15:55Z

In 1.16.2 Pre-3

Avoma 2020-12-23T11:16:40Z

Can confirm in 20w51a.

Avoma 2021-01-28T14:57:56Z

Can confirm in 21w03a.

Avoma 2021-02-06T12:20:30Z

Can confirm in 21w05b.

Avoma 2021-02-12T13:44:24Z

Can confirm in 21w06a.

Avoma 2021-02-19T10:57:02Z

Can confirm in 21w07a. Video attached.

migrated 2021-05-06T13:18:55Z

Affects 21w18a

migrated 2021-06-09T12:11:28Z

Affects 1.17

Avoma 2021-07-13T12:51:05Z

Can confirm in 1.17.1.

migrated 2021-10-12T19:39:55Z

Affects 21w40a

Avoma 2022-01-02T17:13:54Z

Can confirm in 1.18.1.

Avoma 2022-05-10T16:51:57Z

Can confirm in 1.18.2 and 22w18a.

Avoma 2022-06-19T10:35:30Z

Can confirm in 1.19 and 22w24a.

migrated 2024-10-13T11:00:48Z

Cannot reproduce in 1.21.2 Pre-Release 3
Tested with experimental minecart improvements datapack enabled.