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MC-51340

Certain blocks do not update when falling, placed or cloned next to a power source

The bug

When certain block entities such as a dropper/dispenser or a command block that contain NBT data for items or a command is either placed manually on a power source or cloned on a power source it will receive power because a repeater gets power from the side of it but the dispenser will not place/drop anything and the command block will not run the command.

How to reproduce

  1. Place down a dispenser or dropper or command block

  2. Put items or a command into the block, depending what it is

  3. Control and middle-click the block to get the block with NBT data

  4. Place this on a power source such as a redstone torch or a redstone block
    โ†’ It should run the command or drop/place something but it does not

Note: this also affects note blocks, they won't play a note until they received a block update.

Test command for falling block, insert into a command block and trigger:

summon falling_block ~ ~2 ~ {
	BlockState:{Name:"minecraft:stone"},
	Time:1s,
	Passengers:
	[
		{
			id:"falling_block",
			BlockState:{Name:"minecraft:redstone_block"},
			Time:1s,
			Passengers:
			[
				{
					id:"falling_block",
					BlockState:{Name:"minecraft:command_block"},
					TileEntityData:{Command:"say Test"},
					Time:1s
				}
			]
		}
	]
}

Related issue

MC-31100 when using /setblock to place the block it does not update (and more)

Code analysis

Code analysis by @unknown can be found in this comment on bug report MC-18631.

Linked issues

MC-18631 Some redstone components (block entities) do not update themselves when placed Resolved MC-73882 Dispenser does not look for redstone power when placed Resolved MC-75576 Redstone Repeater Bug Resolved MC-80901 Landed Falling Block does not trigger redstone updates for block entities (Command Blocks, ...) Resolved MC-86663 Chain Command Block not powered by Redstone Block when Chain Block is placed next to or on a Redstone Block before being turned from Impulse to Chain. Resolved

Comments 19

gentlegiantJGC

This is still a problem but I feel like it is probably going to be marked as "Works as Intended"

Reopened, thanks.

Frank Steffahn

This behavior is somewhat useful as you can use command blocks as block update detectors

Confirmed for 1.12 pre-7.

Please consider what I wrote here.

I'm more than willing to take over all 4 bugposts or, preferrably, all of them bundled into the oldest one, if the OP regarding that type of problem (MC-18631) doesn't update it; I would also list all 4 test setups for bug reproduction into that one.

gentlegiantJGC

Meri if you would like to take over this bug post you are more than welcome to.
I am not sure what the process to go about transferring it is though

9 more comments
Giovanni Lanzarote

confirmed for 20w49a

Giovanni Lanzarote

Still an issue in snapshot 20W51A

Giovanni Lanzarote

Still an issue in snapshot 21w03a

Still an issue in 1.17.1.

Also affects items with BlockStateTagย when placed, even when that block is not a block entity, see this video.

Since this also affects blocks which are not block entities, such as composters and note blocks, I have updated the title to reflect this.

gentlegiantJGC

Meri Diana

(Unassigned)

Confirmed

Platform

Low

Commands

/clone, block-entity, block-update, command_block, dispenser, dropper, note_block, powered, redstone

Minecraft 14w11b, Minecraft 14w17a, Minecraft 14w18a, Minecraft 14w30b, Minecraft 14w30c, ..., 1.17 Pre-release 3, 1.17.1, 1.18.2, 1.19.1 Pre-release 5, 1.20.2

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