The bug

As the title says, when attempting to create a moving_piston block, the block entity is not created.

How to reproduce

1. Type

   setblock ~ ~ ~ minecraft:moving_piston

   → Now the command can be run without NBT data
   → See it also suggests adding NBT data by suggesting the { character

2. Finish the command:

   setblock ~ ~ ~ minecraft:moving_piston{blockState:{Name:"minecraft:piston_head",Properties:{facing:"south",short:"false",type:"normal"}},facing:3,progress:0.0f,source:1b,extending:1b}

   → It says the block has been placed, but there's nothing visible

3. Type

   /data get block ~ ~ ~

   → It says the target block is not a block entity, and using the previous command in the same spot says it could not set the block. Note: using that same command on a moving block created by a piston does return the block entity

Affected methods

• setblock
• fill
• clone
• structure loading

Code analysis

Using MCP 1.12 names:

The tab-complete suggestion for NBT data occurs due to net.minecraft.block.Block.hasTileEntity() method returning true for the net.minecraft.block.BlockPistonMoving block. However, the block entity itself is not created because net.minecraft.block.BlockPistonMoving.createNewTileEntity() returns null.