Snapshot 13w25c, Minecraft 1.6.2, Minecraft 14w20b, Minecraft 1.8-pre1, Minecraft 1.8.3, Minecraft 1.8.6, Minecraft 15w44a, Minecraft 1.9.4, Minecraft 1.10.2, Minecraft 1.11, Minecraft 1.11.2, Minecraft 1.12 Pre-Release 6, Minecraft 1.12 Pre-Release 7, Minecraft 1.12, Minecraft 1.12.1 Pre-Release 1, Minecraft 1.12.1, Minecraft 1.12.2 Pre-Release 1, Minecraft 1.12.2 Pre-Release 2, Minecraft 1.12.2, Minecraft 17w43a, Minecraft 17w43b
Certain block entities, when newly placed next to a power source, won't activate until they receive a block update.
Steps To Reproduce:
1. Place a command block to where it will be powered as soon as it is placed.
2. Type a command into the command block, e.g.: "say test".
> Notice the command block won't output "test" although it's powered.
3. Cause a block update next to the command block.
> Notice the command block now outputs "test".
This also occurs with dispensers, droppers, and note blocks.
MC-51340, it also happens if you got certain block entities with NBT data (e.g. a command block with an inserted command) and place that manually next to a power source, as well as
MC-31100 if you setblock certain block entities with NBT data where they would get powered, as well as
MC-80901 as falling block.