Block age gets updated even after cancelling BlockGrowEvent

[bilektugrul]

Expected behavior

The block age must not get updated and must stay the same, same as before the grow.

Observed/Actual behavior

Cactus age still gets updated even after cancelling grow event.
Cactus is at age 0 -> BlockGrowEvent triggered -> Cactus is at age 1 -> Cancelling the grow event -> Cactus is still at age 1

Steps/models to reproduce

Make a cactus farm, size don't really matter.
Create a command that sends targeted block's block data.
Listen to BlockGrowEvent, maybe filter it to just cactuses.
Cancel the event.
Set the random tick speed gamerule high to test faster.
Use the command to see cactuses' datas. They'll have 15 age with just root block.

Plugin and Datapack List

[21:14:00 INFO]: ℹ Server Plugins (17):
[21:14:00 INFO]: Paper Plugins (3):
[21:14:00 INFO]: - FancyNpcs, RoseStacker, SkBee
[21:14:00 INFO]: Bukkit Plugins (14):
[21:14:00 INFO]: - Essentials, FastAsyncWorldEdit, Lands, LuckPerms, NBTAPI, packetevents, PlaceholderAPI, ProtocolLib, Skript, skript-reflect
[21:14:00 INFO]: uxmFarmer (my plugin), Vault, ViaBackwards, ViaVersion

Paper version

[21:13:53 INFO]: This server is running Paper version 1.21.10-129-ver/1.21.10@3e25649 (2025-12-19T23:34:30Z) (Implementing API version 1.21.10-R0.1-SNAPSHOT)
You are running the latest version

Other

I'm not sure if this is intented or not, I'm not saying it must be fixed right now but it really is weird and shouldn't happen. A person from Paper discord said the age data changes before BlockGrowEvent so its not really that event's fault, then there should be another event for this.
Please atleast discuss this. Also, not yet tried with other blocks like sugar cane and bamboo. Will try.
Also, also, happy new year!

[Doc94]

Hi, try check in 1.21.11 based in the code the logic its..

• Cactus get age 15
• Cactus need to grow one block above
• Call the BlockGrowEvent
• If its cancel ignore the rest of logic for set block and set the new age (the age its only change if its less than 15)

The rest of changes in age not call that event (the grow cactus flower but that is in age 8 with other conditions) then i feel is intented based in vanilla logic.. if cancel the grow the age its already 15 then cancel that not change any.

[electronicboy]

The grow event fires for the cactus growing into the block above it, not for the cactus itself; cancelling the flower growth will still cause the logic for the block to age, cancelling for the cactus growth will prevent the rest of the logic in that block from running, but, that is all placement of the new block logic (and the aging logic for the current cactus block, but, that won't do anything as it's already max age in that state)

for the cactus, there would need to be two event fires to fix this, one being the forming of a new block, and the other being the self state update; I semi recall this event being fairly inconsistent in terms of a contract over what "grow" means

[bilektugrul]

The grow event fires for the cactus growing into the block above it, not for the cactus itself; cancelling the flower growth will still cause the logic for the block to age, cancelling for the cactus growth will prevent the rest of the logic in that block from running, but, that is all placement of the new block logic (and the aging logic for the current cactus block, but, that won't do anything as it's already max age in that state)

for the cactus, there would need to be two event fires to fix this, one being the forming of a new block, and the other being the self state update; I semi recall this event being fairly inconsistent in terms of a contract over what "grow" means

So as far as I understood, cancelling the BlockGrowEvent does not prevent the cactus from aging because thats not where the event triggers, it gets triggered after Cactus reaches maximum age thats why I cannot prevent aging of the root cactus. Also then there is the flower which gets placed when Cactus reaches age 8 and triggers the grow event with Cactus Flower block inside it.

If we had a BlockAgeChangeEvent thats cancellable, I think that would solve the issue without breaking plugins that are using BlockGrowEvent. Also, sugar canes would benefit from such event if added. If that seems a bit too much, BlockGrowEvent getting triggered for each age of each block that calls it would be good and consistent.

I think bamboos are different, cancelling the spread event prevents them from aging.

(Originally I thought BlockGrowEvent was triggering for each age state but I was wrong, so I edited this comment)