Disabling the vanilla data pack disables certain game behaviors. This currently includes, amongst others:
Leaves start decaying
Anvils can't be opened
Marking maps with banners won’t work
Lava same color as water
See comment of @unknown in MC-129244:
...
The issue you are reporting now, which is specific to not loading vanilla datapack, is working as intended. If you do not provide a definition of what lava is, the client will not know and that is undefined behaviour. If you intend to replace vanilla datapack you must make your own definitions of things instead.
Linked issues
is duplicated by 50
MC-123191
all trees decy if one is broken while vannila datapack disabled
Resolved
MC-123246
Leaves decay reguardless of wood nearby when the "vanilla" datapack is disabled.
Resolved
MC-123262
Leaves decay even when attached to logs
Resolved
MC-123303
Tree's leaves disappears
Resolved
MC-123623
Leaves decay no matter what
Resolved
relates to 3
Attachments
Comments 9
It looks for anything matching block tag
minecraft:log. If you do not redefine this to your own needs, then the behaviour will be broken.
As more and more things get moved to data packs, the more behaviours you will be disabling by disabling vanilla. Sometimes this isn't desired so you will have to just redefine the exact behaviours you wanted.
I don't understand quite clearly. Other bugs refer as duplicates of this one. Those other bugs mention leaves decaying that shouldn't do so. I can confirm this too. When I import my 1.12.2 world in 18w22b, all the leaves that I've manually placed in the last 3 years have all decayed.
My vanilla data packs are not disabled either. The command "/datapack list enabled" returns "There are 1 data packs enabled: vanilla". Yet persistent leaves are still decaying.
also some missing game behaviors like water and lava physics, even with their fluid tags inside the custom datapack, still persist as of 1.13-pre8 without the vanilla datapack
I like this as a feature, but where/how do you define the physics of water and lava as well as their interactions results (cobblestone, stone, obsidian)? None of these interactions work with vanilla disabled. I would love to be able to redefine/customize the results of their interactions as well as their physics (like flow range) but I can't seem to figure out how to do this.
Still an issue in 1.14.4, I cannot seem to shoot a bow if the vanilla datapack is disabled. I'm sure that if I look around I could find more broken game behaviors...
Doesn't seem to need to be a lan world or server or need another datapack. After creating a world in 17w49b I just disabled the vanilla datapack and it started happening.