Datapacks modifying nether/end generation don't apply properly

[Virenbar]

Expected behavior

Flat terrain to be generated.

Version: Paper-325

Observed/Actual behavior

Normal terrain generated.

Version: Paper-377

Steps/models to reproduce

1. Add datapack to <world>\datapack and enable it.
2. Restart server.
3. Generate new terrain.
4. Normal terrain generated instead of flat.

Datapack: FlatOverworld.zip
This datapack makes terrain in overworld flat.

Plugin and Datapack List

> plugins
[23:58:58 INFO]: Plugins (0):
> datapack list
[23:59:18 INFO]: There are 3 data packs enabled: [vanilla (built-in)], [file/bukkit (world)], [file/FlatOverworld (world)]
[23:59:18 INFO]: There are no more data packs available

Paper version

> version
[23:57:24 INFO]: This server is running Paper version git-Paper-377 (MC: 1.17.1) (Implementing API version 1.17.1-R0.1-SNAPSHOT) (Git: 3f17694)
You are running the latest version
Previous version: git-Paper-325 (MC: 1.17.1)

Other

Server was updated from paper-325 to paper-377 and datapack stopped working.
Datapack works in vanilla server.

[Virenbar]

Tested other versions. Paper-335 is latest version in which datapack works.
In version 336 datapack has stopped working. It seems PR #6789 broke something.

[jpenilla]

Tested other versions. Paper-335 is latest version in which datapack works. In version 336 datapack has stopped working. It seems PR #6789 broke something.

Just re-tested, and

• Datapacks adding custom dimensions work in Paper 335 and Paper 336
• The datapack linked in the original issue (https://github.com/PaperMC/Paper/files/7515357/FlatOverworld.zip) works in singleplayer, but not on a vanilla server, Paper 335, or Paper 336

It seems like this issue is unrelated to custom dimensions and #6789, but is instead an issue with the vanilla server relating to loading datapacks which modify overworld generation.

[Virenbar]

Also re-tested.
All servers were started with datapack enabled and empty ".\world\region" folder.

Screenshots

Vanilla server - Works

Paper-335 - Works

Paper-336 - Not working

Paper-master without 0826-Use-correct-LevelStem-registry-when-loading-default-.patch - Works

[jpenilla]

Something is definitely wrong with your testing setup. Creating a new directory with just server.jar from mojang's site, world/datapacks/FlatOverworld.zip, and eula.txt with eula=true results in the datapack not working. I was unable to get the datapack to successfully modify overworld gen anywhere except singleplayer by adding the datapack from the world creation menu.

In my testing, the vanilla server, Paper 335, Paper 336, Paper master, and paper master with the aforementioned patch reverted all resulted in the same behavior in regards to the datapack not modifying overworld gen from a clean server. I understand you claim otherwise, but before anyone on the team spends any more time on this I think we need confirmation from someone else that this ever worked, as like I already said my testing strongly implies this is a vanilla issue.

[Virenbar]

Here a short video of testing on vanilla server (server.jar, eula.txt, ops.json, startmc.bat with Aikar's Flags)

[Machine-Maker]

maybe the disconnect here is that you are only deleting the region file. when I tested, I deleted everything in the world except the datapacks folder, so the first generation would be with the datapack enabled, but maybe that doesnt work

[Virenbar]

Enabled datapacks saved in level.dat, deleting it disables all datapacks.

[Machine-Maker]

yeah, but all not-recognized datapacks are autoenabled upon server start