Polymer + ViaFabric 1.20.4 seems to not omit experimental mobs, blocks, items for Fabric 1.20.2 clients

[Ampflower]

/viaversion dump Output

https://dump.viaversion.com/192aa3afd02a621ab569400d1c62c30f07963758c2f8c0a477999b3ac5d9b7b0

Console Error

From server - not particularly helpful for more than versions

From client

Bug Description

Fabric 1.20.2 clients cannot join a ViaFabric 1.20.4 server due to registry syncing.

Note, duplicated this issue from Patbox/polymer#109, originally reported on Modflower/Polysit#7.

Steps to Reproduce

• On server:
  • Use Minecraft 1.20.4
  • Install Fabric API, ViaFabric, ViaRewind, Polymer, any Polymer-based mod (i.e. Polysit, Polyfactory)
    • It seems that any registry modification is required, as bare Polymer doesn't trip the bug.
• On client:
  • Use Minecraft 1.20.2
  • Install Fabric API; the vanilla client seems unaffected
• Start the server with the given mod set
• Join the server

Expected Behavior

As a vanilla client would do; join perfectly fine

Additional Server Info

No proxies were used; same computer and directly connected via [::] on Linux (equivalent to [::1])

Checklist

• [X] I have checked if this is specific to ViaFabric platform, and doesn't happen when running it on other platforms (Paper/Sponge/Velocity/Waterfall).
• [X] I have included a ViaVersion dump.
• [X] If applicable, I have included a paste (not a screenshot) of the error.
• [X] I have tried the latest build(s) from https://ci.viaversion.com/ and the issue still persists.

[Ampflower]

As Kichura has asked for; the packet, if you just want to outright disable it, is fabric:registry/sync/direct via CustomPayloadS2CPacket (extracted via Gadget), which appears to be during the configuration/pre-play phase.

I'd recommend seeing if it's possible to omit the individual version-specific entries if possible in the very unlikely case of someone trying to do multiversion with an actual modpack; tho realistically that's likely more fit for ViaFabricPlus than it is here.

[Kichura]

Update on this:

Polymer somehow works again on 1.19.1, 1.19.2, 1.19.4, 1.20/1.20.1 and 1.20.3/1.20.4 again including 1.20.5/1.20.6 but not 1.19.3 and 1.20.2 meaning progress is somehow being made.

[Kichura]

Update 2: We got the thing working at last with a silly workaround whilst all of this time, it felt like i was doing a quest.

[Kichura]

The setting has been merged meaning this is now resolved, to use the feature - Open up the ViaFabric config and set ignore-registry-sync-errors to true.

[ArkoSammy12]

The setting has been merged meaning this is now resolved, to use the feature - Open up the ViaFabric config and set ignore-registry-sync-errors to true.

Im glad to see this issue being resolved after 4 months of my original issue report on Polysit's repo, thank you.

One last thing. Are there any downsides to enabling ignore-registry-sync-errors that I should be aware of?

[FlorianMichael]

It basically disables Fabric's validation of registries, doing so may cause unexpected issues which would have gotten a proper error message before, but other than that you should be fine. Sorry for the wait.

[ArkoSammy12]

It basically disables Fabric's validation of registries, doing so may cause unexpected issues which would have gotten a proper error message before, but other than that you should be fine. Sorry for the wait.

No worries, and thank you for the answer 👍