Blocks were being overwritten in the writebatch which hadn't yet been set, so reading them from the world yielded air blocks instead of trunk, allowing the generation to overwrite blocks which should have been logs.
This prevents plugins sending wrong packets at the compiler level (or would, if we had a compiler). It's more robust than a getter for client/server and throwing an exception since a static analysis tool can detect faults created by sending wrong packets from the server. This is also used to deny service to dodgy clients which send wrong packets to the server to attack it.
this is in preparation for clientbound/serverbound packet separation. I did this already on another branch, but the changeset was dependent on a massive refactor to split apart packets and binarystream which i'm still not fully happy with.
Encoded tags larger than 32KB overflow the length field, so we can't send these over network. However, it's unreasonable to randomly throw this burden off onto users by crashing their servers, so the next best solution is to just not send the NBT. This is also not an ideal solution (books and the like with too-large tags won't work on the client side) but it's better than crashing the server or client due to a protocol bug. Mojang have confirmed this will be resolved by a future MCPE release, so we'll just work around this problem until then.
This is a bolt-on feature that can't be disabled and causes serious grief for Unix server users, because it prevents ctrl+c aborting the server the normal way.
Instead, we prefer introducing a plugin to implement this functionality, so that users can opt-in or opt-out.
The only cyclic references here are both destroyed during normal collection directly (net interface removes from sessions array, player destroys its session reference), so there's no need to destroy them again here. This just causes a giant swathe of potential crashes for no real benefit.
close#2669
this has been a bug for a long long time. I think the reason it was never addressed is because of the performance impact associated with it. However, that performance impact is now gone thanks to light update batching.
this allows deduplicating block updates when lots of adjacent blocks are set on a tick, which has beneficial effects on performance. It also fixes#2659.
Future scope:
- Use this mechanism to deal with explosions properly.
- Don't execute block updates for air blocks.
future enhancements:
- make gamemode an object containing information about abilities that players have in this gamemode (gamemodes are just predefined ability sets)
- get the magic numbers out of the API
