While the running server will still be using the recently introduced
copy-mechanic for vanilla command namespacing, the data converter logic
relies on the fact that namespaced aliases were redirects as well.
To not break the converted, the commands type now takes a modern flag
only set by the running server.
While the paper command system no longer uses redirects for namespaced
registration, vanilla still does. This means that removal of vanilla
redirecting target nodes still causes issues, e.g. the removal of the
vanilla 'msg' node in favour of a command alias one.
Redirecting nodes like tell, minecraft:msg and minecraft:tell are broken
by this and need to by flattened before sending them to the client.
This method was used pre 1.17 era where an Entity was explicitly
tied to a (then called) Chunk's entity slices. If an entity
was not inside a Chunk, then it was considered invalid as
it was not possible to save the entity.
In 1.17+, entities are now tied to a separately tracked entity
section management system. This system is far more reliable now
as it no longer requires a full chunk load to properly track
entities for saving. As a result, an Entity if inside the world
is always attached to some entity chunk section (except in rare
cases in Vanilla which are fixed in Moonrise).
As a result, whether the chunk the entity is in is loaded is no
longer an indication of whether they are tracked in the world
and we can reliably infer that the entity is correctly in the
world through the valid field alone.
Additionally drop the isInWorld() check, as valid=true implies
isInWorld=true. More importantly, the isInWorld() check invokes
getHandle which may trip a thread check on Folia. This will fix
World#getEntities() and friends exploding on Folia.
However, World#getEntities() on Folia still cannot reliably return
all entities in the world as actions such as cross-region
(not cross-world) teleporting will remove entities from the world.
Epic