CommandBuffer Pending Entity

[martindevans]

As briefly discussed in Discord, this modifies the CommandBuffer to not return fake Entity objects. Instead it returns a PendingEntity. This makes the API less confusing and prevents all the mistakes you could make.

Added a new test ("CommandBufferEntityErrors") which demonstrates all the possible errors this fixes:

• Using the returned Entity with the world (fails type checking)
• Creating an entity with one buffer, using it with another buffer (throws)
• Creating an entity, calling playback, then trying to use the entity with this buffer (throws).

Breaking Change

Note that this is a breaking change: The Create() -> Entity method has become Create() -> PendingEntity.

Most code that is broken by this should either be extremely easy to fix (just change the type) or was already subtly broken and this more explicit break is a good thing.

[martindevans]

To be honest I don't really like the name PendingEntity, but couldn't think of anything better.

[genaray]

Thanks! Im gonna look at that one later ^^
Just wonder if there any drawbacks to this. E.g. having an PendingEntity might be a bit restrictive in certain scenarios. Im gonna check that

[martindevans]

I don't think there's anything that is valid to do with the "Entity" returned by the CommandBuffer that the PendingEntity doesn't allow. If you do identify something a use-case I've missed I'll add something to support it.

[Shelim]

Bumping the PR - it would make desired usage of value returned from CommandBuffer so much cleaner and much less prone to human errors. Even the docs currently does not specify what is allowed with returned value and - for me example - it was easy to (wrongly) believe I can use the value as standard entity identifier after executing all commands from the buffer.