How to use RegisterGenericSystemTypeAttribute?

[sage prawn]

I'm quite puzzled by the current support of generic ISystem. Even if I put a constraint where T : unmanaged, IComponentData on the system, T still:

1. Can't be used in SystemAPI.QueryBuilder().WithAll<T>()
2. Can't be an argument of IJobEntity.Execute

Then how generic ISystem could be a practical thing?

[storm hull]

um. why would you want a system to be an argument to a job

but @tidal dawn for the #1 part

unless you mean that T can't be an argument to IJE execute, in which case i guess that would maybe be the same bug

[tidal dawn]

That would be correct. Today generic ISystem would be SystemState, EntityManager, ECBs, Lookups etc. But no SystemAPI.Query.*/ SystemAPI.QueryBuilder.** and scheduling IJE. This being said, rest of SystemAPI should work with system level generics already today! Meaning all the API described here:
https://docs.unity3d.com/Packages/com.unity.entities@1.0/manual/systems-systemapi.html#access-data
:3

[storm hull]

curious, do generic systembase's work with those things?

i would think they'd be pretty similar

[tidal dawn]

Same rules on SystemBase and ISystem

[storm hull]

ah ok, i feel less bad then

[tidal dawn]

The remaining difference in sourcegen was fixed with your Generic ISystem support 😉

You have no idea how much code that cleaned up 😆

[sage prawn]

So for generic ISystem, I have to use IJobChunk instead of IJE, along with Lookups to retrieve generic component data?

That seems a lot of work just to make a working generic system.

Btw, should we have 1 or 2 examples for generic system? The document doesn't exist except that changelog so that's why I'm being confused about how practical generic system might be.

[sage prawn]

Yes, I mean the T component, not the system.

[storm hull]

As you can see, we aren't super convinced that generic systems in general, managed or unmanaged, should be at the top of our priority list. I just implemented them because everybody was yelling about how generic systembase's worked and generic isystem's didn't. We might get around to fixing the codegen stuff for it, since it's true it's not fun to do stuff without that. I'd be pretty surprised if we came out with a sample for them though.

[sage prawn]

It's alright if you can just fix the codegen.