Bug Can't use IAspect Lookup inside an IJobEntity

Goal
Be able to lookup other entities IAspect from inside an IJobEntity.

Tentative

Here is a sample of what I tried:

Code (CSharp):

1.  
2. public readonly partial struct DemoAspect : IAspect
3. {
4.     public readonly Entity entity;
5.     public readonly RefRO<Translation> Translation;
6. }
7.  
8. public partial struct DemoSystem : ISystem
9. {
10.     public void OnCreate(ref SystemState state)
11.     {
12.     }
13.  
14.     public void OnDestroy(ref SystemState state)
15.     {
16.     }
17.  
18.     public void OnUpdate(ref SystemState state)
19.     {
20.         // OK:
21.         var translationLookup = state.GetComponentLookup<Translation>(isReadOnly: true);
22.         new DemoJobWithComponentLookup() { lookup = translationLookup }.Run();
23.  
24.         // Getting error SGJE0009: DemoSystem.DemoJobWithAspectLookup contains non-value type field lookup.
25.         var demoAspectLookup = new DemoAspect.Lookup(ref state, isReadOnly: true);
26.         new DemoJobWithAspectLookup() { lookup = demoAspectLookup }.Run();
27.     }
28.  
29.     private partial struct DemoJobWithComponentLookup : IJobEntity
30.     {
31.         public ComponentLookup<Translation> lookup;
32.  
33.         public void Execute(Entity entity, in Parent parent)
34.         {
35.             var lookupedUp = lookup[parent.Value];
36.         }
37.     }
38.  
39.     private partial struct DemoJobWithAspectLookup : IJobEntity
40.     {
41.         public DemoAspect.Lookup lookup;
42.  
43.         public void Execute(Entity entity, in Parent parent)
44.         {
45.             var lookupedUp = lookup[parent.Value];
46.         }
47.     }
48. }
49.  

But I failed to make it work at the moment. It get the following error:

SGJE0009: DemoSystem.DemoJobWithAspectLookup contains non-value type field lookup

But, the Lookup is a value-type, so it looks like a code gen bug where the autoGen Lookup for an IAspect is not detected as a value-type, as well all it's fields.

Question

What would be the best workaround at the moment to use the aspect lookup inside a Job?

I tried to do create new Aspect, but the generated constructor is private (var lookup = new DemoAspect(entity, TranslationComponentLookup.GetRefRO(entity)).

I also tried to use the CreateAspect, but this requires the SystemState (which is a ref struct), so it cannot be passed to a IJobEntity (would require ref partial struct DemoJobWithAspectLookupWorkaround : IJobEntity, but you cannot be an ref struct AND implement an interface at the same time). And we also cannot use NativeReference<SystemState>.

The best I came out with is to add a static helper method into the IAspect and do the same thing as the IAspect.Lookup does, but it does requires me to keep all the refs to all the required Lookups (in my real secenario, I have up to 7), which is quite annoying:

Code (CSharp):

1.  
2. public readonly partial struct DemoAspect : IAspect
3. {
4.     public readonly Entity entity;
5.     public readonly RefRO<Translation> Translation;
6.  
7.     public static DemoAspect DemoAspectWokaround(Entity entity, RefRO<Translation> translation)
8.     {
9.         return new DemoAspect(entity, translation);
10.     }
11. }
12.  
13.     private partial struct DemoJobWithAspectLookupWorkaround : IJobEntity
14.     {
15.         public ComponentLookup<Translation> lookup;
16.  
17.         public void Execute(Entity entity, in Parent parent)
18.         {
19.             var lookupedUp = DemoAspect.DemoAspectWokaround(parent.Value, lookup.GetRefRO(parent.Value));
20.         }
21.     }
22.  

So, better ideas?

 

It's weird that

TransformAspect.Lookup

doesn't generate the SGJE0009 error, but custom Aspects do.

Because it most certainly is a bug, my temporary workaround is just to copy the codegen'ed Lookup implementation into my own IAspect struct, and rename "Lookup" into something else. Seems to work well for me so far. Just need to remember to re-copy whenever the code changes.

 

Yeah I think this is a bug. Especially since TransformAspect.Lookup appears to work like @Singtaa mentioned. The DemoAspect.Lookup type is a value type, so I think codegen is just tripping up on this for some reason.

 

I confirm that if I copy/paste the Lookup auto-gen code in my own class that I don't have the issue. It will be a OK workaround for now as I won't have to change the architecture of the project.

 

It seems to still be the case in 1.0.0-pre.15

 

While not ideal, this worked for me, thanks.

 

FYI, after updating to EditorVersion: 2022.2.8f1 with "com.unity.entities": "1.0.0-pre.44" the original issues is now fixed! (and note that the above workaround no longer works)