readonly is WriteOnly?

I've been experimenting with the ECS today and seem to have discovered a bug involving the C# readonly keyword and the Job system safety checking. Apologies if this isn't the right place to make a bug report.

I've created this fairly trivial system which simply runs through some input components, calculates a value from them and writes it to an output component (all inside a job). This is fine except that the _inputs field is only written to in the constructor, so as is usually good practice I marked it as readonly. I guessed this might even implicitly mark the field as [ReadOnly] for me which would be convenient.

Instead I get this error (only when the _inputs field is readonly):

InvalidOperationException: The native container has been declared as [WriteOnly] in the job, but you are reading from it.
​

Here's an excerpt from the stacktrace:

Unity.Entities.ComponentDataArray`1[T].get_Item (System.Int32 index) (at ComponentDataArray.cs:99)
LightBulbPostSystem+AfterPower.Execute (System.Int32 index) (at LightBulbComponent.cs:76)
​

Which shows it is happening on this line:

var supply = _inputs[index].PowerSupplied;
​

So the stacktrace makes sense, I am getting an item on this line. The safety check is even semi correct - I am reading from the field, but I never marked anything as WriteOnly!

Why does adding readonly cause this?

 

Did you ever figure this out? I'm getting the same issue.

 

I had the same issue a while ago.


Removing the readonly modifiers (not the attributes) resolves the problem.

 

I can't manage to replicate the problem now. Putting my gist example into a project doesn't produce it. I tried making the change to a similar system in the real project and it doesn't break either (although I've made fairly significant changes to the real project since the prototyping stage). If I encounter the problem again I'll try to replicate it in a smaller project.

 

Can't reproduce it either. It's probably fixed by now.

 

Reproduced. Case 1085026.

 

Thanks! We'll take a look

 

Is there any update on this?

I'm getting this error while scheduling a job (ie: JobParallelFor1) where I pass a ArchetypeChunkSharedComponentType<SharedComponentX> where SharedComponentX is being read on another job (ie: JobParallelFor2). Note that I just pass it and schedule the job, the job (JobParallelFor1) has no logic and it will throw the error.

InvalidOperationException: The native container has been declared as [WriteOnly] in the job, but you are reading from it.

This error will point to the line where SharedComponentX is being read in the job (JobParallelFor2).

 

If you use Injection to read a SharedComponent from a job and use Chunks on another job it will trigger the error. Using Chunks for both jobs fixed the problem.

 

Glad to hear you found a workaround for the time being! We unfortunately haven't had a chance to dig into this (or several other issues) due to Unite being right around the corner, but we'll be working through the backlog afterward.

 

You are doing far too many Unites. One in Europe is enough.

 

Had the same Bug. I created a NativeList inside of a jobs method and trying to access it via enumerator. This results in this strange exception. Solved it by using ToArray(allocator) instead...

 

I seem to have the same problem as StefanWo above. I have an editor tool script where I run a job like this_

Code (CSharp):

1. var testJob = new TestJob();
2. testJob.Schedule().Complete();

Inside the job there is a method with a local NativeList.
Running this code gives me the error "InvalidOperationException: The Unity.Collections.NativeList`1[System.Int32] has been declared as [WriteOnly] in the job, but you are reading from it." when I Add() items to the local NativeList:

Code (CSharp):

1.  
2.     public struct TestJob : IJob
3.     {
4.         public void Execute()
5.         {
6.             var list = new NativeList<int>(Allocator.Temp);
7.             for (int i = 0; i < 10; i++)
8.             {
9.                 list.Add(i);
10.             }
11.  
12.             DoLoop(list);
13.         }
14.  
15.         private void DoLoop(NativeList<int> passedInList)
16.         {
17.             var localList = new NativeList<int>(Allocator.Temp);
18.             foreach (var item in passedInList)
19.             {
20.                 Debug.Log($"DoLoop {item}");
21.                 localList.Add(item);
22.             }
23.         }
24.     }
25.  

Doing a passedInList.ToArray() at the foreach makes the error go away.