Runtime: use Internal abstract class to make unsafe a val
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- Add a prettified `toString` method to render the Runtime Before: ``` scala> zio.Runtime.default val res0: zio.Runtime[Any] = zio.Runtime$$anon$3@22824450 ``` After: ``` scala> zio.Runtime.default val res1: zio.Runtime[Any] = Runtime(environment = ZEnvironment(), fiberRefs = FiberRefLocals(), runtimeFlags = RuntimeFlags(Interruption, CooperativeYielding, FiberRoots)) ```
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hearnadam
commented
Nov 23, 2025
Comment on lines
+218
to
+221
| override def unsafe: UnsafeAPI with UnsafeAPI3 = { | ||
| if (unsafe0 eq null) unsafe0 = new UnsafeAPIV1 {} | ||
| unsafe0 | ||
| } |
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This is unfortunately necessary as directly instantiating a val can cause issues with the order of instantiation:
error: scala-k8s.md:101:1: Cannot invoke "zio.FiberRef.initial()" because "fiberRef" is null
val nodes = ZIOKubernetesClient.send(APIs.nodes.list())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
java.lang.ExceptionInInitializerError
at zio.FiberRef$.<clinit>(FiberRef.scala:599)
at zio.ZIO$ServiceWithZIOPartiallyApplied$.apply$extension(ZIO.scala:5722)
at zio.ZIO$ServiceWithPartiallyApplied$.apply$extension(ZIO.scala:5711)
at zio.ZIO$.service(ZIO.scala:4750)
at dev.hnaderi.k8s.client.ZIOKubernetesClient$.send(ZIOKubernetesClient.scala:30)
at repl.MdocSession$MdocApp.<init>(scala-k8s.md:17)
at repl.MdocSession$.app(scala-k8s.md:3)
Caused by: java.lang.NullPointerException: Cannot invoke "zio.FiberRef.initial()" because "fiberRef" is null
at zio.FiberRefs.getOrDefault(FiberRefs.scala:150)
at zio.Runtime$UnsafeAPIV1.<init>(Runtime.scala:125)
at zio.Runtime$$anon$3$$anon$4.<init>(Runtime.scala:245)
at zio.Runtime$$anon$3.<init>(Runtime.scala:245)
at zio.Runtime$.apply(Runtime.scala:241)
at zio.Runtime$.<clinit>(Runtime.scala:254)```
kyri-petrou
reviewed
Nov 24, 2025
| new UnsafeAPIV2 {} | ||
|
|
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| override def unsafe: UnsafeAPI with UnsafeAPI2 with UnsafeAPI3 = { | ||
| if (unsafe0 eq null) unsafe0 = new UnsafeAPIV2 {} |
Contributor
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Don't we need to cache this? We could unsafely set the type of unsafe0 to Object (which is what UnsafeAPI with UnsafeAPI2 with UnsafeAPI3 is compiled to anyways)
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What do you mean cache this? that's what the assignment is doing?
Contributor
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I did not read it correctly, nevermind me 🤦
kyri-petrou
approved these changes
Nov 28, 2025
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I noticed that in libraries that use
Runtime.unsafeto create Fibers, the Unsafe allocation can actually be non-trivial. This change introduces a new abstract class to cache an instance in a var. I initially used aval, but ran into some class instantiation issues.I added a prettified
toStringmethod to render the RuntimeBefore:
After: