ForkJoin | ForkJoinPool vs ThreadPoolExecutor benchmarks | Code Editor library

Judging by the name of your service methods, I'd assume that you actually wanted to use zip which emits after all Observables emit, instead of forkJoin which will only emit once all source observables complete.

Also, keep in mind that every observable needs a subscriber in order to emit anything. So, make sure that you actually subscribe to the result of hasPermissionsForX().

zip

forkJoin

You can try something like the following:

tap executes the function and then emits whatever it received, unchanged.

throwError is a function that returns an observable.

So, someObservable.pipe(x) will return an observable that emits an error if x is

• map(() => { throw new Error('msg') }), or

• switchMap(() => throwError('msg'))

... or you can simply create a new observable with throwError('msg')) and there's no need to pipe anything...

but tap(() => anything) won't change what the observable emits.

From ForkJoinPool

...All worker threads are initialized with Thread.isDaemon() set true.

From Executors.defaultThreadFactory

...Each new thread is created as a non-daemon thread.

From Thread.setDaemon

...The Java Virtual Machine exits when the only threads running are all daemon threads.

In the first case, the thread is coming from ForkJoinPool.commonPool and hence it is daemon.
And in the second case, the thread is created using Executors.defaultThreadFactory, so is non-daemon.

This explain the different behaviour.

Sounds like you need combineLatest:

Apparently, the author of the code is not creating folders programmatically in the code. So creating two empty directories as "tmp/arrf" in the base directory of the sbt project worked.

From the perspective of the task error, it is just because there are no resources, which is different from the other problem mentioned in the feedback.

Maybe you can reduce the parallelism and have a try

The documentation on trait parameters only mentions trait parameters, not trait constructors:

Scala 3 allows traits to have parameters, just like classes have parameters.

It also links to the original SIP document for reference:

For more information, see Scala SIP 25.

In the SIP-25 – trait parameters, it says [bold emphasis mine]:

In the ClassDef of traits, we still do not allow secondary constructors.

However, this restriction, is not reflected in the Syntax Summary, which does not actually distinguish between classes and traits syntactically. So, the restriction is purely one of documentation, not syntax specification.

So, to answer your question:

Why?

Because your code is syntactically valid but semantically invalid, and ScalaMeta seems to not expect this specific kind of semantic invalidity.

And why is it after line 1, which seems perfectly fine and gets accepted when I remove the rest? Does "invariant failed" mean that it's a bug in the compiler? (Many other compilers in such cases add to the message an encouragement to report it.)

It's clearly not a bug in the compiler since the exception is not thrown in the compiler, it is thrown in ScalaMeta.

Main questions:

• Are secondary (or auxiliary – IIUC the two terms I've seen used apparently interchangeably mean the same) constructors allowed in traits?

No. SIP-25 clearly disallows them.

As established in comment, BehaviorSubject emits the initial value in the resolver, because it takes some time for the http-request to complete, but by then, when new value would be emitted, the resolver has already done its job.

Looks to me that you wouldn't need the behaviorSubject as a middleman? You could assign it directly to an observable. If you need to share same data, you can use shareReplay which just emits the value without making a http request. So something like this for the country service: