Line break is added when using newlines.source = keep with a trailing comment

[domagojlatecki]

Configuration

version = "3.8.6"

runner.dialect = "scala3"

newlines {
  source = keep
}

Command-line parameters

When I run scalafmt via CLI like this: scalafmt -c .scalafmt.conf src/app/main/scala/Snippet.scala

Steps

Given code like this:

val _ = println( //
  x = "string"
)

Problem

Scalafmt formats code like this:

val _ =
  println( //
    x = "string"
  )

Expectation

I would like the formatted output to look like this:

val _ = println( //
  x = "string"
)

Workaround

Versions prior to 3.8.4 do not have this problem. Removing newlines.source = keep fixes the issue, but it formats other things differently.

Notes

The trailing comment in the example above is a workaround I have been using to avoid this kind of formatting:

val _ = println(x =
  "string"
)

This case is caused by optIn.configStyleArguments = false which I use.