Compiler warnings do not appear in the output

[nrinaudo]

Given the following code:

```scala mdoc
def unwrap(oi: Option[Int]): Int = oi match {
  case Some(i) => i
}

I would expect the mdoc output to contain the non-exhaustivity warning, or to have a :warnings modifier of some sort to do so.

What I get instead is:

def unwrap(oi: Option[Int]): Int = oi match {
  case Some(i) => i
}

Note that there's an easy workaround, which is to make compiler warnings fatal and use :fail, but this might have other unwanted side effects.

[olafurpg]

Thanks for reporting! I'm able to reproduce the timeout, not sure what's going on here 🤔

[nrinaudo]

I believe this comment is on the wrong issue :)

[olafurpg]

Whoops, that comment was supposed to be for #124. Still, I'm able to reproduce.

It's not necessary to enable fatal warnings to print the warning, :fail also works when there are only warnings and produces the following output:

def unwrap(oi: Option[Int]): Int = oi match {
  case Some(i) => i
}
// warning: match may not be exhaustive.
// It would fail on the following input: None
// def unwrap(oi: Option[Int]): Int = oi match {
//                                    ^^

Is that an acceptable workaround? We could add a :warning modifier which fails only if there's a warning (not error), but I'd prefer to not introduce unnecessary modifiers when :fail already works.

With :fail it's not possible to evaluate the program however, is that necessary for your use case? I think it might be possible to support it but it's not straightforward how to implement it.

[nrinaudo]

In a way mdoc basically already considers warnings to be fatal, then?

I'm trying to think of scenarios where this wouldn't be acceptable. Maybe in documentation that demonstrates a bit of code that generates a warning, then uses that code to show the warning was correct?

I think in my case it's perfectly sufficient, but there will inevitably be someone down the line that'll need to have warnings output and still evaluate the program :)

[olafurpg]

Sounds good, let's close this issue then and let somebody else start a new discussion if they want to display warnings AND evaluate the code.