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Update scalacOptions for Scala 3.8 #860

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Update scalacOptions for Scala 3.8 #860

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17 changes: 16 additions & 1 deletion settings/src/main/scala/org/typelevel/sbt/TypelevelSettingsPlugin.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -279,6 +279,8 @@ object TypelevelSettingsPlugin extends AutoPlugin {
)
}

val log = streams.value.log

scalaVersion.value match {
case V(V(2, 11, _, _)) =>
oldTargetOption
Expand All @@ -296,7 +298,20 @@ object TypelevelSettingsPlugin extends AutoPlugin {
releaseOption

case V(V(3, minor, _, _)) if minor >= 2 =>
javaOutputVersionOption
if (minor <= 7) {
javaOutputVersionOption
} else {
// https://www.scala-lang.org/news/next-scala-lts-jdk.html
tlJdkRelease.value match {
case Some(n) if n >= 17 =>
javaOutputVersionOption
case Some(n) =>
log.warn(s"tlJdkRelease is ${n} but scala ${scalaVersion.value} require JDK 17")
Seq.empty
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@armanbilge armanbilge Feb 9, 2026

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Suggested change
Seq.empty
Seq("-java-output-version", 17)

I think returning Seq.empty here is the wrong behavior. Instead, we should bump the JDK release to 17.

To explain why: developers specify this flag so that the compiler prevents them from using JDK APIs that are too new. For example, APIs introduced in Java 21. Even if a JDK release version of 8 or 11 is no longer compatible with Scala 3.8+, we should still ensure that the compiler will prevent the use of APIs from JDKs >17.

In fact, I would even say the warning would just be noise and we can make this adjustment silently. By choosing to use Scala 3.8+, the developer is already opting-in to minimum JDK 17+.

case None =>
Seq.empty
}
}

case _ =>
Seq.empty
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