UnsupportedClassVersionError since sbt-scalafmt 2.5.3

[xuwei-k]

Configuration (required)

use JDK 8

.scalafmt.conf

version = "3.8.3"
runner.dialect = Scala3

project/build.properties

sbt.version=1.10.7

project/plugins.sbt

addSbtPlugin("org.scalameta" % "sbt-scalafmt" % "2.5.3")

Command-line parameters (required)

sbt scalafmt

Problem (required)

java.lang.UnsupportedClassVersionError: org/scalafmt/interfaces/Scalafmt has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:757)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:473)
	at java.net.URLClassLoader.access$100(URLClassLoader.java:74)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:369)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:363)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:362)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:419)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:352)
	at org.scalafmt.sbt.ScalafmtPlugin$.<init>(ScalafmtPlugin.scala:108)
	at org.scalafmt.sbt.ScalafmtPlugin$.<clinit>(ScalafmtPlugin.scala)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:348)
	at sbt.internal.inc.ModuleUtilities$.getObject(ModuleUtilities.scala:24)
	at sbt.internal.inc.ModuleUtilities$.getCheckedObject(ModuleUtilities.scala:32)
	at sbt.internal.inc.ModuleUtilities$.$anonfun$getCheckedObjects$1(ModuleUtilities.scala:37)
	at scala.collection.immutable.Stream.map(Stream.scala:418)
	at sbt.internal.inc.ModuleUtilities$.getCheckedObjects(ModuleUtilities.scala:37)
	at sbt.internal.PluginDiscovery$.loadModules(PluginDiscovery.scala:164)

Expectation

Workaround

Notes

[kitbellew]

@tgodzik @xuwei-k @ckipp01 do you know how to solve this?

[kitbellew]

ok, chatgpt says 52.0 is for java 8, and 55.0 for java 11; it is true we no longer release for java 8. i thought java 8 was deprecated a while ago.

also, one of the contributors added a section mentioning that java 8 support was dropped in 2.5.1.

but in mima it used 2.5.2 successfully...

[gaeljw]

Facing the same error in cucumber/cucumber-jvm-scala#384, Java 8 support got dropped in 2.5.3 (was working in 2.5.2).

IMHO it should have been done in a minor version, not a bugfix one, with an explicit mention in the release notes even though we all agree that JDK8 should go away :)

[tgodzik]

@tgodzik @xuwei-k @ckipp01 do you know how to solve this?

We can separate release into website and normal release, which we can run on JDK 8 or just add -release 8 flag to scalacOptions. Both should work since mdoc documentation is not published. I can do that, just let me know.

We can drop the version explicitly later on.

[xuwei-k]

just add -release 8 flag to scalacOption

org/scalafmt/interfaces/Scalafmt is java code. not scalacOptions. add javacOptions

https://github.com/scalameta/scalafmt/blob/v3.8.4/scalafmt-interfaces/jvm/src/main/java/org/scalafmt/interfaces/Scalafmt.java

[tgodzik]

just add -release 8 flag to scalacOption

org/scalafmt/interfaces/Scalafmt is java code. not scalacOptions. add javacOptions

https://github.com/scalameta/scalafmt/blob/v3.8.4/scalafmt-interfaces/jvm/src/main/java/org/scalafmt/interfaces/Scalafmt.java

Ach, yes, sorry. We should most likely add both just in case

[kitbellew]

@tgodzik @xuwei-k @ckipp01 do you know how to solve this?

We can separate release into website and normal release, which we can run on JDK 8 or just add -release 8 flag to scalacOptions. Both should work since mdoc documentation is not published. I can do that, just let me know.

I tried adding scalacOptions ++= Seq("-release", "8") to -dynamic and -sysops, and also javacOptions ++= Seq("--release", "8") to -interfaces; then used javap -v on the resulting class files and saw 52 on the dynamic classes but 65 on the interfaces classes.

Whatever I did, I could't get java files to become 52. Since I don't know much about this, I used chatgpt and gemini to guide me, and they hallucinated a little bit but perhaps too much.

anyway, @tgodzik, if you understand how to do this, could you please help?

[tgodzik]

scalameta/scalafmt#4719

[xuwei-k]

thanks!