Symptom:

• MethodAccessorImpl NoClassDefError happens with Scala.js 1.0.0-RC2, when compiling multiple Scala.JS projects. We have no such issue with Scala.js 0.6.x
• After rerunning fastOptJS, the compilation eventually succeeds.
• I'm using sbt 1.3.6 and JDK11. The same error happens with JDK8.

• CI log: https://github.com/wvlet/airframe/runs/385008133

It might be an issue of sbt-scalajs plugin and sbt-1.3.x's new classloader. (The same problem happens with sbt 1.2.8) I'll work on reproduction of this issue.

It seems the reflection call of PathOutputFile in the LinkerImpl is failing:

    private val outputFileMethod =
      loadMethod("PathOutputFile", "atomic", classOf[LinkerOutput.File], classOf[Path])

This is used here:

            val out = LinkerOutput(linkerImpl.outputFile(output.toPath))
              .withSourceMap(linkerImpl.outputFile(sourceMapFile.toPath)) <--------
              .withSourceMapURI(relURI(sourceMapFile.getName))
              .withJSFileURI(relURI(output.getName))

A workaround is splitting an aggregated project into a smaller set of projects and running fastOptJS individually.