I have a Scala project that can only be compiled with Gradle, recently someone has asked it to be ported to Scala.js, ideally by cross-build.
When I read the code of Scala.js, I realised that the bulk of the plugin is actually a compiler (scalac) plugin:
import scala.tools.nsc.plugins.{
Plugin => NscPlugin, PluginComponent => NscPluginComponent
}
...
class ScalaJSPlugin(val global: Global) extends NscPlugin {
import global._
...
But all the documentations have suggested to use it as part of the sbt-plugin, which are useless in my case. So I try to attach it to my scalac process, invoked through gradle:
dependencies {
implementation("org.scala-js:scalajs-library_${vs.scalaBinaryV}:${vs.scalaJSV}")
scalaCompilerPlugins("org.scala-js:scalajs-compiler_${vs.scalaV}:${vs.scalaJSV}")
...
This experiment unfortunately doesn't work. The compiler threw the following error:
> Task :compileTestFixturesScala FAILED
## Exception when compiling 1 sources to /home/peng/git-scaffold/scaffold-gradle-kts/build/classes/scala/testFixtures
scala.reflect.internal.MissingRequirementError: object scala.scalajs.js.Dynamic in compiler mirror not found.
scala.reflect.internal.MissingRequirementError$.notFound(MissingRequirementError.scala:24)
scala.reflect.internal.Mirrors$RootsBase.$anonfun$getModuleOrClass$6(Mirrors.scala:66)
scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:66)
scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:56)
scala.reflect.internal.Mirrors$RootsBase.getRequiredClass(Mirrors.scala:56)
org.scalajs.nscplugin.JSDefinitions$JSDefinitionsClass.JSDynamicClass$lzycompute(JSDefinitions.scala:52)
org.scalajs.nscplugin.JSDefinitions$JSDefinitionsClass.JSDynamicClass(JSDefinitions.scala:52)
org.scalajs.nscplugin.JSDefinitions$JSDefinitionsClass.JSDynamicModule$lzycompute(JSDefinitions.scala:83)
org.scalajs.nscplugin.JSDefinitions$JSDefinitionsClass.JSDynamicModule(JSDefinitions.scala:83)
org.scalajs.nscplugin.JSDefinitions$JSDefinitionsClass.JSDynamic_newInstance$lzycompute(JSDefinitions.scala:84)
org.scalajs.nscplugin.JSDefinitions$JSDefinitionsClass.JSDynamic_newInstance(JSDefinitions.scala:84)
org.scalajs.nscplugin.JSPrimitives.initWithPrimitives(JSPrimitives.scala:89)
org.scalajs.nscplugin.JSPrimitives.initPrepJSPrimitives(JSPrimitives.scala:77)
org.scalajs.nscplugin.PrepJSInterop$JSInteropPhase.run(PrepJSInterop.scala:65)
scala.tools.nsc.Global$Run.compileUnitsInternal(Global.scala:1524)
scala.tools.nsc.Global$Run.compileUnits(Global.scala:1508)
scala.tools.nsc.Global$Run.compileSources(Global.scala:1500)
scala.tools.nsc.Global$Run.compile(Global.scala:1634)
xsbt.CachedCompiler0.run(CompilerInterface.scala:153)
xsbt.CachedCompiler0.run(CompilerInterface.scala:125)
xsbt.CompilerInterface.run(CompilerInterface.scala:39)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:498)
sbt.internal.inc.AnalyzingCompiler.call(AnalyzingCompiler.scala:248)
sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:122)
sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:95)
sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$4(MixedAnalyzingCompiler.scala:91)
scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:186)
sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3(MixedAnalyzingCompiler.scala:82)
sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3$adapted(MixedAnalyzingCompiler.scala:77)
sbt.internal.inc.JarUtils$.withPreviousJar(JarUtils.scala:215)
sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:77)
sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:146)
sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:343)
sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:343)
sbt.internal.inc.Incremental$.doCompile(Incremental.scala:120)
sbt.internal.inc.Incremental$.$anonfun$compile$4(Incremental.scala:100)
sbt.internal.inc.IncrementalCommon.recompileClasses(IncrementalCommon.scala:180)
sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:98)
sbt.internal.inc.Incremental$.$anonfun$compile$3(Incremental.scala:102)
sbt.internal.inc.Incremental$.manageClassfiles(Incremental.scala:155)
sbt.internal.inc.Incremental$.compile(Incremental.scala:92)
sbt.internal.inc.IncrementalCompile$.apply(Compile.scala:75)
sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:348)
sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:301)
sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:168)
sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:248)
sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:74)
org.gradle.api.internal.tasks.scala.ZincScalaCompiler.execute(ZincScalaCompiler.java:157)
org.gradle.api.internal.tasks.scala.ZincScalaCompilerFacade.execute(ZincScalaCompilerFacade.java:47)
org.gradle.api.internal.tasks.scala.ZincScalaCompilerFacade.execute(ZincScalaCompilerFacade.java:32)
org.gradle.api.internal.tasks.compile.daemon.AbstractDaemonCompiler$CompilerWorkAction.execute(AbstractDaemonCompiler.java:135)
org.gradle.workers.internal.DefaultWorkerServer.execute(DefaultWorkerServer.java:63)
org.gradle.workers.internal.AbstractClassLoaderWorker$1.create(AbstractClassLoaderWorker.java:49)
org.gradle.workers.internal.AbstractClassLoaderWorker$1.create(AbstractClassLoaderWorker.java:43)
org.gradle.internal.classloader.ClassLoaderUtils.executeInClassloader(ClassLoaderUtils.java:97)
org.gradle.workers.internal.AbstractClassLoaderWorker.executeInClassLoader(AbstractClassLoaderWorker.java:43)
org.gradle.workers.internal.IsolatedClassloaderWorker.run(IsolatedClassloaderWorker.java:49)
org.gradle.workers.internal.IsolatedClassloaderWorker.run(IsolatedClassloaderWorker.java:30)
org.gradle.workers.internal.WorkerDaemonServer.run(WorkerDaemonServer.java:87)
org.gradle.workers.internal.WorkerDaemonServer.run(WorkerDaemonServer.java:56)
org.gradle.process.internal.worker.request.WorkerAction$1.call(WorkerAction.java:138)
org.gradle.process.internal.worker.child.WorkerLogEventListener.withWorkerLoggingProtocol(WorkerLogEventListener.java:41)
org.gradle.process.internal.worker.request.WorkerAction.run(WorkerAction.java:135)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:498)
org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:182)
org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:164)
org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:414)
org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64)
org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)
Despite that, this error seems to be caused by trivial missing class, and it happens at a fairly late stage of compilation, when test code are being compiled.
So my question is: what does it take to make scalajs to work as a compiler plugin (WITHOUT sbt)? And what could possibly cause this error?
That error is typically symptomatic of not having scalajs-library on the compilation classpath. But I see you already added
implementation("org.scala-js:scalajs-library_${vs.scalaBinaryV}:${vs.scalaJSV}")
which, from what I understand of Gradle, should do that.
Perhaps double-check that that library indeed ends up on the compilation classpath, using whatever command Gradle offers to check that?
That said, after you're done with this, all you'll have are .sjsir files, which cannot be run or tested. You will need the Scala.js linker to process the .sjsir files on the classpath, and produce one .js file.