Add Scala 2.13.0-M4 support

please 😺

ref typelevel/cats#2267

[xuwei-k]

prepare Scala 2.13.0-M4 #224
(scala-js 0.6.22 does not support Scala 2.13.0-M4)

[xuwei-k]

scalac-scoverage-plugin depends on scala-logging (only test) lightbend-labs/scala-logging#127

[SethTisue]

scala-logging 3.9.0 has now been published for M4

[gslowikowski]

There is a problem with this version. Guys, I need you help.

Here are the branches:
https://github.com/scoverage/scalac-scoverage-plugin/tree/scala-2-13-0-M4
https://github.com/scoverage/sbt-scoverage/tree/scala-2-13-0-M4

Please, publish the plugin locally and try to build any project with sbt clean coverage compile
While compiling I have:

...
[info] [info] Beginning coverage instrumentation
[info] [info] Instrumentation completed [9 statements]
[error] ## Exception when compiling 1 sources to ${path\to\my\project}\target\scala-2.13.0-M4\classes
[error] scala/xml/NamespaceBinding
[error] scoverage.ScoverageInstrumentationComponent$$anon$1.run(plugin.scala:125)
[error] scala.tools.nsc.Global$Run.compileUnitsInternal(Global.scala:1449)
[error] scala.tools.nsc.Global$Run.compileUnits(Global.scala:1433)
[error] scala.tools.nsc.Global$Run.compileSources(Global.scala:1425)
[error] scala.tools.nsc.Global$Run.compile(Global.scala:1542)
[error] xsbt.CachedCompiler0.run(CompilerInterface.scala:130)
[error] xsbt.CachedCompiler0.run(CompilerInterface.scala:105)
[error] xsbt.CompilerInterface.run(CompilerInterface.scala:31)
[error] sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] java.lang.reflect.Method.invoke(Method.java:498)
[error] sbt.internal.inc.AnalyzingCompiler.call(AnalyzingCompiler.scala:237)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:111)
[error] sbt.internal.inc.AnalyzingCompiler.compile(AnalyzingCompiler.scala:90)
[error] sbt.internal.inc.MixedAnalyzingCompiler.$anonfun$compile$3(MixedAnalyzingCompiler.scala:83)
[error] scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
[error] sbt.internal.inc.MixedAnalyzingCompiler.timed(MixedAnalyzingCompiler.scala:134)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compileScala$1(MixedAnalyzingCompiler.scala:74)
[error] sbt.internal.inc.MixedAnalyzingCompiler.compile(MixedAnalyzingCompiler.scala:117)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1(IncrementalCompilerImpl.scala:305)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileInternal$1$adapted(IncrementalCompilerImpl.scala:305)
[error] sbt.internal.inc.Incremental$.doCompile(Incremental.scala:101)
[error] sbt.internal.inc.Incremental$.$anonfun$compile$4(Incremental.scala:82)
[error] sbt.internal.inc.IncrementalCommon.recompileClasses(IncrementalCommon.scala:110)
[error] sbt.internal.inc.IncrementalCommon.cycle(IncrementalCommon.scala:57)
[error] sbt.internal.inc.Incremental$.$anonfun$compile$3(Incremental.scala:84)
[error] sbt.internal.inc.Incremental$.manageClassfiles(Incremental.scala:129)
[error] sbt.internal.inc.Incremental$.compile(Incremental.scala:75)
[error] sbt.internal.inc.IncrementalCompile$.apply(Compile.scala:61)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileInternal(IncrementalCompilerImpl.scala:309)
[error] sbt.internal.inc.IncrementalCompilerImpl.$anonfun$compileIncrementally$1(IncrementalCompilerImpl.scala:267)
[error] sbt.internal.inc.IncrementalCompilerImpl.handleCompilationError(IncrementalCompilerImpl.scala:158)
[error] sbt.internal.inc.IncrementalCompilerImpl.compileIncrementally(IncrementalCompilerImpl.scala:237)
[error] sbt.internal.inc.IncrementalCompilerImpl.compile(IncrementalCompilerImpl.scala:68)
[error] sbt.Defaults$.compileIncrementalTaskImpl(Defaults.scala:1427)
[error] sbt.Defaults$.$anonfun$compileIncrementalTask$1(Defaults.scala:1401)
[error] scala.Function1.$anonfun$compose$1(Function1.scala:44)
[error] sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:39)
[error] sbt.std.Transform$$anon$4.work(System.scala:66)
[error] sbt.Execute.$anonfun$submit$2(Execute.scala:262)
[error] sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:16)
[error] sbt.Execute.work(Execute.scala:271)
[error] sbt.Execute.$anonfun$submit$1(Execute.scala:262)
[error] sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:174)
[error] sbt.CompletionService$$anon$2.call(CompletionService.scala:36)
[error] java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[error] java.util.concurrent.FutureTask.run(FutureTask.java:266)
[error] java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[error] java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[error] java.lang.Thread.run(Thread.java:748)
[error]
[error] java.lang.NoClassDefFoundError: scala/xml/NamespaceBinding
[error]         at scoverage.ScoverageInstrumentationComponent$$anon$1.run(plugin.scala:125)
[error]         at scala.tools.nsc.Global$Run.compileUnitsInternal(Global.scala:1449)
...

[SethTisue]

looks like you're doing XML stuff but don't have scala-xml on the classpath. as of 2.13.0-M4, scala-compiler no longer depends on scala-xml, that seems like a likely root cause

idk, but perhaps this line of code needs updating? val scalaJars = List("scala-compiler", "scala-library", "scala-reflect")

[gslowikowski]

I have scala-xml dependency, here. It was always there, only the version changes.

For me it looks like something has changed with plugin's classloader/classpath.

[SethTisue]

I don't know of any Scala change that might cause that, other than the one I mentioned. Perhaps there is an implicit assumption in your code that loading the scala-compiler classes also causes the scala-xml classes to be loaded in the same classloader.

[gslowikowski]

I found it, scala-compiler does not depend on scala-xml anymore (since this commit).

Project's dependency on scala-xml is not used in scalac compilation context, but Scala compiler provided it anyway up to version 2.13.0-M3.

[JanBessai]

Tests in the 2.13.0-M4 tree seem to work fine, except for the yielder. Adding some embarrassing printf-debugging code, I was able to obtain a direct comparison. You can see that the new collections API eliminates two calls to canBuildFrom(), which were counted previously (but not mentioned in the test comment).
I guess you can fix this in two ways: the hard way would be a split of the test-base and the easy way would be to expect two statements less.
Also, the explanation for the test seems to be a little misleading, since it counts canBuildFrom as map and flatMap.

[SethTisue]

the hard way would be a split of the test-base

(maybe not so hard — I'm not sure how widely known it is that you can have src/test/scala-2.11, src/test/scala-2.12 and so forth and sbt will pick up the version-specific sources automatically. see my comment at twitter/util#219 (comment))

[JanBessai]

Now pull-request #228 tests fine in Travis. Splitting the test-base as suggested by @SethTisue would be an alternative, but perhaps it is a bit much for a problem validly solvable with a simple weakening of a single == to <=.
Maybe the split could become a long-term todo, if more need for it arises. For now it would be great to have a working pre-release compatible with Scala 2.13.0-M4.

[gslowikowski]

@JanBessai's changes are merged to master.

Now we come to the point I've described above

How to solve it? Scoverage needs scala-xml, but scalac plugins cannot have dependencies in the context of compilation.