Flakiness in scalalib example tests

[lihaoyi]

example.scalalib.web[7-cross-version-platform-publishing].native.server.test and 8-cross-platform-version-publishing seem to flake a lot since the Scala 3 upgrade. Seems to be something to do with .docJar failing?

Example failure

https://github.com/alexarchambault/mill/actions/runs/13291005727/job/37112051566

[6764]   utest.AssertionError: evalResult.isSuccess
[6764]   evalResult: mill.testkit.IntegrationTester.EvalResult = EvalResult(false,[info] compiling 2 Scala sources to /home/runner/work/mill/mill/out/example/scalalib/web/7-cross-version-platform-publishing/native/server/test.dest/sandbox/run-2/out/foo/3.3.3/bar/jvm/compile.dest/classes ...
[6764]   [info] compiling 2 Scala sources to /home/runner/work/mill/mill/out/example/scalalib/web/7-cross-version-platform-publishing/native/server/test.dest/sandbox/run-2/out/foo/2.13.14/bar/js/compile.dest/classes ...
[6764]   Publishing Artifact(com.lihaoyi,foo-bar_2.13,0.0.1) to ivy repo /home/runner/.ivy2/local
[6764]   Publishing Artifact(com.lihaoyi,foo-bar_sjs1_3,0.0.1) to ivy repo /home/runner/.ivy2/local
[6764]   Publishing Artifact(com.lihaoyi,foo-qux_2.13,0.0.1) to ivy repo /home/runner/.ivy2/local
[6764]   Publishing Artifact(com.lihaoyi,foo-qux_sjs1_3,0.0.1) to ivy repo /home/runner/.ivy2/local
[6764]   [info] done compiling
[6764]   [info] compiling 2 Scala sources to /home/runner/work/mill/mill/out/example/scalalib/web/7-cross-version-platform-publishing/native/server/test.dest/sandbox/run-2/out/foo/2.13.14/qux/js/compile.dest/classes ...
[6764]   [info] done compiling
[6764]   [info] compiling 2 Scala sources to /home/runner/work/mill/mill/out/example/scalalib/web/7-cross-version-platform-publishing/native/server/test.dest/sandbox/run-2/out/foo/3.3.3/qux/jvm/compile.dest/classes ...
[6764]   [info] done compiling
[6764]   Publishing Artifact(com.lihaoyi,foo-bar_sjs1_2.13,0.0.1) to ivy repo /home/runner/.ivy2/local
[6764]   Publishing Artifact(com.lihaoyi,foo-bar_3,0.0.1) to ivy repo /home/runner/.ivy2/local
[6764]   [info] done compiling
[6764]   1 tasks failed
[6764]   foo[2.13.14].qux.js.docJar java.lang.reflect.InvocationTargetException
[6764]       java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[6764]       java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[6764]       java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[6764]       java.base/java.lang.reflect.Method.invoke(Method.java:566)
[6764]       mill.scalalib.worker.ZincWorkerImpl.docJar$$anonfun$1(ZincWorkerImpl.scala:258)
[6764]       mill.scalalib.worker.ZincWorkerImpl.withCompilers$$anonfun$1(ZincWorkerImpl.scala:489)
[6764]       mill.util.CachedFactory.withValue(CachedFactory.scala:39)
[6764]       mill.scalalib.worker.ZincWorkerImpl.withCompilers(ZincWorkerImpl.scala:488)
[6764]       mill.scalalib.worker.ZincWorkerImpl.docJar(ZincWorkerImpl.scala:230)
[6764]       mill.scalalib.ScalaModule.packageWithZinc$1(ScalaModule.scala:317)
[6764]       mill.scalalib.ScalaModule.docJar$$anonfun$1$$anonfun$1(ScalaModule.scala:416)
[6764]       mill.define.Task$TraverseCtx.evaluate(Task.scala:231)
[6764]   java.io.IOException: Stream closed
[6764]       java.base/java.util.zip.InflaterInputStream.ensureOpen(InflaterInputStream.java:68)
[6764]       java.base/java.util.zip.InflaterInputStream.read(InflaterInputStream.java:143)
[6764]       java.base/java.io.FilterInputStream.read(FilterInputStream.java:133)
[6764]       java.base/java.io.BufferedInputStream.fill(BufferedInputStream.java:252)
[6764]       java.base/java.io.BufferedInputStream.read(BufferedInputStream.java:271)
[6764]       scala.reflect.io.Streamable$Bytes.$anonfun$bytesAsInts$1(Streamable.scala:48)
[6764]       scala.runtime.java8.JFunction0$mcI$sp.apply(JFunction0$mcI$sp.scala:17)
[6764]       scala.collection.Iterator$$anon$27.next(Iterator.scala:1135)
[6764]       scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:637)
[6764]       scala.collection.Iterator$$anon$9.hasNext(Iterator.scala:583)
[6764]       scala.collection.mutable.Growable.addAll(Growable.scala:61)
[6764]       scala.collection.mutable.Growable.addAll$(Growable.scala:57)
[6764]       scala.collection.mutable.ArrayBuffer.addAll(ArrayBuffer.scala:160)
[6764]       scala.collection.mutable.ArrayBuffer.addAll(ArrayBuffer.scala:42)
[6764]       scala.reflect.io.Streamable$Bytes.toByteArray(Streamable.scala:57)
[6764]       scala.reflect.io.Streamable$Bytes.toByteArray$(Streamable.scala:54)
[6764]       scala.tools.nsc.doc.html.HtmlFactory.copyResource$1(HtmlFactory.scala:108)
[6764]       scala.tools.nsc.doc.html.HtmlFactory.$anonfun$generate$1(HtmlFactory.scala:148)
[6764]       scala.tools.nsc.doc.html.HtmlFactory.generate(HtmlFactory.scala:148)
[6764]       scala.tools.nsc.doc.html.Doclet.generateImpl(Doclet.scala:30)
[6764]       scala.tools.nsc.doc.doclet.Generator.generate(Generator.scala:35)
[6764]       scala.tools.nsc.doc.DocFactory.generate$1(DocFactory.scala:139)
[6764]       scala.tools.nsc.doc.DocFactory.document(DocFactory.scala:142)
[6764]       scala.tools.nsc.ScalaDoc.process(ScalaDoc.scala:48)
[6764]       java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[6764]       java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[6764]       java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[6764]       java.base/java.lang.reflect.Method.invoke(Method.java:566)
[6764]       mill.scalalib.worker.ZincWorkerImpl.docJar$$anonfun$1(ZincWorkerImpl.scala:258)
[6764]       mill.scalalib.worker.ZincWorkerImpl.withCompilers$$anonfun$1(ZincWorkerImpl.scala:489)
[6764]       mill.util.CachedFactory.withValue(CachedFactory.scala:39)
[6764]       mill.scalalib.worker.ZincWorkerImpl.withCompilers(ZincWorkerImpl.scala:488)
[6764]       mill.scalalib.worker.ZincWorkerImpl.docJar(ZincWorkerImpl.scala:230)
[6764]       mill.scalalib.ScalaModule.packageWithZinc$1(ScalaModule.scala:317)
[6764]       mill.scalalib.ScalaModule.docJar$$anonfun$1$$anonfun$1(ScalaModule.scala:416)
[6764]       mill.define.Task$TraverseCtx.evaluate(Task.scala:231)
[6764]   ,)
[6764]     utest.asserts.Asserts$.assertImpl(Asserts.scala:30)
[6764]     mill.testkit.ExampleTester.validateEval(ExampleTester.scala:153)
[6764]     mill.testkit.ExampleTester.processCommand(ExampleTester.scala:142)
[6764]     mill.testkit.ExampleTester.processCommandBlock(ExampleTester.scala:96)
[6764]     mill.testkit.ExampleTester.run$$anonfun$1(ExampleTester.scala:205)
[6764]     scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
[6764]     scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
[6764]     scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
[6764]     mill.testkit.ExampleTester.run(ExampleTester.scala:205)
[6764]     mill.testkit.ExampleTester$.run(ExampleTester.scala:62)
[6764]     mill.testkit.UtestExampleTestSuite$.$init$$$anonfun$1$$anonfun$1$$anonfun$1(UtestExampleTestSuite.scala:20)
[6764]     mill.testkit.UtestExampleTestSuite$.$init$$$anonfun$1$$anonfun$1$$anonfun$adapted$1(UtestExampleTestSuite.scala:13)
[6764]     mill.util.Retry.apply$$anonfun$1(Retry.scala:32)
[6764]     mill.util.Retry.apply$$anonfun$adapted$1(Retry.scala:32)
[6764]     mill.util.Retry.$anonfun$1$$anonfun$1(Retry.scala:42)
[6764]     scala.util.Try$.apply(Try.scala:217)
[6764]     mill.util.Retry.$anonfun$1(Retry.scala:42)
[6764]     java.lang.Thread.run(Thread.java:829)
[6764] Tests: 1, Passed: 0, Failed: 1
[6764] [6764] example.scalalib.web[7-cross-version-platform-publishing].native.server.test failed

The stack trace points at this code in scala-compiler-2.13.15-sources.jar!/scala/tools/nsc/doc/html/HtmlFactory.scala

    def copyResource(subPath: String): Unit = {
      val bytes = new Streamable.Bytes {
        val p = "/scala/tools/nsc/doc/html/resource/" + subPath
        val inputStream = getClass.getResourceAsStream(p)
        assert(inputStream != null, p)
      }.toByteArray()
      val dest = Directory(siteRoot) / subPath
      dest.parent.createDirectory()
      val out = dest.toFile.bufferedOutput()
      try out.write(bytes, 0, bytes.length)
      finally out.close()
    }