Ignore empty directory layout in external classes dir

backend/src/main/scala/bloop/BloopClassFileManager.scala

@@ -217,14 +217,19 @@ final class BloopClassFileManager(
             clientExternalClassesDir: AbsolutePath,
             clientReporter: Reporter,
             clientTracer: BraveTracer
-        ) => {
-          clientTracer.traceTask("populate external classes dir as it's empty") { _ =>
-            Task {
-              if (!BloopPaths.isDirectoryEmpty(clientExternalClassesDir)) Task.unit
-              else {
-                if (BloopPaths.isDirectoryEmpty(outPaths.internalReadOnlyClassesDir)) {
-                  Task.unit
-                } else {
+        ) =>
+          Task.defer {
+            // Exclude dirs because process controlling external dir might have created empty dir layouts
+            val externalDirHasFiles =
+              !BloopPaths.isDirectoryEmpty(clientExternalClassesDir, excludeDirs = true)
+            val isInternalEmpty =
+              BloopPaths.isDirectoryEmpty(outPaths.internalReadOnlyClassesDir, excludeDirs = false)
+
+            if (externalDirHasFiles) Task.unit
+            else if (isInternalEmpty) Task.unit
+            else
+              clientTracer.traceTask("populate empty classes dir") {
+                _ =>
                   // Prepopulate external classes dir even though compilation failed
                   val config = ParallelOps.CopyConfiguration(1, CopyMode.NoReplace, Set.empty)
                   ParallelOps
@@ -236,11 +241,8 @@ final class BloopClassFileManager(
                       enableCancellation = false
                     )
                     .map(_ => ())
-                }
               }
-            }.flatten
           }
-        }
       )
     }
   }

config/.jvm/src/test/scala/bloop/config/TestPlatform.scala

@@ -1,6 +1,21 @@
 package bloop.config
 
+import java.io.InputStreamReader
+import java.io.BufferedReader
+import java.util.stream.Collectors
+
 object TestPlatform {
-  def getResourceAsString(resource: String): String =
-    getClass.getClassLoader.getResourceAsStream(resource).readAllBytes().map(_.toChar).mkString
+  def getResourceAsString(resource: String): String = {
+    val stream = getClass.getClassLoader.getResourceAsStream(resource)
+    if (stream == null) sys.error(s"Missing resource $resource!")
+    else {
+      try {
+        val isr = new InputStreamReader(stream)
+        try {
+          val reader = new BufferedReader(isr)
+          reader.lines().collect(Collectors.joining(System.lineSeparator))
+        } finally (isr.close())
+      } finally stream.close()
+    }
+  }
 }

shared/src/main/scala/bloop/io/Paths.scala

@@ -171,7 +171,7 @@ object Paths {
     ()
   }
 
-  def isDirectoryEmpty(path: AbsolutePath): Boolean = {
+  def isDirectoryEmpty(path: AbsolutePath, excludeDirs: Boolean): Boolean = {
     var isEmpty: Boolean = true
     import java.nio.file.NoSuchFileException
     try {
@@ -187,7 +187,7 @@ object Paths {
               directory: Path,
               attributes: BasicFileAttributes
           ): FileVisitResult = {
-            if (path.underlying == directory) FileVisitResult.CONTINUE
+            if (excludeDirs || path.underlying == directory) FileVisitResult.CONTINUE
             else {
               isEmpty = false
               FileVisitResult.TERMINATE