From a946cbf702d2d7fa2a0496932768963c9c2be686 Mon Sep 17 00:00:00 2001
From: Ethan Atkins <contact@ethanatkins.com>
Date: Tue, 15 Sep 2020 08:27:12 -0700
Subject: [PATCH] Skip contents of symlinked directories in clean

The clean task was previously deleting the contents of directories that
were symlinked into the target directory. This was an oversight because
it never occurred to me that users might symlink a directory whose
contents they did not want deleted into the target directory.
---
 main/src/main/scala/sbt/internal/Clean.scala  | 14 +++++---------
 sbt/src/sbt-test/nio/clean-symlinks/build.sbt |  5 +++++
 sbt/src/sbt-test/nio/clean-symlinks/foo/bar   |  1 +
 sbt/src/sbt-test/nio/clean-symlinks/test      |  9 +++++++++
 4 files changed, 20 insertions(+), 9 deletions(-)
 create mode 100644 sbt/src/sbt-test/nio/clean-symlinks/build.sbt
 create mode 100644 sbt/src/sbt-test/nio/clean-symlinks/foo/bar
 create mode 100644 sbt/src/sbt-test/nio/clean-symlinks/test

diff --git a/main/src/main/scala/sbt/internal/Clean.scala b/main/src/main/scala/sbt/internal/Clean.scala
index a5b19e465..0f314fd60 100644
--- a/main/src/main/scala/sbt/internal/Clean.scala
+++ b/main/src/main/scala/sbt/internal/Clean.scala
@@ -41,7 +41,7 @@ private[sbt] object Clean {
         .list(Glob(path, AnyPath))
         .filterNot { case (p, _) => exclude(p) }
         .foreach {
-          case (dir, attrs) if attrs.isDirectory =>
+          case (dir, attrs) if attrs.isDirectory && !attrs.isSymbolicLink =>
             deleteRecursive(dir)
             delete(dir)
           case (file, _) => delete(file)
@@ -89,15 +89,11 @@ private[sbt] object Clean {
         val excludeFilter = cleanFilter(scope).value
         val delete = cleanDelete(scope).value
         val targetDir = (target in scope).?.value.map(_.toPath)
-        def recursiveFiles(dir: Path): Seq[Path] =
-          view.list(dir.toGlob / **).collect { case (p, _) if !excludeFilter(p) => p }
-        val targetFiles = (if (full) targetDir else None).fold(Nil: Seq[Path])(recursiveFiles)
-        val cleanPaths = (cleanFiles in scope).?.value.getOrElse(Nil).flatMap { f =>
-          val path = f.toPath
-          if (Files.isDirectory(path)) path +: recursiveFiles(path) else path :: Nil
+
+        targetDir.filter(_ => full).foreach(deleteContents(_, excludeFilter, view, delete))
+        (cleanFiles in scope).?.value.getOrElse(Nil).foreach { f =>
+          deleteContents(f.toPath, excludeFilter, view, delete)
         }
-        val allFiles = cleanPaths.view ++ targetFiles
-        allFiles.sorted.reverseIterator.foreach(delete)
 
         // This is the special portion of the task where we clear out the relevant streams
         // and file outputs of a task.
diff --git a/sbt/src/sbt-test/nio/clean-symlinks/build.sbt b/sbt/src/sbt-test/nio/clean-symlinks/build.sbt
new file mode 100644
index 000000000..b7ad34a81
--- /dev/null
+++ b/sbt/src/sbt-test/nio/clean-symlinks/build.sbt
@@ -0,0 +1,5 @@
+import java.nio.file.Files
+
+TaskKey[Unit]("createSymlinkedDirectory") := {
+  Files.createSymbolicLink(target.value.toPath / "foo", baseDirectory.value.toPath / "foo")
+}
diff --git a/sbt/src/sbt-test/nio/clean-symlinks/foo/bar b/sbt/src/sbt-test/nio/clean-symlinks/foo/bar
new file mode 100644
index 000000000..5716ca598
--- /dev/null
+++ b/sbt/src/sbt-test/nio/clean-symlinks/foo/bar
@@ -0,0 +1 @@
+bar
diff --git a/sbt/src/sbt-test/nio/clean-symlinks/test b/sbt/src/sbt-test/nio/clean-symlinks/test
new file mode 100644
index 000000000..48dfcb255
--- /dev/null
+++ b/sbt/src/sbt-test/nio/clean-symlinks/test
@@ -0,0 +1,9 @@
+> createSymlinkedDirectory
+
+$ exists target/foo/bar
+$ exists foo/bar
+
+> clean
+
+$ absent target/foo
+$ exists foo/bar