Fix completely broken lock during setuping local repo on Linux (#3846)

* Fix completely broken lock during setuping local repo on Linux

On Solaris/Linux if DELETE_ON_CLOSE is specified, the appropriate file is
unlinked from the directory when opened and therefore appears inaccessible via
path. In this case, each Scala-CLI process considers itself holding the lock,
leading to a race condition.

Ref: https://bugs.openjdk.org/browse/JDK-7095452

Signed-off-by: unlsycn <unlsycn@unlsycn.com>

* Add test for parallel local repo setup

Signed-off-by: unlsycn <unlsycn@unlsycn.com>

---------

Signed-off-by: unlsycn <unlsycn@unlsycn.com>

Author: unlsycn

modules/build/src/main/scala/scala/build/LocalRepo.scala

@@ -77,11 +77,7 @@ object LocalRepo {
           // potential race conditions between initial check and lock acquisition
           if !os.exists(repoDir) then
             val tmpRepoDir = repoDir / os.up / s".$version.tmp"
-            try os.remove.all(tmpRepoDir)
-            catch {
-              case t: Throwable =>
-                logger.message(s"Error removing $tmpRepoDir: ${t.getMessage}")
-            }
+            os.remove.all(tmpRepoDir)
             using(archiveUrl.openStream()) { is =>
               using(WrappedZipInputStream.create(new BufferedInputStream(is))) { zis =>
                 extractZip(zis, tmpRepoDir)
@@ -101,30 +97,21 @@ object LocalRepo {
       val lockFile = dir.resolve(s".lock-$id");
       Util.createDirectories(lockFile.getParent)
       var channel: FileChannel = null
+      var lock: FileLock       = null
 
       try {
         channel = FileChannel.open(
           lockFile,
           StandardOpenOption.CREATE,
-          StandardOpenOption.WRITE,
-          StandardOpenOption.DELETE_ON_CLOSE
+          StandardOpenOption.WRITE
         )
-
-        var lock: FileLock = null
-        try {
-          lock = channel.lock()
-
-          try f
-          finally {
-            lock.release()
-            lock = null
-            channel.close()
-            channel = null
-          }
-        }
-        finally if (lock != null) lock.release()
+        lock = channel.lock()
+        f
+      }
+      finally {
+        if (lock != null) lock.release()
+        if (channel != null) channel.close()
       }
-      finally if (channel != null) channel.close()
     }
 
 }

modules/integration/src/test/scala/scala/cli/integration/RunTestDefinitions.scala

@@ -2413,4 +2413,29 @@ abstract class RunTestDefinitions
         expect(!res.err.trim().contains(legacyRunnerWarning))
       }
   }
+
+  for (parallelInstancesCount <- Seq(2, 5, 10))
+    test(
+      s"run $parallelInstancesCount instances in parallel without local repo"
+    ) {
+      TestInputs.empty.fromRoot { root =>
+        val localRepoPath =
+          os.Path(os.proc(
+            TestUtil.cli,
+            "directories",
+            "--power"
+          ).call().out.text().linesIterator.find(_.startsWith("Local repository:")).getOrElse(
+            throw new RuntimeException("Local repository line not found in directories output")
+          ).split(":", 2).last.trim())
+        os.remove.all(localRepoPath)
+
+        val processes =
+          (0 until parallelInstancesCount).map { _ =>
+            os.proc(TestUtil.cli, "--version")
+              .spawn(cwd = root)
+          }.zipWithIndex
+        processes.foreach { case (p, _) => p.waitFor() }
+        processes.foreach { case (p, _) => expect(p.exitCode == 0) }
+      }
+    }
 }