FULL PRODUCT VERSION :
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
I'm using jdk.nashorn.api.scripting.URLReader with Nashorn script engine to evaluate a script from a file (passing the file URL to the reader). After the evaluation is finished (and the reader closed explicitly) often the script file stays locked.

I have attached a test program to reproduce the bug, which creates a test script file, evaluates it and attempts to delete it after that. The deletion fails quite often (i.e. on the third/fourth test), but not always, which makes me believe a synchronization issue is at hand.

The attached program runs 10 such tests and reliably fails on every run.

Note that if the reader at line 33:

Reader reader = new URLReader(scriptURL);

is replaced with

Reader reader = new InputStreamReader(scriptURL.openStream());

the program finishes without error.


REPRODUCIBILITY :
This bug can be reproduced often.

---------- BEGIN SOURCE ----------
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.Reader;
import java.net.URL;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

import jdk.nashorn.api.scripting.URLReader;

public class Main {

  private static final File SCRIPT_FILE = new File("test.js");
  private static final String SCRIPT = "print('test')";

  public static void main(String[] args) throws Exception {
    for (int i = 0; i < 10; i++) {
      test();
    }

    System.out.println("All swell");
  }

  public static void test() throws Exception {
    saveFile(SCRIPT_FILE, SCRIPT);

    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByExtension("js");

    URL scriptURL = SCRIPT_FILE.toURI().toURL();
    Reader reader = new URLReader(scriptURL);
    try {
      engine.eval(reader);
    } catch (ScriptException ex) {
      System.err.println(ex.getMessage());
    } finally {
      reader.close();
    }

    boolean deleted = SCRIPT_FILE.delete();

    if (!deleted) {
      throw new Exception("Failed to delete script file");
    }
  }

  private static void saveFile(File file, String contents) throws IOException {
    FileOutputStream out = new FileOutputStream(file);

    try {
      out.write(contents.getBytes());
    } finally {
      out.close();
    }
  }

}
---------- END SOURCE ----------