Issue1675

When executing a Python file with the command line:

jython program.py

The Jython interpreter exits immediately with System.exit() upon finishing executing the script.
The result is that any Swing windows that are open are closed immediately, upon Jython reaching the end of the program (instead of waiting for the user to close them) - Swing applications cannot run normally.

At the end of jython#run()  (org.jython.util package)
are the lines:

        interp.cleanup();
        if (opts.fixInteractive || opts.interactive) {
            System.exit(0);
        }


It seems that when running a file, opts.interactive has a value of true.

Could you please show the script you tried to run?

Nevermind, I tested with the binding example of jython-swingutils and it does not run either. This is borked.

opts.interactive means, does the process that runs this code a console (a tty), irrespective if it's a script or not? In the past, we didn't correctly perform this a test. The main fix for RC2 was to correct this, so it would work with ipython. Naturally it's causing issues on code that relied on this broken functionality, as seen here at the end of #run.

We need some sort of fix for RC3.

After many hours of testing, i came to the conclusion that this is NOT reproducible with Runtime.exec() (or it's higher level abstractions Popen and subprocess). 
The reason is that java's Runtime.exec() always waits until the last Thread has finished, regardles of the System.exit() in the jython run method.

The obvious workaround is to start jython with the -i flag

The following code reproduces it:

from javax.swing import *

label = JLabel( 'Hello world' )
frame = JFrame()
frame.add( label )
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE )

frame.show()


Also attached as a file.

Running it with 'jython swingtest.py' exits immediately, closing the window, instead of waiting for the user to close it.
Running it with 'jython -i swingtest.py' does not, but requires that Jython is closed manually from the jython prompt.


Commenting out the 'System.exit(0);' line in jython.java allows the program to run with 'jython swingtest.py' as one would expect it to.



My platform:

Windows Vista 64

java version "1.6.0_22"
Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
Java HotSpot(TM) Client VM (build 17.1-b03, mixed mode, sharing)

Jython: r7171

Geoffrey,
sorry for the confusion. Of course it is reproducible from the command line. What I meant is that it is very hard to reproduce in a unit test by calling the jython command from java.

Here's a work-around that can be put at the end of a program's main application code:

    # work around Jython bug that kills Swing thread on main exit
    import threading
    while True:
        alive = False
        for thread in threading.enumerate():
            if not thread.isDaemon():
                alive = True
                thread.join(2)
        if not alive:
            sys.exit(0)

Attached a patch with a potential fix. This passes the regrtest. Might this break anything else?

looking at r7161 (the orig IPython fix), it's doubtful that this patch would hurt IPython. Can someone try it with IPython or describe the IPython broken behavior prior to r7161?

The patched ipython seems ok AFAICT with this patch. this doesn't touch the interactivity flag at all anyway, so we should be good. applied in r7177