[JENKINS-59844] Process Launcher shouldn't throw ArrayIndexOutOfBoundException on empty command

[timja]

If you try to launch a blank command  ('  ') using Launch.ProcStarter#cmdAsSingleString, an ArrayIndexOutOfBoundException is thrown.

Example of command invocation:

launcher.launch()
    .cmdAsSingleString("   ")
    .envs(computer.getEnvironment())
    .readStdout()
    .pwd(rootPath)
    .start();

Exception thrown:

java.lang.ArrayIndexOutOfBoundsException: 0
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1014)
    at hudson.Proc$LocalProc.(Proc.java:249)
    at hudson.Proc$LocalProc.(Proc.java:218)
    at hudson.Launcher$LocalLauncher.launch(Launcher.java:930)
    at hudson.Launcher$ProcStarter.start(Launcher.java:450)
    at hudson.Launcher$RemoteLaunchCallable.call(Launcher.java:1299)
    at hudson.Launcher$RemoteLaunchCallable.call(Launcher.java:1260)
    at hudson.remoting.UserRequest.perform(UserRequest.java:205)
    at hudson.remoting.UserRequest.perform(UserRequest.java:52)
    at hudson.remoting.Request$2.run(Request.java:356)
    at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:72)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

This exception is odd, and difficult to understand. In my understanding, the cause of the error (invalid command) should be more clear, and ideally, validated sooner.

---

Originally reported by ealvarez, imported from: Process Launcher shouldn't throw ArrayIndexOutOfBoundException on empty command

• status: Reopened
• priority: Minor
• resolution: Unresolved
• imported: 2022/01/10

[timja]

dishitd:

Hi - I will like to work on this. However, I am unable to reporduce the issue. Can you please provide the steps to reproduce?

[timja]

ealvarez:

Here you have a test to reproduce it:

https://github.com/EstherAF/jenkins/commit/198e0a22c326f7d5a1c130deb56063592e646d41

[timja]

mramonleon:

dishitd I've been working on it for a while. Are you fine if I take care of it?

[timja]

dishitd:

Sure go ahead

[timja]

mramonleon:

The documentation of the ProcessBuilder class specified that the start method will return an IndexOutOfBoundsException if the command is the empty string, see the documentation here: https://docs.oracle.com/javase/8/docs/api/java/lang/ProcessBuilder.html#start--

IndexOutOfBoundsException - if the command is an empty list (has size 0)

So the behavior is the expected. The code sending this command is the one in charge to avoid that or capture the exception properly.

I will close this ticket becase as it is described, there is nothing to do generally.

[timja]

mramonleon:

Not sure about the right final status of the ticket

[timja]

ealvarez:

If this exception is expected, it is my understanding that its meaning should be documented, to allow the client to proactively check this failing condition.

[timja]

mramonleon:

It's documented: https://docs.oracle.com/javase/8/docs/api/java/lang/ProcessBuilder.html#start--

[timja]

ealvarez:

After talking with mramonleon, we agreed that:

• Given that the exception is documented in downstream jdk class (ProcessBuilder), it can have been handled already by some client, so changing this exception for another can have unexpected consequences in any plugin using hudson.Launcher
• ProcessBuilder is being used in several other classes in jenkins. To be consistent we should handle this exception equally, increasing the number of interface changes.

The objective is to make clearer the cause of this exception, so the least risky solution is:

• Showing a log before invoking the Launcher, when the command is empty, informing the user that this can cause unexpected behaviour.
  This should help any user to track down the cause of this exception in the future.
• Complete Launcher's javadoc informing about that a RuntimeException can be thrown because of that reason.

I'm creating a PR with these little changes