Re: Jelly Errors / Debug Advice?

Thanks for filing this as a bug, and here's how you usually debug this.

First, the ultimate root cause of this is NPE in Hudson code.

> java.lang.NullPointerException
>         at hudson.Functions.isMultiline(Functions.java:312)
>         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

Then Jelly reports that as:

> > [WARN] JexlExpression - -Caught exception evaluating: h.isMultiline(
> > attrs.value). Reason: java.lang.NullPointerException <
> > java.lang.NullPointerException>

... so you know where (although limited) the exception happened. I guess 
it would be really nice if Jelly can report the file name and line 
number where this happened, and all the jelly script "call stack" 
leading up to this point --- I'll see if I can make that change.

In the mean time, if you need that information, you either needs to run 
this in the debugger (the doc contains an explanation of how to do it.) 
Or often a simple grepping gets you where you have the code.

Eric Crahen wrote:
> I'm venturing into writing plugins for the first time, so I'm just starting
> to learn how the global.jelly and config.jelly's work. This is my first time
> playing with jelly so its all a learning experience for me.
>
> After activating the HelloWorld plugin, I've noticed that when I go into the
> Job Configuration screen, it renders correctly - but I sometimes see the
> error below depending on what I've done to the file. For example, if I
> comment out the body of the xml so its just the opening and closing j:jelly
> tag, or if I actually remove the configure.jelly file altogether. I only
> know the problem has to do with this file because of the screen it happens
> on and when I see errors on stderr (and because I'm only changing one thing
> at a time)
>
> > From the error, I really don't know what is wrong - or what file is there. I
> can deduce the file with the problem through the means above, but I haven't
> yet learned what is expected. I'm guessing it must be the missing f:entry
> tag. I'll figure it out shortly, but I'm wondering if there are some
> techniques to better debug this kind of stuff that you've developed through
> your experience in creating the built-in jelly components?


--
Kohsuke Kawaguchi
Sun Microsystems                   kohsuke.kawaguchi@xxxxxxx

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