A and B are strings, yet you are checking them against true?

I guess it got solved.

I did two things :
1. Restarted Jenkins.
2. There was another script before which had some print command afte the line cancel=true and I read somewhere that cancel=true has to be the last line in the script. Well now this is a bug that cancel=true works only if it is the last line. Still I got it working for now that way.

A and B are boolean variables which are of string values true and false (as mentioned in the help function for boolean variables. Also I could see it print and not print depending on values of A and B so that is working.

Without looking at the sources, this looks a lot like the return value of the script is used rather than the value of the cancel variable?

Thanks for the prompt replies. I would say it is still a issue that it works only if cancel=true is the last line in the script. Assume everything else is working just fine.

I am not using any return variable from the script. I just wanted email sending to be cancelled when I set cancel to be true. However, seeing this kind of behaviour it does indicate that the email sending does not solely depend on cancel variable for plugin Or it get over ridden by something fishy in during compilation.

This is how the plugin gets the value of "cancel"

Object output = shell.evaluate(script);
if (output != null) {
    pw.println("Result: " + output);
    cancel = ((Boolean) shell.getVariable("cancel"));
    debug(context.getListener().getLogger(), "Pre-send script set cancel to %b", cancel);
}

The unit tests show that setting cancel to true work, so something else is possibly interfering.

The issue is actually in the code I pasted before. If the last line doesn't evaluate to some value, the output variable will be set to null and the value of cancel will never be updated. This will be fixed in the next version.

Code changed in jenkins
User: Alex Earl
Path:
src/main/java/hudson/plugins/emailext/ExtendedEmailPublisher.java
src/test/java/hudson/plugins/emailext/ExtendedEmailPublisherTest.java
http://jenkins-ci.org/commit/email-ext-plugin/27fbded960faec271591a284709dad6dde3af4c0
Log:
Fix JENKINS-27448

Remove check for output != null.

Removed check for null that caused the cancel value to not be updated.