How to solve Groovy Unexpected input: @TimedInterrupt

I'm trying to execute the following groovy script by importing groovy class TimedInterrupt, unfortunately unable to comprehend the reason behind the compilation error. I have referred groovyOfficial documentation and have also looked at some resources here but could not make a significant progress. I would appreciate any valuable inputs from groovy experts in resolving this.

import groovy.transform.TimedInterrupt
import java.util.concurrent.TimeUnit

def buildInterrupt() {
    @TimedInterrupt(value = 3L, unit = TimeUnit.MICROSECONDS)
}

def timeout_method() {
    println 'This is for testing: '
}
 
buildInterrupt() //this invocation is necessary in the long run
time_method()

Post Execution
1 compilation error:

Unexpected input: '@TimedInterrupt(value = 3L, unit = TimeUnit.MICROSECONDS)\n}' at line: 6, column: 1

I need the timed interrupt to take effect and the expected output is below

Exception thrown

java.util.concurrent.TimeoutException: Execution timed out after 3 microseconds. Start time: Thu Mar 14 12:28:09 IST 2020
at timeout_method.run(timeout_method.groovy)

Thanks

Solution

I believe the reason you are running into compilation issues is that an annotation (TimedInterrupt in this case) needs to annotate a class, a member variable, a method, etc. In your case the annotation is applied in a location where it "has nothing to annotate".

The following code:

import groovy.transform.TimedInterrupt
import java.util.concurrent.TimeUnit

@TimedInterrupt(value = 500L, unit = TimeUnit.MILLISECONDS)
def somethingToAnnotate = 0

def methodA() {
  // sleep 100 ms
  100.times { Thread.sleep(1) }
  println 'hello from method a'
}

10.times { 
  methodA()
}

works and prints:

─➤ groovy solution.groovy
hello from method a
hello from method a
hello from method a
hello from method a
Caught: java.util.concurrent.TimeoutException: Execution timed out after 500 milliseconds. Start time: Fri Mar 26 12:11:14 CET 2021
java.util.concurrent.TimeoutException: Execution timed out after 500 milliseconds. Start time: Fri Mar 26 12:11:14 CET 2021
    at solution$_methodA_closure2.doCall(solution.groovy)
    at solution.methodA(solution.groovy:9)
    at solution$_run_closure1.doCall(solution.groovy:14)
    at solution.run(solution.groovy:13)

─➤

Here the annotation is applied to a variable.

It should be noted that in a groovy script, if you annotate a method, the timeout is started when the method is defined, not when it's executed. In other words, annotating a method and running the script will start the timeout even if the method is never run.