Scripted pipeline: wrap stage - jenkins

Question

I would like to be able to wrap a 'stage' in Jenkins, so I can execute custom code at the start and end of a stage, so something like:
myStage('foo') {
}
I thought I could do this by using metaClass:
//Wrap stages to automatically trace
def originalMethod = this.metaClass.getMetaMethod("stage", null)
this.metaClass.myStage = { args ->
println "Beginning of stage"
println "Args: " + args
def result = originalMethod.invoke(delegate, args)
println "End of stage"
return result
}
But it appears the Groovy script itself is a Binding, which doesn't have a metaClass:
groovy.lang.MissingPropertyException: No such property: metaClass for class: groovy.lang.Binding
I'm still learning how Groovy and Jenkins Pipeline work, so perhaps I'm just missing something.

Answer 1

I am not familiar with the metaclass concept but I think that a simple solution to your problem is to define a wrapped stage as a function.
Here's an example of how you'd define such a function:
def wrappedStage(name, Closure closure) {
stage(name) {
echo "Beginning of stage"
def result = closure.call()
echo "End of stage"
return result
}
}
and this is how you would call it:
wrappedStage('myStage') {
echo 'hi'
}
The return value of wrappedStage would only make sense when the body of your stage actually returns something, for example:
If you call another job, eg:
wrappedStage('myStage') {
build job: 'myJob'
}
you will get back org.jenkinsci.plugins.workflow.support.steps.build.RunWrapper which you can use to access info of the job you run, like result, variables etc
If you print something to the console, eg:
wrappedStage('myStage') {
echo 'hi'
}
you will get back null.
Note that in my example I am not printing args because the way I understand stage, it only takes 2 arguments; the stage name and the closure it should run. The name of the stage will already be printed in the log, and I don't know how much value you'd get from printing the code you're about to execute but if that's something you want to do, take a look at this.
If you have a more specific case in mind for what you'd want to wrap, you can add more params to the wrapper and print all the information you want through those extra parameters.