Get variables from delegate scope in Groovy

Question

I'm trying to write a Jenkins Job DSL script and would like to write it as declaratively / DRY-ly as possible. The Jenkins task is calling some other tasks via a MultiJob. I have Groovy that originally looks like this (everything's contained within a class because it's referenced elsewhere):

static void buildDownstream(def parentJob, String commit_a="master",
    String commit_b="master") {
  parentJob.with {
    steps {
      phase('Phase') {
        job("name_1") {
          prop('COMMIT_A', commit_a)
          nodeLabel('NODE_LABEL', NODE_LABEL_MAP["name_1"])
          killPhaseCondition('NEVER')
        }
        job("name_2") {
          prop('COMMIT_A', commit_a)
          prop('COMMIT_B', commit_b)
          nodeLabel('NODE_LABEL', NODE_LABEL_MAP["name_2"])
          killPhaseCondition('NEVER')
        }
        job("name_3") {
          prop('COMMIT_A', commit_a)
          prop('COMMIT_B', commit_b)
          nodeLabel('NODE_LABEL', NODE_LABEL_MAP["name_3"])
          killPhaseCondition('NEVER')
        }
      }
    }
  }
}

I'd like to abstract out the job creation, which contains lots of duplication. I've ended up with something strange like this:

static void buildDownstream(def parentJob, String commit_a="master",
    String commit_b="master") {
  parentJob.with {
    steps {
      phase('Phase') {
        def phase = ({ owner })();
        { ->
          add_node_label=true;
          { ->
            commit_a = null;
            def self = ({ owner })();
            addJob("name_1", self).call(phase);
          }
          def self = ({ owner })();
          addJob("name_2", self).call(phase);
          addJob("name_3", self).call(phase);
        }
      }
    }
  }
}

private static Closure addJob(String job_name, Closure callingClosure) {
  return { phase ->
    def job_config = {
      if(commit_a != null) {
        prop('COMMIT_A', commit_a)
      }
      if(commit_b != null) {
        prop('COMMIT_B', commit_b)
      }
      if(add_node_label == true) {
        nodeLabel('NODE_LABEL', NODE_LABEL_MAP[job_name])
      }
      killPhaseCondition('NEVER')
    }

    job_config.delegate = callingClosure
    job_config.resolveStrategy = Closure.DELEGATE_ONLY
    phase.job(job_name, job_config)
  }
}

which, probably being totally non-idiomatic Groovy (all this def self = ({ owner })() stuff doesn't sit right with me), doesn't work at all.

Basically, I want to pass all the variables in callingClosure's scope to the job_config closure without explicitly passing all of them in as arguments. (Explicitly passing a map of arguments works, but it gets unwieldy when there are lots of arguments.) How can I do this?

(P.S: Currently, Groovy is trying to resolve the commit_a variable inside job_config as coming from javaposse.jobdsl.dsl.helpers.step.PhaseContext, which I find strange; didn't I explicitly set the delegate to a closure inside that PhaseContext?)

EDIT: From another SO question, it appears that I can set phase = delegate (which defaults to owner?) instead of ({ owner })() and be fine; I don't really get this either, since job is a property of the PhaseContext, and not its parent (?)

If you want to access variables, why dont you just pass the closure as a parameter? Also closures naturally have access to their owners variables. I posted a question about delegates just a bit ago, maybe it helps you: http://stackoverflow.com/questions/32368483/groovy-delegates-working-as-intended — PhilBa, Sep 03 '15 at 10:40
Thanks for the suggestion! I ended up doing something similar (just passed all the parameters as a map). — jiangty, Sep 03 '15 at 23:32

score 0 · Accepted Answer · answered Sep 03 '15 at 23:31

Well, I ended up not trying to ask Groovy to implicitly resolve variables from the delegate context, and instead just passed in the parameters in a map.

static void buildDownstream(def parentJob, 
    String commit_a="master", String commit_b="master") {
  parentJob.with {
    steps {
      phase('Tests') {
        def params = [COMMIT_A:commit_a] 
        this.getTestJob(delegate, "name_1", params)
        params.COMMIT_B = commit_b
        this.getTestJob(delegate, "name_2", params)
        this.getTestJob(delegate, "name_3", params)
        continuationCondition('ALWAYS')
      }
    }
  }
}

private static void getTestJob(def phase, String job_name, 
    Map properties) {
  phase.job(job_name) {
    properties.each { k, v -> prop(k, v) }
    killPhaseCondition('NEVER')
  }
}

One problem with my original method was that I was trying to access local variables in the closures, but that requires the closure to be evaluated; that turns out to be really weird, and I guess I should just not try to do that.

Get variables from delegate scope in Groovy

1 Answers1