update_appspec_jenkins.groovy

// This code should allow you to update the different fields in the appspec.yml for AWS Code Deploy.
// Updating the source file location is just an example. All paramaters can be edited.
// readYaml and writeYaml come from the pipline-utility-steps-plugin (https://github.com/jenkinsci/pipeline-utility-steps-plugin)
void updateAppspec(String newFile) {
  // By default reads from the working directory
  String appspecFile = "appspec.yml"
  Map data = readYaml file: appspecFile
  String destination = data.files[0].destination
  // files is a ArrayList
  data.files.set(0, ["source":newFile, "destination": "${destination}"])
  // Reove appspec file before writing otherwise it will not work.
  sh "rm -f ${appspecFile}"
  writeYaml file: appspecFile, data: data
  // verify value has been updated
  Map newYml = readYaml file: appspecFile
  assert newYml.files[0].source == newFile
}

def call(Map config) {
  // declerative pipeline
  pipeline {
    agent any
    stages {
      stage('Update appspec'){
        steps{
          updateAppspec('newSourceFile')
        }
      }
    }
  }
}