Jenkins pipeline fails with bad substitution error on file read

Question

I am writing a scripted pipeline as part of multibranch pipeline in which I need to read a key-value pairs from a JSON file. When I run the pipeline I am getting the following error: /home/jenkins/workspace/dMyproject-QRMU74PK33RGCZRTDPVXCWOT55L2NNSXNPY2LJQ5R2UIIYSJR2RQ@tmp/durable-c4b5faa2/script.sh: Bad substitution

Doing a little research of my code I found out that particulary this line is causing the error:

String fileContents = new File( ".env" ).text;

But I cant find out, what's exactly wrong. My env file looks like this:

{
"key" :"value",
"key2" :"value2"
}

import groovy.json.JsonSlurper
import java.io.File 


node('google-cloud-node') {
   dockerfile {
      filename 'BuildDockerfile'
    }
    currentBuild.result = "SUCCESS"
    try {
        String dockerFileName = "BuildDockerfile"
        def customImage = docker.build("my-image:${env.BUILD_ID}","-f ${dockerFileName} .")

        customImage.inside('-u root') {
            stage('Checkout'){
                checkout scm
            }
            stage('Build'){
              notify("#test-ci-builds","Oh, time to  build something!")
                sh '''
                set +x
                whoami
                pwd
                npm install
                npm build
               '''
             }
             stage('Deploy') {
                        parseArgsFile()
                        withCredentials([file(credentialsId: "scanner-dev-ssh-service-account", variable: 'ID')]) {
                            sh '''
                              set +x
                              gcloud auth activate-service-account jenkins-test1@scanner-dev-212008.iam.gserviceaccount.com --key-file=$ID  --project=scanner-dev-212008
                              gcloud compute --project scanner-dev-212008 ssh --zone us-west2-a ubuntu@docker-slave --command "uname -a"
                            '''
                        }
             }
         }
    }
    catch (err) {
        notify("#test-ci-builds","Oh, crap!")
        currentBuild.result = "FAILURE"
            sh 'echo  ${env.BUILD_URL}'
        throw err
    }

}

def notify(channel,text) {
  slackSend (channel: "${channel}", message: "${text}", teamDomain: "distillery-tech", token: "0W6205gwiR1CEVOV4iMFiNQw")
}

def parseArgsFile(params=null){

    String fileContents = new File( ".env" ).text;
    def InputJSON = new JsonSlurper().parseText(inputFile.text)
    InputJSON.each{ println it }
}

Answer 1

Short answer

Instead of using new File and JsonSlurper simply use the readJSON step.

Long answer

There‘s more than one issue in your script:

1. You cannot use File objects in the Pipeline. In fact you could but those files would always get referenced on the Jenkins master and would require to have the sandboxing disabled. You cannot read files from a build agent using a File object. Instead, use the Pipeline step readFile
2. JsonSlurper cannot be used in plain Pipeline code as it doesn’t implement the Serializable interface. You would need to encapsulate everything inside a @NonCPS method. However you should not do that either as @NonCPS code cannot be aborted or continued after a restart and there’s the readJSON Pipeline utility step.