如何使用 Jenkins 声明式语法管道将 JSON 对象捕获为美化字符串？

pipeline {
  agent any

  stages {

    stage( "Set up" ) {
      steps {
        script {
          hostname    = "bld-machine"
          reply_email = "jenkins@${hostname}.company.com"
          actor_email = "[email protected]"
          status_json = initStatusJson()
        }
      }
    }

    /** Try figure out the difference between "global" and "env." variables. */
    stage( "Capture variables" ) {
      steps {
        script {
          status_json.env["var"]  = "${env.var}" as String
          status_json.env["var2"] = "${var}" as String
        }
      }
    }
  }

  post {
    always {
      script {
        def pretty_json = writeJSON( returnText: true, json: status_json )
      }
      emailext( subject: "CI/CD | ${currentBuild.currentResult}",
                from: "${reply_email}",
                to: "${actor_email}",
                mimeType: "text/plain",
                body: "${pretty_json}" )
    }
  }
}

def initStatusJson() {
  def json_obj = readJSON text: '{}'
  json_obj.job = readJSON text: '{}'
  json_obj.env = [:]
  json_obj.job.name = "${JOB_BASE_NAME}" as String
  json_obj.job.number = "${BUILD_ID}" as String
  json_obj.job.server = "${JENKINS_URL}" as String
  json_obj.job.visualization = "${JENKINS_URL}/blue/organizations/jenkins/${JOB_BASE_NAME}/detail/${JOB_BASE_NAME}/${BUILD_ID}/pipeline" as String

  return json_obj
}

上述 Jenkinsfile 中的 def pretty_json =... 语句触发以下错误：

WARNING: Unknown parameter(s) found for class type WARNING: Unknown parameter(s) found for class type 'org.jenkinsci.plugins.pipeline.utility.steps.json.WriteJSONStep': returnText
[Pipeline] }
[Pipeline] // script
Error when executing always post condition:
java.lang.IllegalArgumentException: You have to provided a file for writeJSON.
    at org.jenkinsci.plugins.pipeline.utility.steps.json.WriteJSONStepExecution.run(WriteJSONStepExecution.java:61)
    at org.jenkinsci.plugins.pipeline.utility.steps.json.WriteJSONStepExecution.run(WriteJSONStepExecution.java:43)
    at org.jenkinsci.plugins.workflow.steps.SynchronousNonBlockingStepExecution.lambda$start$0(SynchronousNonBlockingStepExecution.java:47)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

我尝试过的方法：

1. def pretty_json = writeJSON( returnText: true, json: status_json ) 语句的灵感来自以下资源：
   Jenkinsfile 管道构造 JSON 对象并写入文件
   https://www.jenkins.io/doc/pipeline/steps/pipeline-utility-steps/#writejson-write-json-to-a-file-in-the-workspace

2. 我还尝试了 def pretty_json = writeJSON returnText: true, json: status_json ，结果出现了相同的错误。

3. status_json.toString() 返回有效但未美化的 JSON 字符串。

4. 我尝试了 def pretty_json = JsonOutput.toJson(status_json) ，基于 在 Jenkins Pipeline 中从 Groovy 变量创建 JSON 字符串 ，并生成此错误：

Error when executing always post condition:
groovy.lang.MissingPropertyException: No such property: JsonOutput for class: groovy.lang.Binding

5. 尝试基于 https://gist.github.com/osima/1161966 的 def pretty_json = groovy.json.JsonOutput.prettyPrint(status_json) ，并生成此错误错误：

Error when executing always post condition:
groovy.lang.MissingMethodException: No signature of method: java.lang.Class.prettyPrint() is applicable for argument types: (net.sf.json.JSONObject)

更新： 尝试了 @daggett 的解决方案，如下所示：

  post {
    always {
      script {
        def pretty_json = status_json.toString(2)
      }
      emailext( subject: "CI/CD | ${currentBuild.currentResult}",
                from: "${reply_email}",
                to: "${actor_email}",
                mimeType: "text/plain",
                body: "${pretty_json}" )
    }
  }

...还尝试了一些变体，例如 pretty_json = ... （而不是 def pretty_json = ... ），还将 pretty_json 赋值移到了 script{... 范围之外...但都不起作用。

在 script{... 上下文中， .toString(2) 生成了此错误：

Scripts not permitted to use method net.sf.json.JSON toString int.

在 script{... 上下文之外，它生成了我所理解的“语法错误”：

WorkflowScript: 79: Expected a step @ line 79, column 7.
         pretty_json = status_json.toString(2)