How to get updated environment variable value inside powershell script on Jenkins' declarative pipeline

Question

I am writing a Jenkins declarative pipeline script with a powershell script inside it. When I try to get the value of an environment variable inside powershell, I get its "original" value, as defined on the environment block, and not the value set in a previuous stage. The withEnv block doesn't work either. Example:

pipeline { 
    agent any 
    environment { TEST_ENV_VAR = "0" }
    stages {
        stage('stage1') { 
            failFast true
            parallel {
                stage('stage1.1') {
                    steps {
                        script {
                            TEST_ENV_VAR = "1"
                        }
                    }
                }
            }
        }
        stage('stage2') {
            failFast true
            parallel {
                stage('stage2.1') {
                    steps {
                        echo "$TEST_ENV_VAR" // prints "1"
                        withEnv(["inv_var = $TEST_ENV_VAR"]) {
                            withCredentials([usernamePassword(credentialsId: "$CredentialsID", passwordVariable: 'password', usernameVariable: 'srvUser')]) {
                                echo "$TEST_ENV_VAR" // prints "1"
                                echo "$env.inv_var" // prints "null"
                                powershell label: 'pshell', returnStatus: true, script: '''
                                    echo "$env:TEST_ENV_VAR"  # prints "0"                                  
                                    echo "$env:inv_var" # prints nothing
                                '''
                            }
                        }
                    }
                }
            }
        }
    }
}

Answer 1

It's a very simple answer, and very sad that groovy doesn't help more. Inside withEnv, you must not have a space between the variable and the equals sign. Here's your code with the credentials removed (because i don't have them), and the only other change is removing two spaces

pipeline { 
    agent any 
    environment { TEST_ENV_VAR = "0" }
    stages {
        stage('stage1') { 
            failFast true
            parallel {
                stage('stage1.1') {
                    steps {
                        script {
                            TEST_ENV_VAR = "1"
                        }
                    }
                }
            }
        }
        stage('stage2') {
            failFast true
            parallel {
                stage('stage2.1') {
                    steps {
                        echo "$TEST_ENV_VAR" // prints "1"
                        withEnv(["inv_var=$TEST_ENV_VAR"]) {

                                echo "$TEST_ENV_VAR" // prints "1"
                                echo "$env.inv_var" // now prints "1"
                                powershell label: 'pshell', returnStatus: true, script: '''
                                    echo "$env:TEST_ENV_VAR"  # prints "0"                                  
                                    echo "$env:inv_var" # now prints "1"
                                '''

                        }
                    }
                }
            }
        }
    }
}