How do you handle global variables in a declarative pipeline? - jenkins

Question

Previously asked a question about how to overwrite variables defined in an environment directive and it seems that's not possible.
I want to set a variable in one stage and have it accessible to other stages.
In a declarative pipeline it seems the only way to do this is in a script{} block.
For example I need to set some vars after checkout. So at the end of the checkout stage I have a script{} block that sets those vars and they are accessible in other stages.
This works, but it feels wrong. And for the sake of readability I'd much prefer to declare these variables at the top of the pipeline and have them overwritten. So that would mean having a "set variables" stage at the beginning with a script{} block that just defines vars- thats ugly.
I'm pretty sure I'm missing an obvious feature here. Do declarative pipelines have a global variable feature or must I use script{}

Answer 1

This is working without an error,
def my_var
pipeline {
agent any
environment {
REVISION = ""
}
stages {
stage('Example') {
steps {
script{
my_var = 'value1'
}
}
}
stage('Example2') {
steps {
script{
echo "$my_var"
}
}
}
}
}

Answer 2

Like #mkobit says, you can define the variable to global level out of pipeline block. Have you tried that?
def my_var
pipeline {
agent any
stages {
stage('Example') {
steps {
my_var = 'value1'
}
}
stage('Example2') {
steps {
printl(my_var)
}
}
}
}

Answer 3

For strings, add it to the 'environment' block:
pipeline {
environment {
myGlobalValue = 'foo'
}
}
But for non-string variables, the easiest solution I've found for declarative pipelines is to wrap the values in a method.
Example:
pipeline {
// Now I can reference myGlobalValue() in my pipeline.
...
}
def myGlobalValue() {
return ['A', 'list', 'of', 'values']
// I can also reference myGlobalValue() in other methods below
def myGlobalSet() {
return myGlobalValue().toSet()
}

Answer 4

#Sameera's answer is good for most use cases. I had a problem with appending operator += though. So this did NOT work (MissingPropertyException):
def globalvar = ""
pipeline {
stages {
stage("whatever) {
steps {
script {
globalvar += "x"
}
}
}
}
}
But this did work:
globalvar = ""
pipeline {
stages {
stage("whatever) {
steps {
script {
globalvar += "x"
}
}
}
}
}

Answer 5

The correct syntax is:
For global static variable
somewhere at the top of the file, before pipeline {, declare:
def MY_VAR = 'something'
For global variable that you can edit and reuse accross stages:
At the top of your file, add an import to Field:
import groovy.transform.Field
somewhere before pipeline {, declare:
#Field def myVar
then inside your step, inside a script, set the variable
stage('some stage') {
steps {
script {
myVar = 'I mutate myVar with success'
}
}
}
to go even further, you can declare functions:
before the pipeline {
def initSteps() {
cleanWs()
checkout scm
}
and then
stages {
stage('Init') {
steps {
initSteps()
}
}
}

Answer 6

This worked for me
pipeline {
agent any
stages {
stage('Example') {
steps {
script{
env.my_var = 'value1'
}
}
}
stage('Example2') {
steps {
printl(my_var)
}
}
}
}