Jenkins declarative pipeline expression with boolean environment variable - jenkins

Question

I'm using Jenkins declarative pipeline and I want to make a conditional step depending on an environment variable, which is set according the existence of a file.
So I just want to make something like that : if Dockerfile exist, perform next stage, else don't.
To perform this I tried :
pipeline {
// ...
stage {
stage('Docker') {
environment {
IS_DOCKERFILE = fileExists 'Dockerfile'
}
when {
environment name: 'IS_DOCKERFILE', value: true
}
stage('Build') {
// ...
}
}
}
}
Or :
pipeline {
// ...
stage {
stage('Docker') {
environment {
IS_DOCKERFILE = fileExists 'Dockerfile'
}
when {
expression {
env.IS_DOCKERFILE == true
}
}
stage('Build') {
// ...
}
}
}
}
In both cases, the Dockerfile exist and it is in the workspace. I also tried with strings ("true") but everytime, the pipeline continue without executing the stage 'Build'.
Any suggestions ?

Answer 1

This is because the exprsssion:
IS_DOCKERFILE = fileExists 'Dockerfile'
Creates the environment variable with boolean value as string:
$ set
IS_DOCKERFILE='false'
So the solution would be to use .toBoolean() like this:
environment {
IS_DOCKERFILE = fileExists 'Dockerfile'
}
stages {
stage("build docker image") {
when {
expression {
env.IS_DOCKERFILE.toBoolean()
}
}
steps {
echo 'fileExists'
}
}
stage("build libraries") {
when {
expression {
!env.IS_DOCKERFILE.toBoolean()
}
}
steps {
echo 'fileNotExists'
}
}
}

Answer 2

As #Sergey already posted, the problem is that you're comparing a string to a boolean. See fileExists: Verify if file exists in workspace.
Besides his answer, you can compare directly to a string:
environment {
IS_DOCKERFILE = fileExists 'Dockerfile'
}
stages {
stage("build docker image") {
when {
expression {IS_DOCKERFILE == 'true'}
}
steps {
echo 'fileExists'
}
}
stage("build libraries") {
when {
expression {IS_DOCKERFILE == 'false'}
}
steps {
echo 'fileNotExists'
}
}
}