Jenkins pipeline: use of a global variable within the pipeline - jenkins-pipeline

Question

I've got a Jenkins pipeline with multiple stages, that will need to know how the build was triggered (by user, timer, etc.) and I'd like to avoid having to duplicate the following line in each stage:
currentBuild.rawBuild.getCauses()[0].class.getName().contains('TimerTriggerCause')
When using that command in each when blockm it works as expected, but when placed in the environment block it keeps failing:
[Pipeline] node
Running on Jenkins in /var/lib/jenkins/jobs/test-pipeline/workspace
[Pipeline] {
[Pipeline] withEnv
[Pipeline] {
[Pipeline] stage
[Pipeline] { (Stage on timer)
[Pipeline] }
[Pipeline] // stage
[Pipeline] }
[Pipeline] // withEnv
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
java.lang.NoSuchMethodError: No such DSL method '$' found among steps [archive, bat, build, catchError...zip] or globals [currentBuild, docker, env, params, pipeline, scm]
at org.jenkinsci.plugins.workflow.cps.DSL.invokeMethod(DSL.java:199)
at org.jenkinsci.plugins.workflow.cps.CpsScript.invokeMethod(CpsScript.java:122)
at sun.reflect.GeneratedMethodAccessor513.invoke(Unknown Source)
Jenkins script:
pipeline {
agent {
label 'master'
}
environment {
DAY = Calendar.getInstance().get(Calendar.DAY_OF_WEEK)
HOUR = Calendar.getInstance().get(Calendar.HOUR_OF_DAY)
ONTIMER = currentBuild.rawBuild.getCauses()[0].class.getName().contains('TimerTriggerCause')
}
stages {
stage('Stage on timer') {
when {
expression {
return (${ONTIMER} && (${DAY} != Calendar.SATURDAY && ${DAY} != Calendar.SUNDAY))
}
}
steps {
echo "on timer..."
}
}
}
}
The 2 other variables DAY and HOUR do work fine when used in the when block. Any idea?

Answer 1

After some more trial and error, I got the behaviour I wanted.
The when condition when dealing with environmental variables uses a slightly different syntax. It has its own environment keyword to use then:
when {
environment name: 'ONTIMER', value: 'true'
}
As a bonus, using integer value as well in the when block:
when {
allOf {
environment name: 'ONTIMER', value: 'true'
expression { return Integer.parseInt(env.HOUR) < 11 }
}
}
Even better, it's possible to use the triggeredBy keyword and act on this:
when {
anyOf {
expression { return params.RUN }
allOf {
triggeredBy "TimerTrigger"
expression {
Integer.parseInt(env.HOUR) < 13
}
}
}
}
Values to be used with triggeredBy include:
TimerTrigger
UserId
(others? like SCM trigger?)