Getting error while deleting Jenkins build history - jenkins

Question

Hello All I am getting below error while deleting build history of jenkins jobs
No build logs found in calcmanager-pull-request and build history count is : 0
[Pipeline] End of Pipeline
java.lang.NullPointerException: Cannot invoke method getLastBuild() on null object
Below is the pipeline script I am using. calcmanager-pull-request job contains build history but it is displaying as zero
pipeline {
agent { label 'master' }
stages {
stage('delete all jobs build history'){
steps {
script {
def buildLogCount=10
Jenkins.instance.getAllItems(Job.class).each { jobitem ->
def jobName = jobitem.name
def jobInfo = Jenkins.instance.getItem(jobName)
if(jobInfo.getLastBuild()){
def lastBuildNum=jobInfo.getLastBuild().getNumber()
if(lastBuildNum>=buildLogCount){
def deletedBuildNum=lastBuildNum - buildLogCount
def deletedNumRange = Fingerprint.RangeSet.fromString("0-${deletedBuildNum}",false);
def buildCount=jobInfo.getBuilds(deletedNumRange).size()
if(buildCount==0){
println "No build logs found in ${jobName} and build history count is : ${buildCount}"
}
else{
jobInfo.getBuilds(deletedNumRange).each { item ->
item.delete()
}
}
}
else{
println "No build logs to delete in ${jobName}"
}
}
else{
println "No build logs found in ${jobName}"
}
}
}
}
}
}
}
}

Answer 1

You got that error due to some of jobs was never run. It doesn't have history.
So you can build a List with jobs with history:
Jenkins.instance.getAllItems(Job.class)
.findAll { it.getLastBuild()?.getNumber() } // if job doesn't not history it will return null == false
.each { job ->
def lastBuildNum=job.getLastBuild().getNumber()
/// you code is here
}

Answer 2

Above code works fine if you don't have any multi branch pipeline jobs. If you have multibranch pipeline jobs then use below code in jenkins file.
properties(
[
buildDiscarder(logRotator(daysToKeepStr: '60', numToKeepStr: '7')),
]
)