How to clear workspace in Jenkins pipeline before job starts

Question

I need to clear workspace before build starts. I tried using cleanDir() in stages, but in the declarative pipeline, check out happens first and when stage with cleadDir runs, checked out code also gets cleared which is not desired. How can we clear the workspace before check out in the declarative pipeline?

Answer 1

Actually, I have to revise my answer based on recent changes to the pipeline plugins, e.g. GitHub Branch Source Plugin 2.2.0 with JENKINS-43507.

Besides the different branch discovery behaviours, which can be configured, one can now define additional steps to take, including Clean before checkout (and Clean after checkout):

The resulting output in the pipeline execution will then be

Cleaning workspace
  > git rev-parse --verify HEAD # timeout=10
Resetting working tree
 > git reset --hard # timeout=10
 > git clean -fdx # timeout=10

so, pretty close to the calling git clean yourself.

Answer 2

stage('Git') {
            steps {
                step([$class: 'WsCleanup'])
                checkout scm
            }
        }

the WsCleanup does the trick