Jenkins Pipeline and stash Pull Request Builder not working on PR build / update

Below is the requirement required to achieve using Jenkins Pipeline and I am a new bee in Jenkins Pipeline.

• After completing development and pushing changes to Bitbucket, the user creates a pull request.

• To approve a pull request, we need at least one successful Jenkins build. Thus, we would only like to get the build result of the code checked for the pull request.

• When a pull request is created or updated, Jenkins is automatically launched for real continuous integration.

• The build result should be returned by Bitbucket.

Used by Stash Pull Request Builder and stash Notifier for the above process, which works for a regular Freestyle project.

We need to migrate similar functionality using Jenkins pipeline, so created a jenkins job as shown below. Pipeline script to check out PR branch and trigger build below

node {
    stage('Checkout') {         
        checkout(
        [
            $class: 'GitSCM',
            extensions: [               
                [$class: 'CleanCheckout'],              
            ],
            branches: [
                [name: '']
            ], 
            userRemoteConfigs: 
            [[
                credentialsId: 'id', 
                url: 'repourl.git'
                refspec: ('+refs/pull-requests/*/from:refs/remotes/origin/pr/*/from'), 
                branch: ('origin/pr/${pullRequestId}/from')

            ]]
        ])
    }

    stage('Build') {    
        sh 'make'
    }
    stage('notify') {
      step([$class: 'StashNotifier'])
        try {
        // Do stuff
        currentBuild.result = 'SUCCESS'     
    } catch(err) {
        currentBuild.result = 'FAILED'
    }
   step([$class: 'StashNotifier'])
 }
}

      

        
        
        
      

    

Although I did the above configuration, when I build / update the PR, the build does not automatically start in jenkins. I think the notification from butt to jenkins did not happen because we are specifying "origin/${pullRequestId}/from"

free style in the project. But I don't have this option to specify in a pipeline job.

Tried several alternatives as shown below.

Instead of stash Pull Request Builder, I only tried the SCM Poll project and set the cron job to run as "H/2 * * * *

". After the job is done, runs in jenkins. This means for every commit, a jenkins job is started. But Jenkins has to initiate a job when a PR is created / updated .

Also based on the question below, one answer says "In the freestyle job add a trigger to start with the pipeline as a build step" which I didn't find.

I'm missing something, of course, which might be basic and new to the jenkins pipeline.

Any hint of achieving the desired behavior?