How to check if Jenkins Pipeline runs from a pull request?

Jenkins Multibranch Pipeline reacts to changes pushed to git branches.
Sometimes we want to determine if a specific run was executed for a pull request.
Here’s how to do it.

Run stage for any pull request

In this example, we want to run the Test stage from pull requests only.

pipeline {
    agent any
    stages {
        stage("Test") {
            when {
                changeRequest()
            }       
            steps {
                // ...
            }       
        }       
    }   
}

Run stage for a pull request to a specific branch

In this example, we want to run the Test stage only when the pull request is created with the develop branch as its target.

pipeline {
    agent any
    stages {
        stage("Test") {
            when {
                changeRequest target: "develop"
            }       
            steps {
                // ...
            }       
        }       
    }   
}

Run stage for a pull request created from a specific branch

In this example, we want to run the Test stage only when the pull request is created from the test branch.

pipeline {
    agent any
    stages {
        stage("Test") {
            when {
                changeRequest branch: "develop"
            }       
            steps {
                // ...
            }       
        }       
    }   
}

Run stage for a pull request created by specific user

In the final example, we want to run the Test stage only if the pull request was created by [email protected] user.

pipeline {
    agent any
    stages {
        stage("Test") {
            when {
                changeRequest authorEmail: "[email protected]"
            }       
            steps {
                // ...
            }       
        }       
    }   
}