Fix showOnlyFailures for merged results

[d2weber]

Fixes https://issues.jenkins.io/browse/JENKINS-75332

Testing done

Manually verified in the "TAP Extended Test Results" that the Testpipeline respects showOnlyFailures

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                writeFile file: 'test1.tap', text: 'ok 1\nnot ok 2'
                writeFile file: 'test2.tap', text: 'ok 1\nnot ok 2'
            }
            post {
                always {
                    step $class: 'TapPublisher', testResults: 'test1.tap', showOnlyFailures: true, planRequired: false
                    step $class: 'TapPublisher', testResults: 'test2.tap', showOnlyFailures: true, planRequired: false
                }
            }
        }
    }
}

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[kinow]

Code looks alright to me, @d2weber. If you could write a unit test, then I'd just have a quick look with the IDE (to refresh on the code), otherwise, I can try to write one and update this branch/PR over next days and merge it.

Thanks!

[d2weber]

Yes no problem. I added a Unittest somewhat similar to TapPublisherTest::merged.

The hardest part in the process of creating the test was to figure out how to run the test properly. Only mvn clean install -Dtest=PublisherKeepsPropertiesTest seemed to work reliable for me. Other methods like mvn test -Dtest=.. or using VS Codes Java Test runner seemed to work at first but there was a subtle issue: only the first TapPublishers perform was actually called, because after successful completion of perform the execution of actions was interrupted by the Exception thrown in jenkins.model.Jenkins.getDescriptorOrDie.

[kinow]

Thank you, @d2weber !