I am trying to create some shared library for Jenkins and after a very long journey I managed to almost finish it. Unfortunately at this point I am stuck with a very weird behaving / malfunctioning Jenkins instance.

All I need to achieve at last is to create some JSON string of a map with a nested list. Sounds trivial but seems highly problematic in a Jenkins shared library.

I have something like:

class SpecialJob implements Serializable {
    private class Entry {
        String name
        String description
    }

    def steps

    SpecialJob (steps) { this.steps = steps }
...
    def provide (Map args) {
        List<Entry> entries = new ArrayList<Entry>
        ... // Some code that adds entries to the list

        // The following clearly shows that there are items in the list
        // I get lines printed that show the content of the entries
        entries.each { entry ->
            steps.echo "Entry: ${entry.name} - ${entry.description}"
        }

        def content = [
            name: args.name,
            items: [buckets: entries]
        ]
        
        def jsonContent = JsonOutput.toJson (content)
        // Now in the Json, after the name: "items" : {"buckets": [{}]}}

The list buckets is always empty in the Json string. If I test the code standalone, without Jenkins, it works as expected. I have absolutely no clue why this happens. The same happens if I use steps.writeJSON – the list in the json string is empty.

To make sure: The list is not empty! The items in there get printed on the Jenkins console output, they are there.

I was already so frustrated that I thought I’ll just create that string myself. This doesn’t work as well, every quote I print in the string gets printed with the escaping backslash. So the following string in Jenkins:

String item = ""name": "${entry.descrition}""

Gets printed as "name": "Some description". Again, if I test the code outside Jenkins it works, the string contains the quotes correctly.

Can I somehow get this to work? All I want is a simple json string from this map.