jenkins extended parameter plugin groovy script

Question

The website for the plugin says that you can create a groovy script to run to determine the parameter list.

how is this resolved though? The instructions don't say anything.

1. In what context is the script run?
2. What am i supposed to return from the script?
3. What directory is the cwd of the script? is it the environment variable WORKSPACE?
4. there is an extra field called variable bindings . How is this used?

Answer 1

I had to dig into the source code to find the answer to these questions so i hope this helps everyone else.

1. In what context is the script run?

The script is run inside a groovy.lang.GroovyShell. This class is currently from the Groovy 1.8.5 library. here is an excerpt from the code:

// line 419 - 443 of the ExtendedChoiceParamaterDefinition
else if(!StringUtils.isBlank(groovyScript)) {
    try {
        GroovyShell groovyShell = new GroovyShell();
        setBindings(groovyShell, bindings);
        Object groovyValue = groovyShell.evaluate(groovyScript);
        String processedGroovyValue = processGroovyValue(isDefault, groovyValue);
        return processedGroovyValue;
    }
    catch(Exception e) {

    }
}
else if(!StringUtils.isBlank(groovyScriptFile)) {
    try {
        GroovyShell groovyShell = new GroovyShell();
        setBindings(groovyShell, bindings);
        groovyScript = Util.loadFile(new File(groovyScriptFile));
        Object groovyValue = groovyShell.evaluate(groovyScript);
        String processedGroovyValue = processGroovyValue(isDefault, groovyValue);
        return processedGroovyValue;
    }
    catch(Exception e) {

    }
}

2. What am i supposed to return from the script?

As the above code demonstrates, the script should return a string with whatever delimiter you have specified in the paramater or a String[] array. here is a snippet of the function that processes the value returned from the script:

// line 450 - 465 of ExtendedChoiceParameterDefinition
private String processGroovyValue(boolean isDefault, Object groovyValue) {
    String value = null;
    if(groovyValue instanceof String[]) {
        String[] groovyValues = (String[])groovyValue;
        if(!isDefault) {
            value = StringUtils.join((String[])groovyValue, multiSelectDelimiter);
        }
        else if(groovyValues.length > 0) {
            value = groovyValues[0];
        }
    }
    else if(groovyValue instanceof String) {
        value = (String)groovyValue;
    }
    return value;
}

3. What directory is the cwd of the script? is it the environment variable WORKSPACE?

Does it matter? You can access the environment variable WORKSPACE from within the script using

Map<String, String> props = System.getenv();
def currentDir = props.get('WORKSPACE');

4. there is an extra field called variable bindings. How is this used?

This is a property file formatted key=value file. these names are then resolvable in the groovy script.

    e.g.
    key1=foo
    prop2=bar

Answer 2

For parse json object (from parametres) to groovy object - Parsing and producing JSON

import groovy.json.JsonSlurper
def jsonSlurper = new JsonSlurper()
def object = jsonSlurper.parseText('{ "myList": [4, 8, 15, 16, 23, 42] }')
println(object.myList)