NullPointerException when accessing build parameters on "Build with parameters" page using Groovy script

[j-ulrich]

I am using the Extensible Choice Parameter plugin and one of the parameters uses a Groovy script which tries to read the default values of another (hidden) parameter using the getParameters() method.
This throws a NullPointerException. Here is the relevant part of the stack trace:

Sep 04, 2014 4:03:15 PM jp.ikedam.jenkins.plugins.extensible_choice_parameter.SystemGroovyChoiceListProvider getChoiceList
Warnung: Failed to execute script
java.lang.NullPointerException
    at hudson.plugins.project_inheritance.projects.inheritance.InheritanceGovernor.getVersionedField(InheritanceGovernor.java:115)
    at hudson.plugins.project_inheritance.projects.inheritance.InheritanceGovernor.retrieveFullyDerivedField(InheritanceGovernor.java:182)
    at hudson.plugins.project_inheritance.projects.InheritanceProject.getAllProperties(InheritanceProject.java:2818)
    at hudson.plugins.project_inheritance.projects.InheritanceProject.getProperty(InheritanceProject.java:2953)
    at hudson.plugins.project_inheritance.projects.InheritanceProject.getParameters(InheritanceProject.java:3029)
    at hudson.plugins.project_inheritance.projects.InheritanceProject.getParameters(InheritanceProject.java:3025)
    at hudson.plugins.project_inheritance.projects.InheritanceProject$getParameters.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:42)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:112)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callSafe(AbstractCallSite.java:75)
    at Script1.run(Script1.groovy:4)

The problem occurrs because InheritanceGovernor calls InterhitanceProject.getVersionedObjectStore() (in getVersionedField()) but that returns null at that time. Since the project is not transient, the versionStore should not be null.

I tried calling onLoad(null, null) before getParameters() which seems to initialize the versionStore, although it throughs an IllegalStateException:

java.lang.IllegalStateException: no parent set on hudson.plugins.project_inheritance.projects.InheritanceProject[null]
    at hudson.model.AbstractItem.getParent(AbstractItem.java:170)
    at hudson.model.AbstractItem.getRootDir(AbstractItem.java:161)
    at hudson.plugins.project_inheritance.projects.InheritanceProject.getRootDir(InheritanceProject.java:952)
    at hudson.model.Job.getNextBuildNumberFile(Job.java:255)
    at hudson.model.Job.onLoad(Job.java:172)
    at hudson.model.AbstractProject.onLoad(AbstractProject.java:301)
    at hudson.model.Project.onLoad(Project.java:90)
    at hudson.plugins.project_inheritance.projects.InheritanceProject.onLoad(InheritanceProject.java:933)
    at hudson.model.Item$onLoad.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:42)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:120)
    at Script1.run(Script1.groovy:5)

Interestingly, this happens only on the "Build with parameters" page and not in the Jenkins script console or on the "Configure" page (it is possible to test the script there).

So the questions is:

• Why is the versionStore not correctly initialized when showing the "Build with parameters" page? And can this be fixed?

And for a possible workaround:

• What are the correct parameters to pass to onLoad()? I tried getParent() and getName() but getParent() returns null as well.