Grails 2.2.x and the problem with inner classes

in  Development, Grails, Java

We have been using Grails 2.2.x in some of our projects since it came out last year. Last week when I tried to upgrade another project because it was time to develop some new features I ran into a strange problem after upgrading from 2.1.3 to 2.2.1:

org.codehaus.groovy.grails.web.pages.exceptions.GroovyPagesException: Error processing GroovyPageView: Error executing tag : Error executing tag : java.lang.VerifyError: (class: com/troii/project/tags/SomeTag$Info, method: getSession signature: ()Ljavax/servlet/http/HttpSession;) Incompatible object argument for function call
	at com.googlecode.psiprobe.Tomcat70AgentValve.invoke(Tomcat70AgentValve.java:38)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:722)
Caused by: org.codehaus.groovy.grails.web.taglib.exceptions.GrailsTagException: Error executing tag : Error executing tag : java.lang.VerifyError: (class: com/troii/project/tags/SomeTag$Info, method: getSession signature: ()Ljavax/servlet/http/HttpSession;) Incompatible object argument for function call

I had never seen a java.lang.VerifyError exception before and the second strange thing was that the exception only occured when deploying the war in a tomcat not when starting the app with grails run-app.

Searching the web brought up some JIRA issues:

GRAILS-9627 inner class or enum in domain class breaks unit/integration testing
GRAILS-9784 Using an anonymous inner class in Controller causes VerifyError
GRAILS-10068 inner class in controller class breaks unit testing

and a blog post from someone who experienced the same issue.

Seems like with the update from Groovy 2.0.6 to 2.1.0 caused a compilation problem for inner classes. I had no chance to test with Grails 2.2.2 which was release three days ago but it seems the only workaround currently is to move the inner classe to external ones.

UPDATE: Seems Grails 2.2.2 improved a lot, at least for our project it works.