We are using maven for our builds, so in an effort to remove duplication, I created some variables that would set the value of a project's maven groupId and artifactId's like this:

${groovy:new XmlSlurper().parse("${vars.getValue('subversionCheckoutUrl')\}/pom.xml").groupId.text()}
${groovy:new XmlSlurper().parse("${vars.getValue('subversionCheckoutUrl')\}/pom.xml").artifactId.text()}

Because of our setup, the network administrators do not want the subversion repository available from the hosts on which our agents are running. The groupId and artifactId variables are used in creating the value for a variable named commandScriptUrl which was being used to get the value for the deployRoot.

We easily solved our problem by hard-coding the value for groupId and artifactId in the variables. It meant that we had to retain that data in two places, but its not terrible because those two values should almost never change.

With all of that being said, it would be nice if the QB server would log what variables it is unable to determine values for. When our build completed, the variables tab showed an empty value for deployRoot, but had no mention of groupId or artifactId. Nor was there any mention in either the server or agent log about the groupId or artifactId variables. If the server is unable to calculate a specific variable, then an error message should be logged explaining that. It would also be nice if on the variables page for a specific build instance if the error message was listed beside the variable name.