I know this is old, but I see no answers. Since I cannot find my answer, I'll probably have to formulate a new question, but I wanted to point out to the last commenter, nmrao, that ${projectDir} is mentioned in the ReadyAPI documentation... here's a link to one page I found today:
https://support.smartbear.com/readyapi/docs/configure/workspaces/properties.html
excerpt:
To use the file path relative to the project directory, use ${projectDir}\data. For example:
D:\projects\webservice\data\testdata.xls
To use the file path relative to the directory that contains the workspace file, use ${workspaceDir}\data. For example:
D:\projects\data\testdata.xls
Were you also using a relative path for WADL with ${projectDir}?
The project folder was resolved correctly when testing a groovy script like this
log.info context.expand('${projectDir}')
log.info context.expand('${workspaceDir}')
