It would be great if STS could provide some functionality to download and attach the source jars of dependencies, retrieved though ivy - similar to what m2eclipse can do with maven.
grails-plugins often provide additional libraries which are retrieved by ivy. it would be great to have some functionality to attach also the source jars automatically.
m2eclipse provides similar functionalities by right-click / download sources + download javadoc.
I have to retrieve the source artifacts (which I usually do through some dummy-maven-project) and attach every source jar i need manually.
In my actual setup (STS 2.5.1) a restart is also needed to make the attached source work. Don't know if its just my setup or a bug. If someone can commit this, i can post an issue-report for this.