This is a little hard to explain so I will try illustrate with an example. We have a subproject called "grails-datastore-gorm-mongo" that is defined in the same multiproject build as another subproject called "grails-datastore-gorm". The "grails-datastore-gorm-mongo" project declares a dependency on an external jar file not part of the multiproject build:

compile("org.grails:grails-plugin-domain-class:$grailsVersion")

This dependency transtively depends on "grails-datastore-gorm", which is as I said a project part of the multi project build. What happens is that Gradle actually downloads the published POM for the transitive dependency "grails-datastore-gorm", this is wrong because "grails-datastore-gorm" is part of the current multi-project build.

The result is a weird error such as

Execution failed for task ':grails-datastore-gorm-mongo:ideaModule'.
> Could not resolve all dependencies for configuration 'detachedConfiguration4'.
   > Module version group:org.grails, module:grails-datastore-gorm-mongo, version:1.2.0.RELEASE, configuration:detachedConfiguration4 declares a dependency on configuration 'signatures' which is not declared in the module descriptor for group:org.grails, module:grails-datastore-gorm, version:2.0.0.BUILD-SNAPSHOT

This is completely meaningless in describing the actual problem and had me digging into the bugs in the "signing" plugin. The solution for me was to go off and change the dependency declaration, for example:

compile("org.grails:grails-plugin-domain-class:$grailsVersion") {
    exclude group:"org.grails", module:"grails-datastore-gorm"
}
compile project(":grails-datastore-gorm")

Even though this is a solution, and allowed me to proceed this is wrong. I shouldn't have to exclude this transitive dependency as it is part of my current multi project build. I'm actually forced to provide wrong dependency configuration. The issue is compounded by the very bad error message which had me scratching my head for hours.