This is blocking as it prevents releasing (release:prepare).

Seems to be related to the mail thread Enforcer Plugin and Dependency Resolution.

are you using enforce-once? if so, this is deprecated in the next release as we can't make maven work correctly. In lieu of this, i added results caching to speed things up.

I was indeed using enforce-once. Using enforce now. Thanks.

I am having the same problem no matter if I use enforce-once or enforce. E.g. If I do "mvn eclipse:eclipse" the build fails if some reactor-dependency is NOT already installed in the local repository. When I remove the enforcer-plugin from my toplevel POM everything works well. This makes the enforcer-plugin useless since it causes more harm than it helps.

AFAIKT, this is not specific to the enforcer plugin.

The problem is that the eclipse plugin is running some lifecycle and thus kicking off the enforcer which requires maven to resolve dependencies that you may not have built yet. A workaround is to bind the enforcer to a phase like compile that is later than eclipse:eclipse kicks off.

Future plugin versions should probably use the new anno @requiresDependencyCollection.