I recently did a Gradle > Refresh Gradle Project that appeared to be a no-op: The operation which generally takes a while (in my large multi-project environment) completes immediately and the Eclipse projects were in fact not updated. I looked in the Eclipse “Error Log” view and saw this:
Synchronize Gradle projects with workspace failed due to an error while importing the root project.
It is indeed the case that the root project is closed, but this has never been a problem for me before. Then again, I updated to Eclipse 2018-12 recently. I’m running Buildship 3.0.0.v20181106-1441-m.