Having hard time installing GWT plugin. Tried to search for GWT plugins and all I was able to find was GWT Imagebundle which is pretty outdated. Tried File Menu -> configure
Starting from the version 11 it's not possible to add PROJECT_FOLDER/src as it was described in the previously posted (by ctorx) link http://java.dzone.com/tips/gwt-development-intellij-idea. Once we add a source folder it appears as an "Empty library" and doesn't work. This is because IDEA treats it as a folder where should be compiled classes not sources.
But there is a workaround. To fix it we have to hack the module's IML file. Find the following lines in the IML file of your entry point module
and move your path into the CLASSES
tag, so the entire thing looks like the following