I've just booted up a fresh install of Eclipse Neon, downloaded the latest versions of Xtext, Eclipse Facets and ANTLR 4, which gives me a full language and plugin compiler for Eclipse (using Xtext).
I have built my mwe2 workflow for the main project, have clicked on the plugin.xml of the ui project, pressed "Launch an Eclipse Application" to test the grammar, and all of a sudden pops up a small box stating:
Cannot locate JRE definition: "J2SE-1.8". Launch aborted."
Absolutely no stack trace or anything. Just this ambiguous line...
I am using this fresh install on my Windows computer, because the exact same error, word-for-word shows up on my Mac. I have my Java installed fine on both, using the latest versions of 1.8, so there must be something wrong with either Java itself, Xtext, or Eclipse.
What do I do!?
This is a bug in Xtext: https://github.com/eclipse/xtext-core/issues/273
Workaround (1): Open generated launch config an replace J2SE-1.8 with JavaSE-1.8
Workaround (2): Chose Debug, Debug Configureations ..., Debug (will autorepair the launch config)