I've been doing a bit of work on the TINKERPOP-1278 branch and have been mostly focused on generalizing/expanding the ScriptEngine infrastructure to gremlin-core. Seems like a weird place for ScriptEngine stuff to live as we've largely relegated such things to gremlin-groovy, but now that there are GLVs ScriptEngines have a role to play there that is core to TinkerPop and we rely on ScriptEngine instances in gremlin-core itself and as a result, it doesn't work too well if important aspects of ScriptEngines are left to gremlin-groovy.
The first important concept introduced in this work is the notion of a Gremlin-enabled ScriptEngine. Up until this point, the GremlinGroovyScriptEngine was just another ScriptEngine implementation, meaning that when loading it through the ScriptEngineManager, you got gremlin-groovy, nashorn, jython, etc. I've now established a separate GremlinScriptEngineManager: https://github.com/apache/tinkerpop/blob/073910598b8840a8e25f072371b304af322324f5/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/jsr223/GremlinScriptEngineManager.java This class very closely mimics the java ScriptEngineManager, but it only loads Gremlin-enabled ScriptEngine instance. It is worth noting that the java ScriptEngineManager will no longer load GremlinGroovyScriptEngine. As a result, I've removed "nashorn" from all the Gremlin Server config files as it creates errors otherwise. Now a Gremlin-enabled ScriptEngine is one that implements this interface (which is what makes it different than a regular java ScriptEngine): https://github.com/apache/tinkerpop/blob/073910598b8840a8e25f072371b304af322324f5/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/jsr223/GremlinScriptEngine.java I'm not sure that this will be the the final look of the interface, but just know that it's there. I also introduced the concept of a Customizer: https://github.com/apache/tinkerpop/blob/073910598b8840a8e25f072371b304af322324f5/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/jsr223/Customizer.java which is similar to the concept of a groovy CompilerCustomizer and allows us to provide a general way to supply configurations across all ScriptEngines (even those that are less robust that the groovy script engine). Gremlin Server is hooked up against all these changes at this point. The branch currently passes all integration tests so stuff appears to be working nicely. I did have to @Ignore a few unit tests because they used Nashorn and I was not sure of how to rectify that (tests probably just need to move elsewhere - I've made a note to come back to deal with that along with a whole ton of other notes - consider this a work in progress atm). Doing this work without breaking change has been hard as ScripEngine infrastructure is so critical to the upper end of the stack with both the console and gremlin server. I suspect that for 3.3.x there will be a wide batch of breaking change a'comin' to get this right. Thoughts/questions?
