Allow multiline String in xtext grammar to embed javascript code

Question

I am writing a small "language" to create javascript code. Essentially it is hiding/showing some html form elements. But i need to add custom javascript code to some, e.g. what to do on a click-event.

Action:
  'on' eventName=ID 'do' code=CODE
;

terminal BEGIN: "!$";
terminal END: "$!";

terminal CODE:
  BEGIN -> END
;

I can now create an Eclipse-Plugin and code in my language, but the value of the field code contains the BEGIN and END characters.

on eventName do !$
    var x = thisIsJavaScript();
    console.log(x); 
$!

My value is:

!$
var x = thisIsJavaScript();
console.log(x);             
$!

I want only the part in between without !$ and $!.

Any hint is appreciated.

Thank you very much!

Answer 1

you should write a valueconverter for your terminal rule

import org.eclipse.xtext.common.services.DefaultTerminalConverters;
import org.eclipse.xtext.conversion.IValueConverter;
import org.eclipse.xtext.conversion.ValueConverter;
import org.eclipse.xtext.conversion.ValueConverterException;
import org.eclipse.xtext.nodemodel.INode;

import com.google.inject.Inject;

public class MyDslConverters extends DefaultTerminalConverters {

    @Inject
    private CODEValueConverter codeValueConverter;

    @ValueConverter(rule = "CODE")
    public IValueConverter<String> CODE() {
        return codeValueConverter;
    }

    public static class CODEValueConverter implements IValueConverter<String> {

        @Override
        public String toValue(String string, INode node) throws ValueConverterException {
            return string.substring(2, string.length()-2);
        }

        @Override
        public String toString(String value) throws ValueConverterException {
            return "!$" + value + "$!";
        }

    }

}