Access JRI exception or trace from Java

[kenahoo]

If we call REngine.eval(REXP what, REXP where, boolean resolve) in Java, and the R command throws an exception (e.g. an explicit stop() or some other unanticipated condition), we currently get an REngineEvalException with the message "error during evaluation". How can we access the error message that R generates?

One technique I've been using goes something like this:

    REXP result = null;
    try {
        result = rengine.parseAndEval(expression);
    } catch (REngineException e) {
        // The REngineException for a syntax error typically only says "Parse error", so we include the code for context
        if (e.getMessage().equals("Parse error"))
            throw new REngineException(rengine, "Parse error in R code '" + expression + "'", e);
        if (e.getMessage().equals("error during evaluation")) {
            List<String> traceback = new ArrayList<>();
            for (Object o : rengine.parseAndEval("traceback()").asList()) {
                traceback.addAll(java.util.Arrays.asList(((REXPString) o).asStrings()));
            }
            throw new REngineException(rengine, "error during evaluation of R code:\n" + StringUtils.join(traceback, "\n"), e);
        }

        throw e;
    }

This is fairly brittle, because it depends on the specific error text, etc. Is similar information available somehow from the REngine, or if not, perhaps it could be added?

Thanks.