Message from toString() is still missing for me though. It could be that we're doing something wrong.

We're running it via JSR223 but actually the problem is more general.

Trivial example via the JSR223 script engine:

public void testJRubyError() throws Exception { ScriptEngineManager manager = new ScriptEngineManager(); manager.getEngineByExtension("rb").eval("raise 'Test'"); }

Outputs:

javax.script.ScriptException: org.jruby.exceptions.RaiseException
at com.sun.script.jruby.JRubyScriptEngine.evalNode(JRubyScriptEngine.java:456)
[cutting rest as script engine stack trace is irrelevant]
Caused by: org.jruby.exceptions.RaiseException

So certainly when being printed as a nested exception nothing is showing. But while playing around with other stuff I discovered that it did somewhat work doing it directly:

public void testJRubyError() throws Throwable {
ScriptEngineManager manager = new ScriptEngineManager();
try { manager.getEngineByExtension("rb").eval("raise 'Test'"); } catch (ScriptException e) { throw e.getCause(); }
}

Output:
org.jruby.exceptions.RaiseException
<unknown>:1: Test (RuntimeError)
...internal jruby stack elided...
...internal jruby stack elided...

My intuition says that whereas printStackTrace() has been overridden in RaiseException, this is not what the outer method is calling (I'm guess it's calling getStackTrace() itself... and I bet overriding that is a more foolproof solution than overriding printStackTrace() anyway.)

The ideal output as I see it would be something like:

javax.script.ScriptException: org.jruby.exceptions.RaiseException
at com.sun.script.jruby.JRubyScriptEngine.evalNode(JRubyScriptEngine.java:456)
[cutting rest as script engine stack trace is irrelevant]
Caused by: org.jruby.exceptions.RaiseException: Test
<unknown>:1: Test (RuntimeError)
...internal jruby stack elided...
...internal jruby stack elided...

Although overriding only getStackTrace() will probably result in getting output closer to what Sun output for Java exceptions.