Steps to Reproduce

produce an error during widget initialization (usually happens accidentally)

jserror.Awidget = zk.$extends(zul.wgt.Span, {
    $define: {
        prop1: _myFunc = function() {
            console.log("something");
        },
        prop2: _myFunc,
        prop3: myFunc /* forgot '_' */
    }
}, {});

Current Result

the console error shows a misleading error message, omitting the real cause

Expected Result

also show the root cause why the widget is "Unknown"
especially the line number where the error happens

e.g. log or rethrow the error

catch(error) {
   console.error(error);
}

or

catch(error) {
   throw error;
}

also consider failing the package load operation by not calling setLoaded and report a meaningful error message instead
e.g.

"failed to load 'mypackage.wpd' check browser console for error details"

Debug Information

as of now there's a try without a catch block swallowing the error

Workaround

enable stop on uncaught exceptions in dev tools (hard to know when the error indicates nothing)