Indicate JSON errors in the input data

[christian-konrad]

Is your feature request related to a problem? Please describe.

When the form mock input data is invalid, the form rendering stops, but there is no indicator of that error. Users might think the error is in the form, rather than in the input json.

Describe the solution you'd like

We should indicate it in the problems panel, as well as highlight the error in the json panel.

Describe alternatives you've considered

Show an error in the form preview itself, since users may spend their attention into this window. But this may result in too much flickering of the preview window.

Additional context

Add any other context or screenshots about the feature request here.

[pinussilvestrus]

One simple thing we can do is use the linting capabilities of the lang-json CodeMirror package.

We should indicate it in the problems panel

That's anyway something that would need to be fixed in the Desktop Modeler directly. What can help here is to fire an event once a parsing error happens.

formPlayground.on('formPlayground.inputDataError', function(error) {
  // do stuff, e.g. display in problems panel
});

[pinussilvestrus]

I sketched that via bpmn-io/form-js#386