Add convenience prop to JsonInput to fire when error state changes

[kb-ig]

The JsonInput component has a handy feature where it displays an error state (and optionally a custom error message) if the input JSON is invalid.

I think it would be useful to add a prop to this component (e.g. onHasErrorChanged) which fires when the validation status changes from valid to invalid or vice versa.

My use case is that I want to have a button that's clicked to process the JSON in some way, however I want to disable this button when the JSON is invalid.

The only alternative solution I can find is to use the onChange function to:

• capture the JSON value (which I'm doing anyway)
• Use a try/catch to JSON.parse the JSON value, setting a separate hasError state accordingly

This work around is fine, but I think a convenience prop would be useful.