Problem Definition

Jira has the validator "field required on transition", which means the field needs a value added during the transition but does not have a validator to check if a field has or not a valid value on it before the transition.

Suggested Solution

Create a validator that will check if a field has a valid value before allowing the transition to complete, possibly using the operators >,<,=,!=

Workaround

The current workaround is to set a Condition for the transition, but this is a terrible UX since users will have no idea why the button is missing.