Differnce between condition and validation
In a slightly simpler terms, conditions are evaluated even before the issue is shown to the user to decide if a workflow transition is valid for the user.
Validations happens once the workflow transition is triggered when the user submits on the workflow screen.
With the conditions, the button does not appear until they are met. With validators in the past if the field was required but is blank or something then a red asterisk appears next to the field which gives the user more feedback than the button not appearing. If the field is not visible on the screen then what feedback is provided to the user? Anything useful?
We are running JIRA server v7.7.0. A hybrid could also be used for validators of some things then conditions of others to hide the button until it is at least close to ready. If more feedback is provided then I would be inclined to use validators more than hide the button so that the user is provided feedback. Would at least help in troubleshooting advanced workflow checks when the user can't do something they want rather than them just saying they don't have the button. The permission helper also isn't helpful with advanced workflow options when there are more options than just permissions.
We have moved to using validators for exactly for this purpose - to provide a custom error message as hiding the button (or more recently hiding the drop down transition in the new view) doesn't guide the user as to what the problem is and how to remedy it.
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