Restriction on workflow transition based on sub-task custom field value

[Deleted user]

I am looking to customize JIRA workflow transition based on the value of custom fields associated only with sub-task of that issue, any suggestions please? 

[Bob Swift OSS (Bob Swift Atlassian Apps)]

If it is sufficient to have a validator to do this then I can offer another solution. A condition will not show the transition at all, but with a validator solution, the transition will appear and when attempted can indicate an error message to the user if the custom field is not set correctly. This is good if the user has the opportunity to set the custom field value on the transition screen. If not, it is annoying to the user to see a transition that is not valid .

Conditioned validator from Update on Transition for JIRA is built for regex based comparisons for validation.

[GabrielleJ]

We need a template to combine Nic and Joe's answers! Upvote upvote! 

[Nic Brough -Adaptavist-]

And Bob's

[GabrielleJ]

and Bob's. Update Confluence Question to auto-comment based on relativity.

[Joe Pitt]

Remember, anything you write may not work with the next release. Another option would be to look for a plugin that will set a field in the parent task when something is set in the subtask. Also, keep in mind that there may be multiple subtasks.  Even if that isn't intended, a user may do it so your code needs to be able to handle it or add code to prohibit creating a subtask if one already exists for the issue.

[Nic Brough -Adaptavist-]

You'll need to find or write code to create a condition that can check for sub-tasks and read their fields for the data to base the decision on.