Singleton Issue

[he_art_less]

Hello

I want to create an issue of a special type (let's say "project description") and to be sure, that there can't be any other issues of this type in a project. 

Is it possible?

[Nic Brough -Adaptavist-]

You will need a little bit of code to do it. 

You can create a validator on the "create issue" transition that can search for "project = current project and issuetype = project-description" and if the size of that is larger than zero, fail validation.

[he_art_less]

Thank you, Nic.
Would you mind pointing me an article how to create validators?
What's that, exactly, a plugin?