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Validators check that any input available to the transition (such as user-supplied input) is valid before the transition is performed. If a transition's validator 'fails', the transition's post functions will not be executed and the issue will not progress to the destination step of the transition.

You can use Power Scripts Scripts™ for Jira and SIL SIL™ to define a large set of validators beside the default validators offered by Jira, by just adding a (k) SIL SIL™ Validator to a transition and publishing the workflow, as described here.

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string errorMsg = "You must enter a comment!";
if(!hasInput("comment")) {
   return false, "comment", errorMsg;
}

Field has single value

A SIL SIL™ validator for checking if a multi-valued field does not contain more than one value during a transition:

string errorMsg = "You must choose a single fix version!";
if(size(fixVersions) > 1) {
   return false, "fixVersions", errorMsg;
}

Parent status

A SIL SIL™ validator which ensures that the current issue's parent issue is in one of the specified Statuses:

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Validation based on regular expression

A SIL SIL™ validator which checks if a text field matches a regular expression (eg for a social number):

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Force a custom field to be required if another field was set to a certain value

A SIL SIL™ validator which makes custom field Product with id customfield_10200 required in the resolve screen only if the resolution was set to Fixed:

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Ensure that the issue has at least one attachment

A SIL SIL™ validator which checks if an issue has any file attached during a transaction:

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Validation based on mathematical expression

A SIL SIL™ validator which checks if a numeric custom field is greater than or equal to 0:

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Validation based on date-time expression

A SIL SIL™ validator which checks if due date is before current date:

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Compare two parsed texts

A SIL SIL™ validator which checks if description contains summary:

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Users in a field are/aren't in a project role

A SIL SIL™ validator which checks if users selected in a multi user picker custom field are in a given project role:

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A custom field is/isn't initialized

A SIL SIL™ validator which checks if a custom field is initialized during transaction:

string errorMsg = "Field was not initialized!"; 
if(!hasInput("customfield_10500")) { 
   return false, "customfield_10500", errorMsg; 
}

Check user property

A SIL SIL™ validator which checks if a user property has a certain value:

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