On-change Rules

When building an on-change rule in the workflow constructor, you define the initial criteria for updating issues in the Prerequisites section, then specify which updates to apply in the Actions section.

Here's a workflow rule that automatically assigns purchase requests to the person who is responsible for their review and sets the due date to two weeks in the future.

This sample on-change rule behaves in the following way:

This rule performs the following actions when a change is applied to an issue:

• YouTrack checks for a change to the value in the Subsystem field.

• If the value in the Subsystem changes, the issue is automatically assigned to the owner of the subsystem.

const entities = require('@jetbrains/youtrack-scripting-api/entities');
const workflow = require('@jetbrains/youtrack-scripting-api/workflow');

exports.rule = entities.Issue.onChange({
  title: 'Set subsystem owner as assignee for unassigned issues',
  guard: (ctx) => {
    return !ctx.issue.fields.Assignee && ctx.issue.fields.Subsystem;
  },
  action: (ctx) => {
    const issue = ctx.issue;
    const fs = issue.fields;
    if ((issue.isReported && (fs.isChanged(ctx.Subsystem) || issue.isChanged('project'))) || issue.becomesReported) {
      if (fs.Subsystem.owner) {
        if (ctx.Assignee.values.has(fs.Subsystem.owner))
          fs.Assignee = fs.Subsystem.owner;
        else
          workflow.message(workflow.i18n(
              "{0} is set as the owner of the {1} subsystem but isn't included in the list of assignees for issues in this project. " +
              "The workflow that automatically assigns issues to the subsystem owner cannot apply this change.",
              fs.Subsystem.owner.fullName, fs.Subsystem.name));
      }
    }
  },
  requirements: {
    Assignee: {
      type: entities.User.fieldType
    },
    Subsystem: {
      type: entities.OwnedField.fieldType
    }
  }
});

The components that define this on-change rule are as follows:

• All scripts start with a list of require statements. In this rule, we declare a local variable entities and reference the entities module in the workflow API. This means that everything that is contained in this module can be accessed in this script with the entities variable.

• Each script exports one rule to the exports.rule property. The rule is declared with the Issue.onChange method, which exports the script that follows the declaration as an on-change rule.

• The body of the rule itself contains three properties, as follows:

  Property	Description
  title	An optional human-readable title. The title is only visible in the administrative interface.
  guard	A function that determines the conditions for executing the rule. If the guard condition is not met, the action specified in the rule is not applied to an issue.
  action	The actions that should be applied to each issue. The action is declared as a function that accepts a context as an argument. In this example, we check to see if the Subsystem field was set to a non-null value that has a non-null owner. If so, the rule sets the value of the Assignee field.
  runOn	Determines which issue events trigger the on-change rule. When not specified, rules are triggered on issue update. This property is extended with the following parameters: change — when true, the rule is triggered on issue change. removal — when true, the rule is triggered when an issue is deleted. As the rule in this example is triggered when updates are applied, we don't need to specify values for this property.
  requirements	The list of entities that are required for the rule to execute without errors. This property ensures that rules can be attached to projects safely. In this example, the requirements ensure that both the Subsystem and Assignee fields store the correct types and are available in the project to which the rule is attached. If either field is absent, an error is shown in the Workflows list. The rule cannot be enabled until the required fields are attached.

For a sample of an on-change rule for articles, see the API reference in the Developer Portal.

To learn more about writing workflows in JavaScript, please check out the documentation in our Developer Portal.