Issue Summary

The Jira UI and the REST API end point /rest/api/2/issue/<issue_key> show conflicting/inconsistent results when the Linked Issues field is set to hidden in the Field Configuration.

Steps to replicate

1. Create a new project (the project will be called "SCRUM" in these steps)
2. Go to ⚙ > Issues > Field Configurations
3. Click on the Config button next to the Field Configuration used by the SCRUM project
4. Search for "Linked Issues", and click on the Hide link next to it
   
5. Create 2 new issues in the SCRUM project
6. From one of these issues (SCRUM-27 in the example illustrated in the screenshot), click on More > Link, and link this issue to the other issue
   
7. Open the URL <JIRA_BASE_URL>/rest/api/2/issue/<issue_key> (for the issue SCRUM-27) in a new browser tab

Observed results

• The Issue Links panel is visible in the Jira UI in the View Issue screen
  
• The REST API does not show the issuelinks field, which is inconsistent with what we see in the View Issue screen:
  

Expected results

The expected results is that what we see in the Jira UI and what we get from the Jira REST API should be consistent:

• either the Issue Links panel should be hidden (since the Linked Issues field is set to hidden), AND the REST API should not show the issuelinks field
• Or the Issue Links panel should be visible, AND the REST API should show the issuelinks field

Other impact of this bug

Another impact of this bug is the fact that Automation Rules (from Automation For Jira) will not be able to "access" the issue links, and as a result, the "Delete Issue Links" action will no do anything.

For more information about this impact, please refer to the KB article Automation For Jira - The "Delete Issue Links" action does not delete any link

Workaround

To avoid any confusion, and to make sure that what the REST API returns is consistent with what is seen in the View Issue screen, configure the Linked Issues field to be "shown" in the Field Configuration:

In such case, the REST API will show the issuelinks field: