Issue Summary

When using the Rest API endpoint https://YOUR_INSTANCE.atlassian.net/rest/api/3/issuetype, all issue types with the scope information are used on Next-Gen projects, for example:

self: "https://YOUR_INSTANCE.atlassian.net/rest/api/3/issuetype/10156",
id: "10156",
description: "",
iconUrl: "https://YOUR_INSTANCE.atlassian.net/secure/viewavatar?size=medium&avatarId=10321&avatarType=issuetype",
name: "IssueTypeTest",
untranslatedName: "IssueTypeTest",
subtask: false,
avatarId: 10321,
scope: {
  type: "PROJECT",
  project: {
    id: "10144"
  }
}

Once you move that Next-gen project to the trash, all issue types from that project are shown without the scope under them. This creates bias information, where the customer could get duplicated issue type names without knowing which one is from Classic projects.

Steps to Reproduce

1. Create a Classic Issue type (example: IssueTypeTest)
2. Create an Issue type with the same name on a Next-gen project
3. Run the Rest API call to see the difference between them (the scope value): https://YOUR_INSTANCE.atlassian.net/rest/api/3/issuetype
4. Move this Next-gen project to the trash
5. Run the endpoint for step 3 again.

There is no direct way of knowing what is the Classic field

Expected Results

You can't fetch Issue types from Next-gen project that are on the trash.

Actual Results

You fetch Issue types that seem to be from Classic, but they aren't foundable on the UI.

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available