@mention results differ between issue creation and issue view

Issue Summary

@mention user in issue description field returns different results between issue creation and issue view.

Steps to Reproduce

1. Create more than 10 users (with username starts with "A") in Jira associated with the same domain e.g: '@mail.uk' email address and another few additional users have 'uk%' in their username/full name.
2. Create an issue in Project A and attempt to @mention user by typing in '@uk' in the issue description field. Check the result of the @mention search list.
3. Navigate to the created issue and @mention user by typing in '@uk' in the issue description field. Check the result of the @mention search list.

Expected Results

The @mention search results should be the same.

Actual Results

The @mention search results differs.

• Two different endpoints are used in issue creation and issue view.
  • The @mention in Jira issue creation screen is calling the following REST endpoint:

    <JIRA_BASEURL>/rest/api/2/user/viewissue/search?projectKey=ABC&maxResults=10&username=uk

• • The @mention in existing issue screen (issue description or issue comment) is calling the following REST endpoint:

    <JIRA_BASEURL>/rest/internal/2/user/mention/search?issueKey=ABC-312&projectKey=ABC&maxResults=10&query=uk

• Both endpoints has the max results of 10 (first 10 results sorted by alphabetical order based on the username) but they both have different search criteria:
  • Issue creation: Jira searches the keyword against user's full name, username or email and returns the first 10 users that has username starting with "A". The search continues to match the keyword (uk) against the first 10 users' full name or username and no match is found. Hence, no result is returned in this use case.
  • Issue view: Jira prioritises the search of users that are involved with the issue (assignee, reporter, watchers, commenters etc). If we failed to find 10 users with the last search, the search continues to match the keyword against user's full name or username.

Workaround

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