Forums V2 with retired user results in a display error when viewing posts

[blarghmatey]

After migrating courses to the Forums V2 backend, both when using the MongoDB and MySQL backends, if the course has a learner account that has been retired then the discussion MFE is unable to render posts. When clicking on any post in the course it yields a console error of:

Error: Missing ":learnerUsername" param
    s history.ts:494
    E utils.ts:829
    E utils.ts:815
    v AuthorLabel.jsx:108
    React 7
        pi
        wc
        gu
        hu
        pu
        nu
        tu
    O scheduler.production.min.js:13
    T scheduler.production.min.js:14
    <anonymous> task.js:61
    P task.js:35
    j task.js:46
react-dom.production.min.js:188:120

The relevant block appears to be in AuthorLabel.jsx with the code block:

  const learnerPostsLink = (
    <Link
      data-testid="learner-posts-link"
      id="learner-posts-link"
      to={generatePath(Routes.LEARNERS.POSTS, { learnerUsername: author, courseId })}
      className="text-decoration-none text-reset"
      style={{ width: 'fit-content' }}
    >
      {!alert && authorName}
    </Link>
  );

[taimoor-ahmed-1]

@blarghmatey I have opened a PR in forum (openedx/forum#236). Would you be able to test this on your end before I merge it?

[taimoor-ahmed-1]

I wasn't able to reproduce the error on my local setup. These are the steps that I tried:

• Add posts/comments from a learner account
• retire that user from the account page
• Migrate course from mongo to mysql using the management command
• Test whether all posts were showing from a different user account.
• All posts were showing up

@blarghmatey is there something I missed in this testing process?

[blarghmatey]

I am still experiencing this bug when I enable the MySQL backend for a course. The error message I get in the console is:

Error: Missing ":learnerUsername" param
    s history.ts:494
    E utils.ts:829
    E utils.ts:815
    v AuthorLabel.jsx:108
    React 7
    O scheduler.production.min.js:13
    T scheduler.production.min.js:14
    <anonymous> task.js:61
    P task.js:35
    j task.js:46
    6616 task.js:84
    Webpack 12
react-dom.production.min.js:188:120
    React 9
    O scheduler.production.min.js:13
    T scheduler.production.min.js:14
    <anonymous> task.js:61
    P task.js:35
    j task.js:46
    (Async: EventHandlerNonNull)
    6616 task.js:84
    Webpack 12

This is when running the latest build of the discussions MFE from master (231c15a) and the latest build of edx-platform (openedx/edx-platform@604a87c)

I ran the forum_migrate_course_from_mongodb_to_mysql management command for the course I am testing with and immediately started seeing the behavior when the MySQL backend was toggled on. As soon as I toggle off the MySQL backend and go back to Mongo the post will load again.

I'm happy to have a zoom call to look at the production data in the MySQL backend to determine where this bug is originating.