fix: hide unavailable sequence title in course breadcrumbs [BB-4305]

[Agrendalath]

Description

When a sequence title is unavailable for a user (e.g. before starting a timed exam), the None value is displayed in course breadcrumbs. This hides it in such cases and ensures that a trailing breadcrumb separator is not displayed.

This replaces #27900.

Jira

OSPR-5882

Sandbox

https://pr28028.sandbox.opencraft.hosting/

Note: the course navigation does not work properly in the legacy frontend, but it's an issue related to the master branch. Setting courseware.use_legacy_frontend didn't resolve this, so we've included a direct link to the exam in testing instructions.

Testing instructions

1. Go to this page.
2. Log in as audit.
3. Check that the empty unit name is hidden.

Manual testing instructions

1. Add the following to envs/private.py:

   from .common import FEATURES
   FEATURES['ENABLE_SPECIAL_EXAMS'] = True

2. Go to the LMS shell and run paver compile_sass.
3. Set a subsection as a timed exam in Studio (Subsection -> Advanced -> Timed).
4. Log in as honor (or another non-staff user).
5. Go to the exam in LMS and check that None is no longer visible.

Deadline

None.

Reviewers

• @shimulch
• edX reviewer[s] TBD

Settings

EDXAPP_FEATURES_EXTRA:
  ENABLE_SPECIAL_EXAMS: true

[openedx-webhooks]

Thanks for the pull request, @Agrendalath! I've created OSPR-5882 to keep track of it in JIRA, where we prioritize reviews. Please note that it may take us up to several weeks or months to complete a review and merge your PR.

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[edx-status-bot]

Your PR has finished running tests. There were no failures.

[shimulch]

@Agrendalath Thanks for fixing this. LGTM 👍

• I tested this on my local devstack. Reproduced the issue and verified that this PR resolves it.
• I read through the code
• [N/A] I checked for accessibility issues
• Includes documentation
• [N/A] I made sure any change in configuration variables is reflected in the corresponding client's configuration-secure repository.

[Agrendalath]

@natabene, this is ready for your review.

[natabene]

@Agrendalath Thank you for your contribution.

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@Agrendalath 🎉 Your pull request was merged!

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[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the staging environment in preparation for a release to production.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the production environment.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the staging environment in preparation for a release to production.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the production environment.