fix: searching tag refinement was sometimes not working

[bradenmacdonald]

Description

Fixes openedx/modular-learning#224

It turns out that if no documents on the instance contain any "level 3" tags, then the search which tries to filter the tags using a keyword search (and explicitly includes the tags.level3 field) would fail. The fix is simple, to always explicitly add tags.levelX as "searchable fields", rather than assuming they'll be implicitly searchable because the parent tags field is included.

Supporting information

Testing instructions

To reproduce the bug, before checking out this branch, go to this line:

edx-platform/openedx/core/djangoapps/content/search/documents.py

Line 205 in 7f7cade

for level in range(4):

and change 4 to 3. This simulates "no documents have level 3 tags". Then run python manage.py cms reindex_studio --experimental.

Then open the search UI in course authoring and enter a keyword into the tags filter. It should have no effect.

Then checkout this branch, run the reindex command again, and see that the fix worked.

Deadline

We want to get this backported to Redwood ASAP.

Private Ref: MNG-4283

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[rpenido]

LGTM @bradenmacdonald! 👍

• I tested this following the testing instructions
• I read through the code and considered the security, stability and performance implications of the changes.
• I tested that the UI can be used with a keyboard only (tab order, keyboard controls).
• Includes tests for bugfixes and/or features added.

[pomegranited]

👍 This fixes the issue described perfectly, and I've raised another potential issue, see inline comment.

• I tested this on my tutor dev stack using the PR instructions
• I read through the code.
• I checked for accessibility issues N/A
• Includes code docs to explain the change.
• User-facing strings are extracted for translation N/A

[pomegranited]

Hmm.. I thought we only supported a 3-level tag hierarchy, but this PR uses 4 levels, and I can see 4 levels in ESDC..

Do we need to update openedx-learning too?

[bradenmacdonald]

Yeah, I've been a bit inconsistent about that. We only officially support 3 levels, though at the core the code will support a higher number of levels - it's just that some search and listing features only work on three (or in this case 4) levels. It would be a good change in the future to drop this fourth level from the search engine and to prevent the import or creation of taxonomies with 4 levels (or support 4 levels). For now I don't think it's a bug we need to fix though.

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[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.