Fix: Remove global leaderboard tags when post is not eligible

[lsabor]

The update_global_leaderboard_tags function now removes any existing global leaderboard tags before returning early when a post has no eligible projects with NORMAL visibility.

Fixes #4121

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Summary by CodeRabbit

• Bug Fixes
  • Leaderboard tags are now properly removed from posts when they're no longer applicable.

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📝 Walkthrough

Walkthrough

Modified the update_global_leaderboard_tags function to remove existing leaderboard tags from posts when no eligible normal-visibility projects are found, instead of returning without cleanup.

Changes

Cohort / File(s)	Summary
Leaderboard Tag Cleanup posts/services/common.py	Added logic to filter out and remove LEADERBOARD_TAG-type projects from posts when no eligible normal-visibility projects exist, ensuring stale leaderboard tags are properly cleaned up

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

🐰 Tags that linger with no worthy place,
Are swept away with grace,
When leaderboards don't qualify,
The cleanup makes things fly,
A tidy post, a rabbit's delight! ✨

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: removing global leaderboard tags when a post is ineligible.
Linked Issues check	✅ Passed	The code changes directly implement the requirement from issue #4121 to remove existing global leaderboard tags when posts are ineligible.
Out of Scope Changes check	✅ Passed	All changes are scoped to the update_global_leaderboard_tags function and directly address the requirement to remove ineligible leaderboard tags.

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✨ Finishing touches

• 📝 Generate docstrings

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📜 Recent review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 7f1d6a1 and a7dd76d.

📒 Files selected for processing (1)

• posts/services/common.py

🧰 Additional context used

🧠 Learnings (1)

📚 Learning: 2026-01-15T19:29:58.940Z

Learnt from: hlbmtc
Repo: Metaculus/metaculus PR: 4075
File: authentication/urls.py:24-26
Timestamp: 2026-01-15T19:29:58.940Z
Learning: In this codebase, DRF is configured to use IsAuthenticated as the default in REST_FRAMEWORK['DEFAULT_PERMISSION_CLASSES'] within metaculus_web/settings.py. Therefore, explicit permission_classes([IsAuthenticated]) decorators are unnecessary on DRF views unless a view needs to override the default. When reviewing Python files, verify that views relying on the default are not redundantly decorated, and flag cases where permissions are being over-specified or when a non-default permission is explicitly required.

Applied to files:

• posts/services/common.py

🧬 Code graph analysis (1)

posts/services/common.py (2)

front_end/src/types/projects.ts (1)

• Project (10-16)

projects/models.py (2)

• Project (212-495)
• ProjectTypes (213-223)

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🔇 Additional comments (1)

posts/services/common.py (1)

67-81: LGTM! Correctly removes leaderboard tags when post is no longer eligible.

The implementation properly addresses the issue by removing existing LEADERBOARD_TAG projects before the early return. The approach is consistent with the pattern used later in the function (lines 110-114) and safely handles edge cases (no existing tags, empty projects).

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