fix: release Biorender semaphore permit on invalid email

[rlorenzo]

Summary

BiorenderStudentLookup.GetBiorenderStudentInfo acquires a semaphore permit via throttler.WaitAsync() before checking IsValidEmail, but Release() only runs inside the scheduled Task.Run. Each invalid email permanently consumes a permit, so 20 invalid entries in a row deadlock the loop at WaitAsync() waiting for permits that will never be returned.

Fix

Reorder: trim and validate first, continue on invalid, then WaitAsync only when work is actually being scheduled.

Context

Split from #192 (CodeQL dispose hygiene). CodeRabbit surfaced this during the #192 review, but it is a control-flow correction rather than a dispose annotation, so it lives here for cleaner git log/bisect.

Independent of #192 — either can merge first. Touches adjacent lines on var throttler = new SemaphoreSlim(...) so a trivial merge resolution may be needed for whichever lands second (keep the using from #192, keep the reorder from here).

Test plan

• npm run test:backend — 1946 tests passing
• npm run lint web/Areas/Computing/Services/BiorenderStudentLookup.cs — clean
• npm run verify:build — clean
• Manual: call GetBiorenderStudentInfo with >20 invalid emails, confirm it returns (currently hangs)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 43.02%. Comparing base (d28d37c) to head (f67f12c).

Files with missing lines	Patch %	Lines
...Areas/Computing/Services/BiorenderStudentLookup.cs	0.00%	16 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #209   +/-   ##
=======================================
  Coverage   43.02%   43.02%           
=======================================
  Files         881      881           
  Lines       51437    51437           
  Branches     4812     4812           
=======================================
  Hits        22131    22131           
  Misses      28780    28780           
  Partials      526      526           

Flag	Coverage Δ
backend	43.10% <0.00%> (ø)
frontend	41.47% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[codecov-commenter]

Bundle Report

Bundle size has no change ✅

[rlorenzo]

@coderabbitai review

[coderabbitai]

✅ Actions performed

Review triggered.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: fc518d2b-d1c4-4dd3-91e4-45531c6faa68

📥 Commits

Reviewing files that changed from the base of the PR and between d28d37c and f67f12c.

📒 Files selected for processing (1)

• web/Areas/Computing/Services/BiorenderStudentLookup.cs

---

📝 Walkthrough

Walkthrough

GetBiorenderStudentInfo refactors its email processing loop to validate and normalize emails before acquiring semaphore permits. Invalid addresses are skipped early via continue, preventing wasted resource allocation on malformed input.

Changes

Email Validation and Semaphore Optimization

Layer / File(s)	Summary
Email normalization and semaphore acquisition reordering web/Areas/Computing/Services/BiorenderStudentLookup.cs	Each email is trimmed and appended with @ucdavis.edu when missing an @. Invalid emails skip processing entirely via continue before semaphore acquisition. Valid emails acquire the semaphore, execute Task.Run to fetch student data via GetSingleStudent, and release the permit in a finally block, ensuring resource cleanup.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main fix: reordering semaphore logic to release permits on invalid emails instead of leaking them.
Description check	✅ Passed	The description is well-related to the changeset, explaining the bug (semaphore permit leak on invalid emails), the fix (reorder validation before WaitAsync), and test results.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/biorender-semaphore-leak

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}