Java Lab2: fix reset bug

[molly-moen]

I found that on Java Lab levels with mini apps, the code was getting reset to the initially loaded sources on run. This was because the labConfig was getting re-created and passed to useSource, which is doing a reference equality check to determine if the initial sources had changed. This PR memoizes the labConfig to avoid sending a different object. At first I also updated the reference check to an equality check, but I think it could cause a regression in the teacher viewing student code case. In that case, if the student's code was the same as the teacher's initial sources, and the teacher had made a change, the student's code would not load. Therefore we need to keep the reference equality check.

Before

Neighborhood (bug present)

Screen.Recording.2026-06-17.at.3.26.11.PM.mov

Console (bug not present)

Screen.Recording.2026-06-17.at.3.26.38.PM.mov

After

Neighborhood (fixed)

Screen.Recording.2026-06-17.at.3.27.18.PM.mov

Console (bug still not present)

Screen.Recording.2026-06-17.at.3.27.49.PM.mov

Testing story

Tested locally

[Copilot]

Pull request overview

Fixes a Java Lab (Lab2) regression where running a mini-app level could reset the editor to the initially loaded server sources due to referential changes in labConfig / initialSources. The fix stabilizes derived config objects and ensures useSource detects meaningful initialSources changes by value rather than reference.

Changes:

• Update useSource to compare initialSources via deep equality instead of reference equality to avoid unintended resets.
• Memoize/stabilize derived Java Lab labConfig so downstream initialSourcesWithLabConfig doesn’t churn on deep-equal inputs.
• Add a unit test guarding against resets when initialSources changes by reference but not by value.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
apps/test/unit/codebridge/hooks/useSourceTest.tsx	Adds coverage to ensure deep-equal initialSources does not trigger a reset.
apps/src/javalab/lab2/Javalab2View.tsx	Stabilizes derived labConfig to prevent unnecessary initialSourcesWithLabConfig object churn.
apps/src/codebridge/hooks/useSource.ts	Switches reset detection from reference equality to deep equality for initialSources.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[fisher-alice]

Nice - appreciate that you included why you stuck with the reference quality check in description (e.g., teacher viewing code case) - makes sense!