fix: stop the course outline scrolling back while you work in it

[ihor-romaniuk]

Description

Open a course outline through a link that points at one of its blocks — the kind Studio search and "view in outline" produce, with ?show=<block> in the address — and the page starts snapping back to that block. Opening the menu on any section is enough to be thrown back to it, which makes the outline hard to work in at all. The block stays highlighted for as long as the link is in the address bar, and the outline reads that as "scroll to it" every time it re-renders.

The outline now scrolls to the highlighted block when you arrive and then leaves the page alone.

Implementation notes

• createGlobalState in src/data/apiHooks.ts returned setData and resetData as plain functions declared in the hook body, so both got a new identity on every render.
• SectionCard, SubsectionCard and UnitCard list resetScrollState among the dependencies of the effect that calls scrollToElement, so that effect ran on every render. While ?show= names the card, its guard isScrolledToElement stays true, so every render scrolled. The effect also calls resetScrollState(), which invalidates the query and causes another render — hence repeated jumps rather than one.
• The fix is in the hook rather than in the three cards: a hook whose callbacks are read as dependencies has to keep their identity, the way useQuery's refetch does. queryKey is memoised on queryKeyArgs so the callbacks can depend on it honestly, without a ref.
• Fixing the three dependency arrays instead would also work, but it leaves the same trap in place for every other caller of createGlobalState.

Screenshot/Video

Before

before.mov

After

after.mov

Testing

Preconditions: a course with several sections, a staff user.

1. Open the course outline with a block in the address, for example <AUTHORING>/course/<courseId>?show=<sectionId>.
2. Expected: the page scrolls to that section and highlights it — unchanged.
3. Scroll away from the highlighted section.
4. Open the menu on any other section.
5. Expected: the menu opens and the page stays where you left it. Before this change it scrolled back to the highlighted section.
6. Rename a section, then open and close a few menus.
7. Expected: the page stays put throughout.
8. Open the outline without ?show= and repeat.
9. Expected: unchanged.

Verified locally

Check	Result
Outline with ?show=<section>, scrolled to 6000px, section menu opened	page stays at 6000px; before the fix it scrolled to 3654px, a jump of 2346px
Arrival behaviour	still scrolls to the block and highlights it — one highlighted card, page settles at its top
Section menu	opens as before: aria-expanded flips and the dropdown renders
jest src/course-outline	32 suites, 357 tests
jest src/data/apiHooks.test.tsx	5 tests, including two new ones for the hook
Red/green	restoring the plain functions fails the new identity test
tsc, dprint, oxlint	clean
Not verified	One browser at 1440×863. The three card effects were left as they are, so the fix rests on the hook keeping its callbacks stable.

[openedx-webhooks]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.03%. Comparing base (16e19f1) to head (980c8ab).
⚠️ Report is 16 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3213      +/-   ##
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+ Coverage   95.92%   96.03%   +0.10%     
==========================================
  Files        1397     1407      +10     
  Lines       33581    34288     +707     
  Branches     7947     7882      -65     
==========================================
+ Hits        32214    32929     +715     
- Misses       1308     1318      +10     
+ Partials       59       41      -18     

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[bradenmacdonald]

I believe this has already been fixed on master. I just tested it now and could not reproduce the issue.

SectionCard, SubsectionCard and UnitCard list resetScrollState among the dependencies of the effect that calls scrollToElement.

I don't think this is correct, because SectionCard, SubsectionCard and UnitCard were removed in #3073 (replaced them with OutlineNode).

Nevertheless, it may still be worth merging this PR. The useCallback/useMemo on setData/resetData/queryKey stops the outline effect from re-running on every render, and removes a footgun for future callers.

However, I'm wondering why we even have createGlobalState at all - it's a bit of a hack to share state among components using React Query, but it's not using any of the query lifecycle or fetching features (staleness, refetching, invalidation). It would be cleaner to use a small context or perhaps useSyncExternalStore.

@navinkarkera what do you think? could you please review this?

[navinkarkera]

Even I was not able to reproduce the issue.

But I agree with @bradenmacdonald , it is still worth merging.

However, I'm wondering why we even have createGlobalState at all - it's a bit of a hack to share state among components using React Query, but it's not using any of the query lifecycle or fetching features (staleness, refetching, invalidation). It would be cleaner to use a small context or perhaps useSyncExternalStore.

Yes, I added it while refactoring outline page and simplifying storage, it felt cleaner to have react query manage the state but I agree that it would be better to use a context (don't remember why I did not do it).

[bradenmacdonald]

@ihor-romaniuk Can you please just make this change to the comment here, and then I'll merge this fix?

--- a/src/data/apiHooks.ts
+++ b/src/data/apiHooks.ts
@@ -152,7 +152,12 @@ export const useCourseDetails = (courseId: string) => {
 };
 
 /**
- * Create a global state function for a query.
+ * Create a global state function.
+ *
+ * This is sort of a hack for sharing state between components using React Query
+ * without actually loading data from an API. Instead of using this, please use
+ * a small context or `useSyncExternalStore`, and feel free to remove this once
+ * we've replaced the existing usage of it on the outline page.
  */
 export function createGlobalState<T>(
   queryKeyFn: (queryKeyArgs?: any) => QueryKey,

[ihor-romaniuk]

@bradenmacdonald Thanks for your review and JSDOC was updated.