TypeError: Cannot convert undefined or null to object
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Assessment
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Newbie friendliness
- 72/100
- Issue type
- Bug
- Clarity
- Mostly clear
- Activity status
- Active
- Tech stack
- react, typescript
- Domain
- frontend
Research direction
Start at app/javascript/components/track/exercise-community-solutions-list/exercise-tag-filter/ExerciseTagFilter.tsx:11 and inspect the value passed to Object.keys. Reproduce the exercism-js community-solutions view that triggers the Sentry error, then verify the component no longer throws when that value is undefined or null.
Written by the indexing model from the issue text.
Description
Error
Cannot convert undefined or null to object
Stack trace
../app/javascript/components/track/exercise-community-solutions-list/exercise-tag-filter/ExerciseTagFilter.tsx:11 in ExerciseTagFilter
div
div
div
../app/javascript/components/track/ExerciseCommunitySolutionsList.tsx:44 in ExerciseCommunitySolutionsList
Suspense
../node_modules/@sentry/react/src/errorboundary.tsx:101 in new ErrorBoundary
../node_modules/@tanstack/react-query/src/QueryClientProvider.tsx:30 in QueryClientProvider
Tracking Details
- Project: exercism-js
- Sentry: TypeError: Cannot convert undefined or null to object
- Culprit: Object.keys()
- First seen: Aug 20, 2026
- Dominant language
- Ruby
- Stars
- 547
- Forks
- 168
- Avg merge
- 1d 1h
- Merged PRs (30d)
- 17
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
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