Sehoon Shon
1.7 KiB
Common Regression Patterns
When analyzing a "bad" commit, look for these common patterns that often cause regressions in this codebase.
1. State Synchronization Issues
Symptoms: UI doesn't update, stale data, "disappearing" history.
Pattern: State is derived from multiple sources that are updated at
different times, or state is updated via side-effects (e.g., useEffect or
callbacks) instead of being purely derived. Fix: Use useMemo to derive
state or ensure atomic updates.
2. Missing Hook Dependencies
Symptoms: Logic runs with old state, variables seem stuck. Pattern: A
useCallback, useMemo, or useEffect has an incomplete dependency array.
Check: Look for ESLint suppression comments like
// eslint-disable-next-line react-hooks/exhaustive-deps.
3. Bypassed Logic
Symptoms: Feature works sometimes but fails in specific paths (e.g., after
cancellation). Pattern: A refactor introduced a new submission or update
path that bypasses existing validation or cleanup logic. Check: Search for
direct calls to onSubmit or setState that should have gone through a wrapper
function (like handleSubmit).
4. Environment/Platform Specifics
Symptoms: Works on MacOS but fails on Windows or Linux. Pattern: Usage
of path delimiters (/ vs
``), terminal escape sequences, or platform-specific CLI flags. Fix: Use node:path
and verify terminal capability detection.
5. Mock Mismatch in Tests
Symptoms: Tests pass but application fails (or vice versa). Pattern: A mock in a unit test was not updated to reflect a change in the real implementation's interface or behavioral expectations. Check: Verify that mock return values and implementations match the current code.