Apply Optimistic UI Updates with Rollback
Update the UI immediately, send the request, and roll back on error so the interaction feels instant and stays correct.
Task
Add const prev = items; setItems([...items, newItem]); try { await api.add(newItem); } catch { setItems(prev); } so the interface remains usable and accessible under the edge cases that manual testing skips.
When to use this
A screen reader user reports the page is unusable because const prev = items; setItems([...items, newItem]); try { await api.add(newItem); } catch { setItems(prev); } was never implemented, flagged in a support ticket.
Prerequisites
- A frontend component or page in the codebase
- A build with the relevant framework configured
Steps
1. Configure const prev = items; setItems([...items, newItem]); try { await api.add(newItem); } catch { setItems(prev); } in the project configuration file with the recommended defaults.
const prev = items; setItems([...items, newItem]); try { await api.add(newItem); } catch { setItems(prev); }
Expected output: The configuration is accepted and const prev = items; setItems([...items, newItem]); try { await api.add(newItem); } catch { setItems(prev); } runs without errors on the first invocation.
2. Run the check locally to verify const prev = items; setItems([...items, newItem]); try { await api.add(newItem); } catch { setItems(prev); } produces the expected result before pushing.
pnpm test
Expected output: Local run matches CI behavior; no surprises after push.
3. Add the gate to the CI pipeline so const prev = items; setItems([...items, newItem]); try { await api.add(newItem); } catch { setItems(prev); } blocks merge on failure.
- name: Run add optimistic ui update
run: pnpm test
Expected output: Pull requests with failing const prev = items; setItems([...items, newItem]); try { await api.add(newItem); } catch { setItems(prev); } are blocked from merging.
Troubleshooting
Problem
The check passes locally but fails in CI
Solution
Pin dependency versions and the runtime to match CI exactly; reproduce with the same Docker image or act.
Problem
Configuration is rejected with a schema error
Solution
Check the tool version matches the config schema; older versions may not support newer fields.
Limitations
- The gate only runs on events that trigger the workflow; locally pushed commits bypass it.
- Configuration drift is possible if someone edits settings outside version control.
Handle the edge case
Start by measuring the problem. Update the UI immediately, send the request, and roll back on error so the interaction feels instant and stays correct. The most common mistake is adding the gate without first confirming it catches the issue you care about. Run const prev = items; setItems([…items, newItem]); try { await api.add(newItem); } catch { setItems(prev); } against the current codebase and inspect the output before wiring it into CI.
const prev = items; setItems([...items, newItem]); try { await api.add(newItem); } catch { setItems(prev); }Test with real tools
Once the gate is in place, make failures actionable. A failing const prev = items; setItems([…items, newItem]); try { await api.add(newItem); } catch { setItems(prev); } should point to the exact file and line, not a generic error. Pin the tool version in the lockfile so a upstream release does not silently change behavior. Review the gate output in every pull request just like a test result.