Network errors, empty states, and edge cases show user-friendly messages

Reviewers deliberately test on degraded networks and with edge-case data. Empty catch blocks (CWE-390) that swallow errors produce blank white screens — a visible failure that signals low quality and triggers rejection under Apple's guideline 2.1. ISO 25010:2011 fault-tolerance requires systems to continue operating under abnormal conditions. Beyond rejection risk, raw error messages ({error.message}) leak implementation details and destroy user trust. A screen that shows nothing when the network is bad is indistinguishable from a bug.

Implement all four UI states for every data-fetching screen.

// src/screens/FeedScreen.tsx
export default function FeedScreen() {
  const { data, isLoading, error, refetch } = useFeed();

  if (isLoading) return <ActivityIndicator />;
  if (error) return (
    <View style={styles.center}>
      <Text>Couldn't load your feed.</Text>
      <Button title="Try again" onPress={refetch} />
    </View>
  );
  if (!data?.length) return <EmptyState message="Nothing here yet — check back soon." />;
  return <FlatList data={data} renderItem={renderItem} />;
}

Never render {error.message} or {error.toString()} directly. Test every screen with airplane mode enabled on the simulator before submission.

• ID: error-states-handled
• Severity: high
• What to look for: Count all relevant instances and enumerate each. Search for catch blocks that are empty or only call console.log(). Look for screens that fetch data but have no empty-state UI (no results, no content). Check for raw error objects being rendered to the user: {error.message}, {err.toString()}, JSON-stringified objects displayed in the UI. Look for undefined or null rendered where JSX expects a string. Also look for "Something went wrong" text with no actionable retry option. In Flutter, check FutureBuilder and StreamBuilder for missing snapshot.hasError and snapshot.connectionState == ConnectionState.none handling.
• Pass criteria: All data-fetching screens have: a loading state, a non-empty content state, an error state with a user-friendly message and retry option, and an empty state (if the data set can be empty). At least 1 implementation must be verified.
• Fail criteria: Empty catch blocks that swallow errors silently; raw error messages or stack traces visible in the UI; screens that show a blank white area when data fails to load; no retry mechanism after network errors.
• Skip (N/A) when: Never.
• Detail on fail: "ProfileScreen catch block only calls console.log — network errors show a blank screen" or "FeedScreen has no empty-state UI — new users see a completely blank feed with no guidance"
• Remediation: Reviewers test on real networks (sometimes deliberately bad ones) and with edge-case data.
  1. For every data-fetching screen, implement all four states:

     if (isLoading) return <LoadingSpinner />;
     if (error) return <ErrorView message="Couldn't load data" onRetry={refetch} />;
     if (!data?.length) return <EmptyState message="Nothing here yet" />;
     return <DataList data={data} />;
     

  2. Never render {error.message} or {error.toString()} directly — show a friendly message instead
  3. Add a retry button to all error states
  4. Test by disabling network access on the simulator/device and navigating through the app