slideshare/ERROR_HANDLING_STANDARDS.md

# Error Handling Standards

## Current State: INCONSISTENT
Error handling varies across the codebase - some functions have comprehensive error handling while others are missing it entirely.

## Required Error Handling Patterns

### 1. Error Boundaries (MISSING)
Implement React error boundaries for component-level error handling:

```typescript
// ✅ IMPLEMENT - ThemeErrorBoundary.tsx
import React, { Component, ErrorInfo, ReactNode } from 'react';

interface Props {
  children: ReactNode;
  fallback?: ReactNode;
}

interface State {
  hasError: boolean;
  error?: Error;
}

export class ThemeErrorBoundary extends Component<Props, State> {
  constructor(props: Props) {
    super(props);
    this.state = { hasError: false };
  }

  static getDerivedStateFromError(error: Error): State {
    return { hasError: true, error };
  }

  componentDidCatch(error: Error, errorInfo: ErrorInfo) {
    console.error('Theme component error:', error, errorInfo);
    // Log to error reporting service in production
  }

  render() {
    if (this.state.hasError) {
      return this.props.fallback || (
        <div className="error-fallback">
          <h2>Something went wrong</h2>
          <p>There was an error loading the theme system.</p>
          <button onClick={() => window.location.reload()}>
            Reload Page
          </button>
        </div>
      );
    }

    return this.props.children;
  }
}
```

### 2. Async Error Handling (STANDARDIZE)
Consistent pattern for all async operations:

```typescript
// ✅ STANDARD PATTERN
const performAsyncOperation = async (id: string) => {
  try {
    setLoading(true);
    setError(null);
    
    const result = await riskyOperation(id);
    
    if (!result) {
      throw new Error(`Operation failed for ${id}`);
    }
    
    return result;
  } catch (error) {
    const message = error instanceof Error ? error.message : 'Unknown error occurred';
    setError(message);
    console.error(`Async operation failed:`, error);
    throw error; // Re-throw if caller needs to handle
  } finally {
    setLoading(false);
  }
};
```

### 3. Hook Error Handling (IMPLEMENT)
Custom hook for consistent error states:

```typescript
// ✅ IMPLEMENT - useAsyncOperation.ts
import { useState, useCallback } from 'react';

interface AsyncState<T> {
  data: T | null;
  loading: boolean;
  error: string | null;
}

export function useAsyncOperation<T>() {
  const [state, setState] = useState<AsyncState<T>>({
    data: null,
    loading: false,
    error: null
  });

  const execute = useCallback(async (operation: () => Promise<T>) => {
    setState(prev => ({ ...prev, loading: true, error: null }));
    
    try {
      const data = await operation();
      setState({ data, loading: false, error: null });
      return data;
    } catch (error) {
      const message = error instanceof Error ? error.message : 'Operation failed';
      setState(prev => ({ ...prev, loading: false, error: message }));
      throw error;
    }
  }, []);

  return { ...state, execute };
}
```

### 4. Network Error Handling (ENHANCE)
Standardized fetch error handling:

```typescript
// ✅ STANDARD PATTERN
const fetchWithErrorHandling = async (url: string, options?: RequestInit) => {
  try {
    const response = await fetch(url, options);
    
    if (!response.ok) {
      throw new Error(`HTTP ${response.status}: ${response.statusText}`);
    }
    
    return response;
  } catch (error) {
    if (error instanceof TypeError) {
      throw new Error('Network error - check your connection');
    }
    throw error;
  }
};
```

## Error Types & Classifications

### 1. User Errors (Recoverable)
- Invalid theme selection
- Missing form data
- File upload issues
**Handling**: Show user-friendly message, allow retry

### 2. System Errors (Technical)  
- Network failures
- Parse errors
- Configuration issues
**Handling**: Log details, show generic message, provide fallback

### 3. Critical Errors (Unrecoverable)
- Dependency failures
- Memory issues  
- Corrupt data
**Handling**: Error boundary, full page reload option

## Logging Standards

### Development
```typescript
// ✅ PATTERN
console.group(`🔥 ${operation} Error`);
console.error('Details:', error);
console.error('Context:', context);
console.groupEnd();
```

### Production
```typescript
// ✅ PATTERN (when error service added)
errorReportingService.captureException(error, {
  context,
  user: getCurrentUser(),
  timestamp: new Date().toISOString()
});
```

## Error Message Standards

### User-Facing Messages
- **Clear & Actionable**: "Could not load theme. Please try again."
- **No technical jargon**: Avoid error codes, stack traces
- **Suggest solutions**: "Check your connection and retry"

### Developer Messages  
- **Detailed context**: Include operation, parameters, state
- **Stack traces**: Preserve for debugging
- **Structured data**: Consistent error object format

## Implementation Checklist

### HIGH PRIORITY
- [ ] Add ThemeErrorBoundary to App.tsx
- [ ] Implement useAsyncOperation hook
- [ ] Standardize theme loading error handling
- [ ] Add network error handling to fetch operations

### MEDIUM PRIORITY
- [ ] Create error fallback components
- [ ] Add error recovery mechanisms (retry buttons)
- [ ] Implement error state consistency across components
- [ ] Add loading state management standards

### LOW PRIORITY  
- [ ] Add error reporting service integration
- [ ] Implement error analytics tracking
- [ ] Add error rate monitoring
- [ ] Create error handling documentation

## Testing Requirements
- **Error boundary testing**: Verify fallback rendering
- **Async error testing**: Test network failures, timeouts
- **Recovery testing**: Ensure retry mechanisms work
- **Error state testing**: Verify error messages display correctly

## Current Problem Areas

### Missing Error Boundaries
No React error boundaries implemented - component errors crash the app

### Inconsistent Async Patterns
Some async operations handle errors, others don't:
- `themeLoader.ts` ✅ Has good error handling
- Some components ❌ Missing error handling

### No Error Recovery
Users cannot recover from errors - no retry buttons or reload options

### Logging Inconsistency  
Mix of `console.warn`, `console.error`, and no logging