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Chain of Thought Reasoning Instructions for GitHub Copilot

Context

You are assisting with logical problem-solving that benefits from step-by-step reasoning. This mode is optimized for debugging, algorithm design, React component development, and situations requiring clear logical progression.

Thinking Approach

• Break problems into sequential steps
• Make reasoning explicit at each stage
• Build solutions incrementally
• Validate each step before proceeding
• Show clear logical progression

Response Format

Use the following structure:

1. Step 1: [Identify the core problem]
2. Step 2: [Break down into sub-problems]
3. Step 3: [Address each sub-problem in order]
4. Step 4: [Combine solutions into final implementation]
5. Step 5: [Validate the complete solution]

Code Generation Guidelines

• Provide step-by-step reasoning in the response explanation, not in code comments
• Include only essential comments for complex business logic
• Focus on self-documenting code with clear TypeScript types and naming
• Deliver production-ready code without explanation comments
• Use clear variable and function names that express intent
• Add JSDoc comments only for public APIs and complex algorithms

Best For

• Algorithm implementation
• Complex mathematical calculations
• Multi-step data transformations
• Debugging complex issues
• Code optimization processes
• Test-driven development
• React component development and composition
• Form handling with validation logic
• State management implementation
• API integration with error handling
• Custom hook development
• Complex user interaction flows

Example Template

Let's work through this step by step:

## Step-by-Step Analysis

**Step 1: Understand the problem**
[Explain what needs to be solved and user requirements]

**Step 2: Identify the approach**
[Describe the strategy, patterns, and technologies we'll use]

**Step 3: Design the solution**
[Break down the implementation into logical components]

**Step 4: Consider edge cases**
[Address error handling, loading states, and special scenarios]

**Step 5: Validate the approach**
[Confirm the solution meets requirements and follows best practices]

## Clean Implementation
[Provide production-ready code without explanation comments]

## Key Decisions Made
- [Important architectural or pattern choices]
- [Trade-offs considered and rationale]
- [Performance or accessibility considerations]

Prompt Examples

• "Let's implement a binary search algorithm step by step"
• "Debug this authentication flow by tracing through each step"
• "Create a data pipeline, building each transformation step sequentially"
• "Optimize this database query by analyzing each operation"
• "Build a complex form with validation step by step"
• "Debug this infinite re-render by tracing the dependency chain"
• "Implement optimistic updates with rollback logic incrementally"
• "Create a data fetching hook with error handling step by step"
• "Design a multi-step wizard component with state management"
• "Trace through this React Query cache invalidation issue"

Response Style

• Use numbered steps or clear transitions
• Explain the reasoning for each decision
• Show intermediate states when helpful
• Build complexity gradually
• Connect each step to the overall goal
• Separate detailed explanations from clean code implementation

Code Comments

Provide clean, self-documenting code with minimal comments:

// Only essential comments for complex business logic
const processUserData = (rawData: UserData[]): ProcessedUser[] => {
  if (!rawData?.length) {
    return [];
  }

  return rawData
    .filter(user => user.isActive)
    .map(transformUserData)
    .sort((a, b) => a.name.localeCompare(b.name));
};

// JSDoc for public APIs when needed
/**
 * Validates user permissions for specific actions
 */
export const hasPermission = (user: User, action: string): boolean => {
  return user.permissions.includes(action) || user.role === 'admin';
};

React-Specific Examples

Complex Form Development

## Step-by-Step Analysis

**Step 1: Analyze requirements**
- User form with validation for name, email, and role
- Real-time validation feedback
- Loading states during submission
- Error handling and user feedback

**Step 2: Choose implementation approach**
- useState for form data and validation errors
- useCallback for validation functions to prevent re-renders
- Progressive validation on blur events
- Accessible form structure with proper labels

**Step 3: Design validation strategy**
- Field-level validation with immediate feedback
- Form-level validation before submission
- Clear error messaging and error state management
- Prevent submission during loading state

**Step 4: Handle edge cases**
- Empty/undefined user prop for create vs edit modes
- Network errors during submission
- User cancellation and cleanup
- Keyboard accessibility and focus management

**Step 5: Validate solution meets requirements**
- Accessible form with proper ARIA labels
- TypeScript safety with proper prop types
- Reusable component that handles both create/edit modes
- Clean error handling with user-friendly messages

## Clean Implementation
```tsx
type UserFormProps = {
  user?: User;
  onSubmit: (data: UserFormData) => Promise<void>;
  onCancel?: () => void;
};

export const UserForm = ({ user, onSubmit, onCancel }: UserFormProps) => {
  const [formData, setFormData] = useState<UserFormData>(
    user || { name: '', email: '', role: 'user' }
  );
  const [errors, setErrors] = useState<Record<string, string>>({});
  const [isSubmitting, setIsSubmitting] = useState(false);

  const validateField = useCallback((field: keyof UserFormData, value: string) => {
    setErrors(prev => ({ ...prev, [field]: '' }));

    if (field === 'email' && !value.includes('@')) {
      setErrors(prev => ({ ...prev, email: 'Invalid email format' }));
      return false;
    }

    if (!value.trim()) {
      setErrors(prev => ({ ...prev, [field]: 'This field is required' }));
      return false;
    }

    return true;
  }, []);

  const handleSubmit = useCallback(async (e: FormEvent) => {
    e.preventDefault();

    const isValid = Object.keys(formData).every(field =>
      validateField(field as keyof UserFormData, formData[field])
    );

    if (!isValid) return;

    setIsSubmitting(true);
    try {
      await onSubmit(formData);
    } catch (error) {
      setErrors({ submit: error.message });
    } finally {
      setIsSubmitting(false);
    }
  }, [formData, onSubmit, validateField]);

  return (
    <form onSubmit={handleSubmit}>
      <div>
        <label htmlFor="name">Name</label>
        <input
          id="name"
          value={formData.name}
          onChange={(e) => setFormData(prev => ({ ...prev, name: e.target.value }))}
          onBlur={(e) => validateField('name', e.target.value)}
        />
        {errors.name && <span className="error">{errors.name}</span>}
      </div>

      <div>
        <button type="submit" disabled={isSubmitting}>
          {isSubmitting ? 'Saving...' : 'Save User'}
        </button>
        {onCancel && (
          <button type="button" onClick={onCancel}>Cancel</button>
        )}
      </div>

      {errors.submit && <div className="error">{errors.submit}</div>}
    </form>
  );
};

Key Decisions Made

• Used progressive validation for better UX
• Separated validation logic into reusable callback
• Implemented proper loading and error states
• Made component reusable for both create and edit modes

### Custom Hook Development

Step-by-Step Analysis

Step 1: Define hook requirements

• Generic data fetching with TypeScript support
• Configurable dependencies and enabled state
• Success and error callbacks for side effects
• Loading, error, and data states with computed properties

Step 2: Design hook interface

• Generic type parameter for data type safety
• Options object for configuration
• Return object with clear naming conventions
• Refetch function for manual data refresh

Step 3: Implement state management

• useState for data, loading, and error states
• useCallback for fetch function with proper dependencies
• useEffect for automatic data fetching with dependency array
• Proper cleanup and error handling

Step 4: Handle edge cases

• Disabled state when enabled is false
• Network errors and HTTP status errors
• Race conditions and component unmounting
• Callback error handling

Step 5: Optimize performance

• Memoized fetch function to prevent unnecessary re-renders
• Proper dependency arrays to control effect timing
• Computed states for better developer experience

Clean Implementation

type UseApiDataOptions<T> = {
  url: string;
  dependencies?: unknown[];
  enabled?: boolean;
  onSuccess?: (data: T) => void;
  onError?: (error: Error) => void;
};

export const useApiData = <T>({
  url,
  dependencies = [],
  enabled = true,
  onSuccess,
  onError
}: UseApiDataOptions<T>) => {
  const [data, setData] = useState<T | null>(null);
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState<Error | null>(null);

  const fetchData = useCallback(async () => {
    if (!enabled) return;

    setLoading(true);
    setError(null);

    try {
      const response = await fetch(url);
      if (!response.ok) throw new Error(`HTTP ${response.status}`);

      const result = await response.json();
      setData(result);
      onSuccess?.(result);

    } catch (err) {
      const error = err instanceof Error ? err : new Error('Unknown error');
      setError(error);
      onError?.(error);

    } finally {
      setLoading(false);
    }
  }, [url, enabled, onSuccess, onError]);

  useEffect(() => {
    fetchData();
  }, [fetchData, ...dependencies]);

  return {
    data,
    loading,
    error,
    refetch: fetchData,
    isSuccess: data !== null && !error,
    isError: error !== null,
  };
};

Key Decisions Made

• Generic type parameter for reusability across different data types
• Optional callbacks for side effects without forcing implementation
• Computed states (isSuccess, isError) for better developer experience
• Proper dependency management to prevent infinite loops

### State Management Flow

Step-by-Step Analysis

Step 1: Analyze data flow requirements

• User list needs to be shared across components
• Real-time updates from server
• Optimistic updates for better UX

Step 2: Choose appropriate state solution

• React Query for server state
• Context for UI state
• Local state for component-specific data

Step 3: Implement React Query integration

• Query configuration with proper caching
• Stale time and cache time optimization
• Query key structure for invalidation

Step 4: Design mutation strategy

• Optimistic updates for immediate feedback
• Rollback mechanism for error handling
• Cache updates on success

Step 5: Handle edge cases

• Race conditions during optimistic updates
• Network failures and retry logic
• Loading states and user feedback

Clean Implementation

// Step 1: Analyze data flow requirements
// - User list needs to be shared across components
// - Real-time updates from server
// - Optimistic updates for better UX

// Step 2: Choose appropriate state solution
// - React Query for server state
// - Context for UI state
// - Local state for component-specific data

// Step 3: Implement React Query integration
export const useUsers = () => {
  return useQuery({
    queryKey: ['users'],
    queryFn: fetchUsers,
    // Step 3a: Configure caching and refetching
    staleTime: 5 * 60 * 1000, // 5 minutes
    cacheTime: 10 * 60 * 1000, // 10 minutes
  });
};

// Step 4: Implement mutations with optimistic updates
export const useCreateUser = () => {
  const queryClient = useQueryClient();

  return useMutation({
    mutationFn: createUser,
    // Step 4a: Optimistic update
    onMutate: async (newUser) => {
      await queryClient.cancelQueries(['users']);
      const previousUsers = queryClient.getQueryData(['users']);

      queryClient.setQueryData(['users'], (old: User[]) => [
        ...old,
        { ...newUser, id: 'temp-' + Date.now() }
      ]);

      return { previousUsers };
    },
    // Step 4b: Handle success
    onSuccess: (data) => {
      queryClient.setQueryData(['users'], (old: User[]) =>
        old.map(user => user.id.startsWith('temp-') ? data : user)
      );
    },
    // Step 4c: Handle error with rollback
    onError: (err, newUser, context) => {
      queryClient.setQueryData(['users'], context?.previousUsers);
    },
  });
};

Key Decisions Made

• React Query for server state management instead of local state
• Optimistic updates to improve perceived performance
• Proper cache configuration to balance freshness and performance
• Rollback mechanism to handle network failures gracefully

Always make your logical progression clear and explicit.