React Patterns

Core Rules

• Use functional components with hooks exclusively (no class components)
• Use proper dependency arrays in useEffect
• Follow the existing component structure
• Use React 19 features and patterns
• Import modules from React: import module from react. Do not use inline React.[module]

Component Structure

// ComponentName/ComponentName.tsx — import directly, no index.ts barrel
interface ComponentNameProps {
  ...
}

export const ComponentName = ({ }: ComponentNameProps) => {
  ...
  return (
    ...
  );
};

Custom Hooks

• Prefix with use
• Return objects for multiple values, not arrays
• Use proper TypeScript return types
• Follow existing patterns in src/hooks/

Provider Pattern

const Context = createContext<ContextType | null>(null);

export const Provider = ({ children }: { children: ReactNode }) => {
  ...
  return <Context.Provider value={value}>{children}</Context.Provider>;
};

export const useContext = () => {
  const context = useContext(Context);
  if (!context) throw new Error('useContext must be used within Provider');
  return context;
};

State Management

• Use Tanstack Query for server state
• Use Tanstack Router for routing
• Use React hooks for local component state
• Use Context providers for app-wide state (see existing providers in src/providers/)
• Use useRequiredContext to simplify context usage and avoid null checks

React Compiler

This project uses the React Compiler for automatic memoization. Files/directories are incrementally adopted in react-compiler.config.js.

Writing React Compiler Compatible Code

For new files, ensure they follow React Compiler rules from the start:

1. Don't mutate values during render

   // Bad - mutating during render
   const items = props.items;
   items.push(newItem);
   
   // Good - create new reference
   const items = [...props.items, newItem];
   

2. Don't read/write refs during render

   // Bad - reading ref during render
   const value = myRef.current;
   return <div>{value}</div>;
   
   // Good - read refs in effects or callbacks
   useEffect(() => {
     const value = myRef.current;
   }, []);
   

3. Follow Rules of Hooks strictly - no conditional hooks, no hooks in loops, proper dependency arrays

4. Avoid patterns the compiler can't optimize

   • Don't spread props with {...props} unnecessarily
   • Avoid dynamic property access on objects when possible
   • Keep component logic predictable

Adding Files to React Compiler

When a file is added to react-compiler.config.js:

• Remove unnecessary useCallback and useMemo (compiler handles this)
• Verify no compiler violations with pnpm run validate
• Test the component still works correctly
• Consolidate entries by folder when all files in a directory are compiler-enabled (e.g., use /path/to/folder instead of listing each file individually)

React Compiler Config Structure

Files are organized by cleanup effort in react-compiler.config.js:

• Top section: Already enabled directories/files
• Middle: Ready to enable (0 useCallback/useMemo)
• Bottom (commented): Need cleanup before enabling

Performance

• Do not use useMemo, useCallback, or memo manually — the React Compiler handles memoization automatically
• If you encounter existing useMemo/useCallback/memo in a file, remove them when the file is enabled in react-compiler.config.js
• Lazy load heavy components when possible
• Follow existing patterns for optimization