upstream-twenty/packages/twenty-docs/developers/contribute/style-guide.mdx

---
title: Style Guide
icon: "paintbrush"
description: Code conventions and best practices for contributing to Twenty.
---

## React

### Functional components only

Always use TSX functional components with named exports.

```tsx
// ❌ Bad
const MyComponent = () => {
  return <div>Hello World</div>;
};
export default MyComponent;

// ✅ Good
export function MyComponent() {
  return <div>Hello World</div>;
};
```

### Props

Create a type named `{ComponentName}Props`. Use destructuring. Don't use `React.FC`.

```tsx
type MyComponentProps = {
  name: string;
};

export const MyComponent = ({ name }: MyComponentProps) => <div>Hello {name}</div>;
```

### No single-variable prop spreading

```tsx
// ❌ Bad
const MyComponent = (props: MyComponentProps) => <Other {...props} />;

// ✅ Good
const MyComponent = ({ prop1, prop2 }: MyComponentProps) => <Other {...{ prop1, prop2 }} />;
```

## State Management

### Jotai atoms for global state

```tsx
import { createAtomState } from '@/ui/utilities/state/jotai/utils/createAtomState';
import { useAtomState } from '@/ui/utilities/state/jotai/hooks/useAtomState';

export const myAtomState = createAtomState<string>({
  key: 'myAtomState',
  defaultValue: 'default value',
});
```

- Prefer atoms over prop drilling
- Don't use `useRef` for state — use `useState` or atoms
- Use atom families and selectors for lists

### Avoid unnecessary re-renders

- Extract `useEffect` and data fetching into sibling sidecar components
- Prefer event handlers (`handleClick`, `handleChange`) over `useEffect`
- Don't use `React.memo()` — fix the root cause instead
- Limit `useCallback` / `useMemo` usage

```tsx
// ❌ Bad — useEffect in the same component causes re-renders
export const Page = () => {
  const [data, setData] = useAtomState(dataState);
  const [dep] = useAtomState(depState);
  useEffect(() => { setData(dep); }, [dep]);
  return <div>{data}</div>;
};

// ✅ Good — extract into sibling
export const PageData = () => {
  const [data, setData] = useAtomState(dataState);
  const [dep] = useAtomState(depState);
  useEffect(() => { setData(dep); }, [dep]);
  return <></>;
};
export const Page = () => {
  const [data] = useAtomState(dataState);
  return <div>{data}</div>;
};
```

## TypeScript

- **`type` over `interface`** — more flexible, easier to compose
- **String literals over enums** — except for GraphQL codegen enums and internal library APIs
- **No `any`** — strict TypeScript enforced
- **No type imports** — use regular imports (enforced by Oxlint `typescript/consistent-type-imports`)
- **Use [Zod](https://github.com/colinhacks/zod)** for runtime validation of untyped objects

## JavaScript

```tsx
// Use nullish-coalescing (??) instead of ||
const value = process.env.MY_VALUE ?? 'default';

// Use optional chaining
onClick?.();
```

## Naming

- **Variables**: camelCase, descriptive (`email` not `value`, `fieldMetadata` not `fm`)
- **Constants**: SCREAMING_SNAKE_CASE
- **Types/Classes**: PascalCase
- **Files/directories**: kebab-case (`.component.tsx`, `.service.ts`, `.entity.ts`)
- **Event handlers**: `handleClick` (not `onClick` for the handler function)
- **Component props**: prefix with component name (`ButtonProps`)
- **Styled components**: prefix with `Styled` (`StyledTitle`)

## Styling

Use [Linaria](https://github.com/callstack/linaria) styled components. Use theme values — avoid hardcoded `px`, `rem`, or colors.

```tsx
// ❌ Bad
const StyledButton = styled.button`
  color: #333333;
  font-size: 1rem;
  margin-left: 4px;
`;

// ✅ Good
const StyledButton = styled.button`
  color: ${({ theme }) => theme.font.color.primary};
  font-size: ${({ theme }) => theme.font.size.md};
  margin-left: ${({ theme }) => theme.spacing(1)};
`;
```

## Imports

Use aliases instead of relative paths:

```tsx
// ❌ Bad
import { Foo } from '../../../../../testing/decorators/Foo';

// ✅ Good
import { Foo } from '~/testing/decorators/Foo';
import { Bar } from '@/modules/bar/components/Bar';
```

## Folder Structure

```
front
└── modules/         # Feature modules
│   └── module1/
│       ├── components/
│       ├── constants/
│       ├── contexts/
│       ├── graphql/  (fragments, queries, mutations)
│       ├── hooks/
│       ├── states/   (atoms, selectors)
│       ├── types/
│       └── utils/
└── pages/           # Route-level components
└── ui/              # Reusable UI components (display, input, feedback, ...)
```

- Modules can import from other modules, but `ui/` should stay dependency-free
- Use `internal/` subfolders for module-private code
- Components under 300 lines, services under 500 lines