prop-types.md

Disallow missing props validation in a React component definition (react/prop-types)

💼 This rule is enabled in the ☑️ recommended config.

Defining types for component props improves reusability of your components by validating received data. It can warn other developers if they make a mistake while reusing the component with improper data type.

Note: You can provide types in runtime types using PropTypes and/or statically using TypeScript or Flow. This rule will validate your prop types regardless of how you define them.

Rule Details

Examples of incorrect code for this rule:

function Hello({ name }) {
  return <div>Hello {name}</div>;
  // 'name' is missing in props validation
}

var Hello = createReactClass({
  propTypes: {
    firstname: PropTypes.string.isRequired
  },
  render: function() {
    return <div>Hello {this.props.firstname} {this.props.lastname}</div>;
    // 'lastname' type is missing in props validation
  }
});

// Or in ES6
class Hello extends React.Component {
  render() {
    return <div>Hello {this.props.firstname} {this.props.lastname}</div>;
    // 'lastname' type is missing in props validation
  }
}
Hello.propTypes = {
  firstname: PropTypes.string.isRequired
}

In TypeScript:

interface Props {
  age: number
}
function Hello({ name }: Props) {
  return <div>Hello {name}</div>;
  // 'name' type is missing in props validation
}

Examples of correct code for this rule:

function Hello({ name }) {
  return <div>Hello {name}</div>;
}
Hello.propTypes = {
  name: PropTypes.string.isRequired
}

var Hello = createReactClass({
  propTypes: {
    name: PropTypes.string.isRequired,
  },
  render: function() {
    return <div>Hello {this.props.name}</div>;
  },
});

// Or in ES6:
class HelloEs6 extends React.Component {
  render() {
    return <div>Hello {this.props.name}</div>;
  }
}
HelloEs6.propTypes = {
  name: PropTypes.string.isRequired,
};

// ES6 + Public Class Fields (draft: https://tc39.github.io/proposal-class-public-fields/)
class HelloEs6WithPublicClassField extends React.Component {
  static propTypes = {
    name: PropTypes.string.isRequired,
  }
  render() {
    return <div>Hello {this.props.name}</div>;
  }
}

In TypeScript:

// destructured default prop values

function Foo({ bar = "" }): JSX.Element {
  return <div>{bar}</div>;
}

function Foo({ bar = "" as string }): JSX.Element {
  return <div>{bar}</div>;
}

In Flow:

type Props = {
  name: string
}
class Hello extends React.Component<Props> {
  render() {
    return <div>Hello {this.props.name}</div>;
  }
}

Examples of correct code for this rule:

function Hello() {
  return <div>Hello World</div>;
}

// Referencing an external object disable the rule for the component
function Hello({ name }) {
  return <div>Hello {name}</div>;
}
Hello.propTypes = myPropTypes;

Rule Options

This rule can take one argument to ignore some specific props during validation.

...
"react/prop-types": [<enabled>, { ignore: <ignore>, customValidators: <customValidator>, skipUndeclared: <skipUndeclared> }]
...

• enabled: for enabling the rule. 0=off, 1=warn, 2=error. Defaults to 0.
• ignore: optional array of props name to ignore during validation.
• customValidators: optional array of validators used for propTypes validation.
• skipUndeclared: optional boolean to only error on components that have a propTypes block declared.

As for "exceptions"

It would seem that some common properties such as props.children or props.className (and alike) need to be treated as exceptions.

As it aptly noticed in #7

Why should children be an exception? Most components don't need this.props.children, so that makes it extra important to document children in the prop types.

Generally, you should use PropTypes.node or static type React.Node for children. It accepts anything that can be rendered: numbers, strings, elements or an array containing these types.

Since 2.0.0 children is no longer ignored for props validation.

About component detection

For this rule to work we need to detect React components, this could be very hard since components could be declared in a lot of ways.

For now we should detect components created with:

• a function that return JSX or the result of a React.createElement call.
• createReactClass()
• an ES6 class that inherit from React.Component or Component