prop-types.md

Prevent missing props validation in a React component definition (prop-types)

PropTypes improve the reusability of your component by validating the received data.

It can warn other developers if they make a mistake while reusing the component with improper data type.

Rule Details

The following patterns are considered warnings:

var Hello = React.createClass({
  render: function() {
    return <div>Hello {this.props.name}</div>;
  }
});

var Hello = React.createClass({
  propTypes: {
    firstname: React.PropTypes.string.isRequired
  },
  render: function() {
    return <div>Hello {this.props.firstname} {this.props.lastname}</div>; // lastname type is not defined in propTypes
  }
});

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

Examples of correct usage without warnings:

var Hello = React.createClass({
  propTypes: {
    name: React.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: React.PropTypes.string.isRequired,
};

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

The following patterns are not considered warnings:

var Hello = React.createClass({
  render: function() {
    return <div>Hello World</div>;
  }
});

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

// Referencing an external object disable the rule for the component
var Hello = React.createClass({
  propTypes: myPropTypes,
  render: function() {
    return <div>Hello {this.props.name}</div>;
  }
});

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

Rule Options

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

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

• 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: 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 propTypes.

Generally, you should use React.PropTypes.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:

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