docs/rules/no-unused-prop-types.md
# Disallow definitions of unused propTypes (`react/no-unused-prop-types`)
<!-- end auto-generated rule header -->
Warns if a prop with a defined type isn't being used.
> **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:
```jsx
class Hello extends React.Component {
render() {
return <div>Hello Bob</div>;
}
}
Hello.propTypes = {
name: PropTypes.string
};
```
```jsx
type Props = {
firstname: string;
middlename: string; // middlename is never used by the Hello component
lastname: string;
}
class Hello extends React.Component<Props> {
render() {
return <div>Hello {this.props.firstname} {this.props.lastname}</div>;
}
}
```
```jsx
type Props = {
firstname: string;
lastname: string; // lastname isn't used by the Hello component
};
class Hello extends React.Component<Props> {
render() {
return <div>Hello {this.props.firstname}</div>;
}
}
class Greetings extends React.Component<Props> {
render() {
return <div>Greetings {this.props.firstname} {this.props.lastname}</div>;
}
}
```
Examples of **correct** code for this rule:
```jsx
class Hello extends React.Component {
render() {
return <div>Hello {this.props.name}</div>;
}
}
Hello.propTypes = {
name: PropTypes.string
};
```
## Rule Options
This rule can take one argument to ignore some specific props during validation.
```js
...
"react/no-unused-prop-types": [<enabled>, { ignore: <ignore>, customValidators: <customValidator>, skipShapeProps: <skipShapeProps> }]
...
```
- `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.
- `skipShapeProps`: In some cases it is impossible to accurately detect whether or not a `PropTypes.shape`'s values are being used. Setting this option to `true` will skip validation of `PropTypes.shape` (`true` by default).
## Known Issues/Limitations
- [False Positives: SFC (helper render methods)](#false-positives-sfc)
### False Positives SFC
Stateless Function Components (SFCs) accept props as an argument and return a JSX expression.
Even if the function gets called from a component, the props that are only used inside the component are not be considered used by a component.
Triggers false positive:
```js
function AComponent(props) {
function helperRenderer(aProp) { // is considered SFC
return (
<span>{aProp}{props.bProp}</span>
);
}
return (
<div>
{helperRenderer(props.aProp)}
</div>
);
}
AComponent.propTypes = {
aProp: PropTypes.string,
bProp: PropTypes.string // bProp is defined but never used
};
```
A suggested fix is to assign a bProp to a variable outside of the SFC.
```js
function AComponent(props) {
const { bProp } = props
function helperRenderer(aProp) { // is considered SFC
return (
<span>{aProp}{bProp}</span>
);
}
return (
<div>
{helperRenderer(props.aProp)}
</div>
);
}
AComponent.propTypes = {
aProp: PropTypes.string,
bProp: PropTypes.string
};
```
[PropTypes]: https://reactjs.org/docs/typechecking-with-proptypes.html
[TypeScript]: https://www.typescriptlang.org/
[Flow]: https://flow.org/