Proposal: FlipOptional
type OptionalKeys<T> = {
[K in keyof T]-?: {} extends Pick<T, K> ? K : never
}[keyof T];
type FlipOptional<T> = (Required<Pick<T, OptionalKeys<T>>> &
Partial<Omit<T, OptionalKeys<T>>>) extends infer O
? { [K in keyof O]: O[K] }
: never;Taken from https://stackoverflow.com/a/57593506/1154610.
A practical example is a TypeScript equivalent of ESLint rule react/require-default-props.
import React from 'react';
export interface InputProps {
className?: string;
name: string;
}
export default class Input extends React.Component<InputProps> {
static defaultProps: FlipOptional<InputProps> = {
// className is required for defaultProps.
className: null
// name is optional for defaultProps.
}
render() {
const { className, name } = this.props;
return <input className={className} name={name} />
}
}
sindresorhus / type-fest
A collection of essential TypeScript types
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