Type Alias RequireExactlyOne<T, K>

RequireExactlyOne: {
    [P in K]: Required<Pick<T, P>> & Partial<Record<Exclude<K, P>, never>> & Omit<
        T,
        K,
    >
}[K]

Require exactly one property from a set of properties

Type Parameters

T
K extends keyof T = keyof T

Example

type Test = { a?: string; b?: number; c: boolean };
type Result = RequireExactlyOne<Test, 'a' | 'b'>;
// { a: string; b?: never; c: boolean } | { a?: never; b: number; c: boolean }