I have a union of two types, one of which is an empty obj.
type U = {} | { a: number } // | { b: string } | { c: boolean } ....
I would like to exclude the empty object from the union however Exclude
is no help
type A = Exclude<U, {}>
// A = never
I tried using as const
but it's the same result
const empty = {} as const
type Empty = typeof empty
type U = Empty | { a: number }
type A = Exclude<U, Empty>
//type A = never
The extra Irony is that excluding the other properties is straightforward
type B = Exclude<U, { a: number }>
// type B = {}
So is it possible to exclude an empty interface from other interfaces in a union?
Answering my own question..
If you use AtLeastOne
from @lukasgeiter answer here: Exclude empty object from Partial type
you can do the following:
type AtLeastOne<T, U = {[K in keyof T]: Pick<T, K> }> = Partial<T> & U[keyof U];
type ExcludeEmpty<T> = T extends AtLeastOne<T> ? T : never;
type U = {} | { a: number } | { b: string }
type Foo = ExcludeEmpty<U> // { a: number } | { b: string }