Is it possible to create a type that accepts an object with any properties, but requires at least one (unknown) property to be defined?
// attempting to implement this
type CustomType = {
[key: string]: any
}
const customObj: CustomType = {} // this should trigger an error
const newCustomObj: CustomType = { something: "thing" } // this should be valid
Thanks to the input from @Fahd Lihidheb, this solution is what comes to mind:
type NotEmpty<T> = keyof T extends never ? never : T
function createTest<T extends {[key: string]: any}>(test: NotEmpty<T>): T {
return test
}
const obj = createTest({}) // error
const anotherObj = createTest({ something: "thing" }) // works
Just defining a type may not be enough. Using a factory method allows us to dynamically infer the type of T and verify if any keys are present.
While occupied with another task, I stumbled across a potential solution.
type NonEmptyObj<T extends Record<string, unknown>> = T extends Record<string, never> ? never : T;
This method relies on Record<string, never> to define an empty object and checks if T does not extend an empty object.
If implemented, it would appear like this:
function someFunction<T extends Record<string, unknown>>(foo: NonEmptyObject<T>) { ... }
Is this advisable? Probably not. The error message generated by this type check is not very helpful, and the potential application is quite limited.
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