Add SingleKey and IfEmptyObject

[ash-zzz]

Closes #813

I also added IfEmptyObject since that was a missing guard type that I needed to use for this

[sindresorhus]

I think it should be named SingleKeyObject. The current name is a bit ambiguous and could make you single it fetches a single key from an object, for example.

[sindresorhus]

Leftover

[ash-zzz]

Oops I thought I removed them all

[sindresorhus]

Suggested change

	*/
	*/

[sindresorhus]

Document the actual compilation here.

[sindresorhus]

Keep the example simple by not using a nested property here.

[ash-zzz]

I think it should be named SingleKeyObject. The current name is a bit ambiguous and could make you single it fetches a single key from an object, for example.

Agreed, I just renamed it and fixed the documentation

[sindresorhus]

Thanks :)

[jakeboone02]

Thanks for doing this, @ash-zzz!

Should this work for types where the keys are unrestricted? If not, I'm not sure it satisfies my original request from #813, which was to declare an object type that requires exactly one key without restricting the key itself to any specific string or union of strings.

I tried SingleKeyObject<Record<string, any>> and SingleKeyObject<{ [k: string]: any }> but they both resolved to never. Something like SingleKeyObject<Record<'union' | 'of' | 'strings', any>> works fine.