Hmm, this is pretty interesting, but I still have issues. While Zod seems to be able to transform my server-returned object into a discriminated union, it doesn't seem to be able to tell which of the unions it is. For instance, say that api/user/mod-panel (e.g.) returns only moderator user objects. My API endpoint already knows that it will have moderator-related fields, but Zod forgets that when I parse it.
You can use an ‘is’ method to pick out a type from union. Although, if union is discriminated, it’s discriminated with a ‘kind’ so you should be able to know which kind you received.
I am not totally sure what your API's look like but if you know the API only has a certain type (or subset of types), you would only validate that type on the method. Don't use a single union for everything.
Here is some pseudocode.
Person = { name: string, height: number }
Animal = {name: string, capability: string}
A = { post: object, methodType: string, person: Person }
You can define all the different sub types separately and make the discriminated union using them. The use only a single type for an endpoint if it only uses a single type. Only use the discriminated union where you actually might be handling multiple types.
