Support nested unions when parsing FormData

[fehnomenal]

I have a schema that looks roughly like this (updated)

const morningSchema = z.literal('morning').transform(() => ({ from: '06:00', to: '11:00' }));

const noonSchema = z.literal('noon').transform(() => ({ from: '11:00', to: '14:00' }));

const eveningSchema = z.literal('evening').transform(() => ({ from: '14:00', to: '19:00' }));

const schema = z.object({
	time: z.union([morningSchema, noonSchema, eveningSchema])
});

This nested union was not supported for parsing FormData entries.

This PR fixes this use case by trying each union option until the first succeeds or throws an error describing the failed types.

I'm not sure if this breaks anything else. Tests pass and I didn't notice anything off.

---

My reasoning for having this is to get validation errors directly in one go. Otherwise I would have to parse it as a string, run a second pass and forward the issues to the main form.

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Name	Status	Preview	Comments	Updated (UTC)
superforms	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Dec 12, 2024 1:32pm

[fehnomenal]

I noticed it does not work correctly when the union is at the top-level of an object. Working on it.

[fehnomenal]

This works now, if the union or exactly on of its options has a default value.

[ciscoheat]

Thank you, but I'm not sure when this will be used, since your schema contains nested data and that should not be handled by the form data parser?

If you still think it's needed, can you add some test cases as well, so I get a better idea of what's happening? :)

[fehnomenal]

Oh, I'm sorry for getting back at you so late.

While simplifying the example schema I skipped some stuff. I will create some tests but the gist is that the schema will build more complex objects out of the posted strings.

[fehnomenal]

OK, I updated the first post, added a playground example and also some tests. Please have another look @ciscoheat