zod union vs XOR / exclusive OR

[jonathanstanley]

z.union([...]) and mySchema.or(...) is NOT an XOR (exclusive or):

zod/src/types.ts

Lines 2757 to 2760 in f59be09

	// return first issue-free validation if it exists
	for (const result of results) {
	if (result.result.status === "valid") {
	return result.result;

zod marks a success as soon as any successful schema is found. this is faster than XOR.

In special cases, this might give surprising results (ie: those receiving messy objects/unions from third parties without a discriminated union). FWIW: XOR is also tricky in typescript.

see also
#2325 union in objects error / undefined
#2106 deprecating discriminated union?

[rubengmurray]

Was trying to find my own post (#2797) and came across this. Linking for reference.