Thanks for taking up the maintenance on this project!

I am working with an XML schema which requires support for heterogeneous arrays of values within a set of specified types.

Consider the following enum which defines each of the types allowable:

enum AB {
    struct A: Decodable { let value: Int }
    struct B: Decodable { let value: String }
    case a(A)
    case b(B)   
}

Currently, the Decodable implementation is as follows (based on objc.io/codable-enums):

extension AB: Decodable {
    enum CodingKeys: String, CodingKey { case a, b }
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        do {
            self = .a(try container.decode(A.self, forKey: .a))
        } catch {
            self = .b(try container.decode(B.self, forKey: .b))
        }
    }
}

A minimal example of the source XML could look something like this (though there could be arbitrary amounts of either type, in any order):

let xml = """
<?xml version="1.0" encoding="UTF-8"?>
<container>
    <a value="42"></a>
    <b value="forty-two"></b>
</container>
"""

Upon decoding it with the XMLDecoder:

let decoder = XMLDecoder()
let abs: [AB] = try! decoder.decode([AB].self, from: xml.data(using: .utf8)!)

We get the following:

// => [.a(AB.A(value: 42))]

The desired result should be:

// => [.a(AB.A(value: 42)), .b(AB.B(value: "forty-two"))]

I have tried many combinations of keyed, unkeyed, singleValue, and nested containers, yet haven't found a solution that treats the data as an Array rather than a Dictionary.

Let me know if I am holding this wrong (at either the Decodable or the XMLDecoder stages), or if this could be a current limitation of the XMLCoder implementation. I'd be happy to contribute, but if anyone notices something glaring here, this would be very helpful.