JSONEncoder bug when dictionary key is enum?

[Ponyboy47 (Jacob Williams)]

import Foundation
enum Foo: String, Encodable { 
    case asc
    case desc
}
let foobar: [Foo: String] = [.desc: "testing"]
let encoder = JSONEncoder()
let data = try encoder.encode(foobar)
print(String(data: data, encoding: .utf8)!)

// Prints: ["desc","testing"]

This is a simplified example that demonstrates an issue I have been encountering in a project I'm working on. When the key of a dictionary is an enum, the JSONEncoder encodes it as an array and not as a dictionary.

I am able to reproduce this on both swift 5.3 and 5.2.4

[Lantua]

You may want to check out this thread:

Encoding/Decoding a Swift Dictionary to/from JSON

Specifically, it treats Int and String as CodingKeys with the equivalent intValue/stringValue which allows it to encode as an actual dictionary as opposed to the more general types. From the last time @Lantua and I discussed this (), see the links below for some more background on this: If you need to specifically maintain a dictionary format here, your best bet is to encode and decode as [Int: String] but perform the conversion to Int32 afterwards.

[Ponyboy47 (Jacob Williams)]

Thanks @Lantua! Good to know why it's happening although it is a frustrating limitation. Since the enum has a string rawValue I can just transform the keys to strings prior to encoding.