JSONSerialization re-encodes Decimal as Double #1115
Description
I am using JSONSerialization to sort keys for arbitrary JSON represented as String:
func sortedJSON(_ string: String) -> String? {
guard let data = string.data(using: .utf8),
let json = try? JSONSerialization.jsonObject(with: data, options: []),
let sortedData = try? JSONSerialization.data(withJSONObject: json, options: [.sortedKeys])
else {
return nil
}
return .init(data: sortedData, encoding: .utf8)
}
/// example of usage
enum DecimalContainting: Codable {
case decimal(Decimal)
}
let decimal = DecimalContainting.decimal(Decimal(string: "129.9")!)
let jsonEncoder = JSONEncoder()
let data = try jsonEncoder.encode(decimal)
let jsonUnsortedString = String(data: data, encoding: .utf8)
let jsonSortedString = jsonUnsortedString.flatMap { sortedJSON($0) }
print(jsonUnsortedString)
print(jsonSortedString)The output is surprisingly different for sorted and unsorted data:
Optional("{\"decimal\":{\"_0\":129.9}}")
Optional("{\"decimal\":{\"_0\":129.90000000000001}}")
Notably, this happens on MacOS but if I run the same code on linux, the output is the same for both:
Optional("{\"decimal\":{\"_0\":129.9}}")
Optional("{\"decimal\":{\"_0\":129.9}}")
Swift version macOS:
$ swift --version
swift-driver version: 1.115.1 Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1)
Swift version Linux:
$ swift --version
Swift version 6.0.1 (swift-6.0.1-RELEASE)