JSON encoding of Double differs between platforms

[amomchilov]

I opened this issue kishikawakatsumi/swift-power-assert#436 about some failing unit tests, and it turns out to be platform dependant. From that thread:

iOS 17, Sonoma and Linux

{"foundingYear":1957,"location":{"longitude":139.745438,"latitude":35.658581},"name":"Tokyo > Tower"}

iOS 16.x and macOS Monterey

{"name":"Tokyo Tower","location":{"longitude":139.74543800000001,"latitude":35.658580999999998},"foundingYear":1957}

Given the OSes impacted, I'm guessing this was causing by the transition to the Swift-native Foundation impl on Apple platforms.

Is this difference in Double formatting intentional?

SwiftFiddle

demo.swift

import Foundation

struct Coordinate: Codable {
  var latitude: Double
  var longitude: Double
}

struct Landmark: Codable {
  var name: String
  var foundingYear: Int
  var location: Coordinate
}

let landmark = Landmark(
  name: "Tokyo Tower",
  foundingYear: 1957,
  location: Coordinate(latitude: 35.658581, longitude: 139.745438)
)

let data = try JSONEncoder().encode(landmark)
print(String(data: data, encoding: .utf8)!)
print(data.count)
print(data as NSData) // NSData gives a better description

[iCharlesHu]

@kperryua could you please take a look?