[swift-users] I've found a serious Bug in JSON encoding (SR-6631) and would like to fix it. [Sorry for the multiple posts]

[Benoit Pereira da silva]

Dear all

I've found a serious Bug in the JSON encoding foundations. [ SR-6631 <https://bugs.swift.org/browse/SR-6631> ]

This bug cause JSON encoding issues on Doubles when using a locale that does not use dot as decimal separator e.g « fr_FR » (we use a coma)
When using such a locale JSONEncoder & JSONSerialization encodes the Double value with the localized decimal separator. 

Code proof of the issue : 

import Foundation

// Required to call setLocale
import Darwin

// Let's set to french
setlocale(LC_ALL,"fr_FR")
 
struct Shot:Codable{
    let seconds:Double
}
 
let shot = Shot(seconds: 1.1)
 
do{
    let data = try JSONEncoder().encode(shot)
    if let json =  String(data:data, encoding:.utf8){
        // the result is : "{"seconds":1,1000000000000001} »
	// should be : "{"seconds":1.1000000000000001} »
        // The decimal separator should not be "," but "."
        print(json)
    }
}catch{
    print("\(error)")
}
 
exit(EX_OK)


Fix Proposal : 

 in swift-corelibs-foundation https://github.com/benoit-pereira-da-silva/swift-corelibs-foundation/blob/7bf5fc770471bcc6f9050cbdcd49492feccda2f2/Foundation/JSONSerialization.swift#L308 <https://github.com/benoit-pereira-da-silva/swift-corelibs-foundation/blob/7bf5fc770471bcc6f9050cbdcd49492feccda2f2/Foundation/JSONSerialization.swift#L308>
In `JSONSerialization.swift` line 308  may be should we specify  `kCFNumberFormatterDecimalSeparator` ? 
Adding :  CFNumberFormatterSetProperty(formatter, kCFNumberFormatterDecimalSeparator,CFSTR("."))

    private lazy var _numberformatter: CFNumberFormatter = {
        let formatter: CFNumberFormatter
        formatter = CFNumberFormatterCreate(nil, CFLocaleCopyCurrent(), kCFNumberFormatterNoStyle)
        CFNumberFormatterSetProperty(formatter, kCFNumberFormatterMaxFractionDigits, NSNumber(value: 15))
        CFNumberFormatterSetProperty(formatter, kCFNumberFormatterDecimalSeparator,CFSTR("."))
        CFNumberFormatterSetFormat(formatter, "0.###############"._cfObject)
        return formatter
    }()


I would like to propose my fix, test it and, but i’m not mastering the contribution mechanism.

Where should i start? 

I ve forked swift-corelibs-foundation <https://github.com/benoit-pereira-da-silva/swift-corelibs-foundation/blob/7bf5fc770471bcc6f9050cbdcd49492feccda2f2/Foundation/JSONSerialization.swift#L308>
How can i test my fix? 




Thanks



Benoit Pereira da Silva
Ultra Mobile Developer & Movement Activist
Développeur Ultra Mobile & Militant du mouvement
https://pereira-da-silva.com <https://pereira-da-silva.com/>





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