decoupling formatting logic and lazy loading formatter

1. moved format logic out of NSNumber and in to NSJSonSerialization
2. lazy load the formatter to be instantiated if needed
3. create a single format string to work with all formats since we are lazy loading a single formatter

Author: DaveLiu888

Foundation/NSJSONSerialization.swift

@@ -7,6 +7,8 @@
 // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 //
 
+import CoreFoundation
+
 #if os(OSX) || os(iOS)
     import Darwin
 #elseif os(Linux)
@@ -240,6 +242,14 @@ private struct JSONWriter {
     let pretty: Bool
     let writer: (String?) -> Void
 
+    private lazy var numberformatter: CFNumberFormatter = {
+        let formatter: CFNumberFormatter
+        formatter = CFNumberFormatterCreate(nil, CFLocaleCopyCurrent(), kCFNumberFormatterNoStyle)
+        CFNumberFormatterSetProperty(formatter, kCFNumberFormatterMaxFractionDigits, 15._bridgeToObject())
+        CFNumberFormatterSetFormat(formatter, "0.###############"._cfObject)
+        return formatter
+    }()
+
     init(pretty: Bool = false, writer: @escaping (String?) -> Void) {
         self.pretty = pretty
         self.writer = writer
@@ -298,15 +308,15 @@ private struct JSONWriter {
         writer("\"")
     }
 
-    func serializeNumber(_ num: NSNumber) throws {
+    mutating func serializeNumber(_ num: NSNumber) throws {
         if num.doubleValue.isInfinite || num.doubleValue.isNaN {
             throw NSError(domain: NSCocoaErrorDomain, code: NSCocoaError.PropertyListReadCorruptError.rawValue, userInfo: ["NSDebugDescription" : "Number cannot be infinity or NaN"])
         }
 
         // Cannot detect type information (e.g. bool) as there is no objCType property on NSNumber in Swift
         // So, just print the number
 
-        writer(num.serializationString)
+        writer(serializationString(for: num))
     }
 
     mutating func serializeArray(_ array: NSArray) throws {
@@ -389,6 +399,11 @@ private struct JSONWriter {
             writer(" ")
         }
     }
+    
+    //[SR-2151] https://bugs.swift.org/browse/SR-2151
+    private mutating func serializationString(for number: NSNumber) -> String {
+        return CFNumberFormatterCreateStringWithNumber(nil, numberformatter, number._cfObject)._swiftObject
+    }
 }
 
 //MARK: - JSONDeserializer

Foundation/NSNumber.swift

@@ -450,23 +450,8 @@ open class NSNumber : NSValue {
     open override var description: String {
         return description(withLocale: nil)
     }
-
-    //[SR-2151] https://bugs.swift.org/browse/SR-2151
-    internal var serializationString: String {
-        let formatter: CFNumberFormatter
-        formatter = CFNumberFormatterCreate(nil, CFLocaleCopyCurrent(), kCFNumberFormatterNoStyle)
-        CFNumberFormatterSetProperty(formatter, kCFNumberFormatterMaxFractionDigits, 15._bridgeToObject())
-        switch  CFNumberGetType(_cfObject as CFNumber){
-            case .floatType, .float32Type, .float64Type, .cgFloatType, .doubleType:
-                CFNumberFormatterSetFormat(formatter, "0.###############"._cfObject);
-            default:break
-        }
-        return CFNumberFormatterCreateStringWithNumber(nil, formatter, self._cfObject)._swiftObject
-    }
 }
 
-
-
 extension CFNumber : _NSBridgable {
     typealias NSType = NSNumber
     internal var _nsObject: NSType { return unsafeBitCast(self, to: NSType.self) }

TestFoundation/TestNSJSONSerialization.swift

@@ -691,9 +691,19 @@ extension TestNSJSONSerialization {
                 XCTAssertEqual(str!, "{\"\(param.0)\":\(param.0._bridgeToObject().intValue)}", "expect that serialized value should not contain trailing zero or decimal as they are whole numbers ")
             }
         }
+        
+        func excecute_testWholeNumbersWithIntInput() {
+            for i  in -10..<10 {
+                let iStr = "\(i)"
+                let testDict = [iStr : i as AnyObject] as [String : AnyObject]
+                let str = try? trySerialize(testDict.bridge())
+                XCTAssertEqual(str!, "{\"\(iStr)\":\(i)}", "expect that serialized value should not contain trailing zero or decimal as they are whole numbers ")
+            }
+        }
         excecute_testSetLessThanOne()
         excecute_testSetGraterThanOne()
         excecute_testWholeNumbersWithDoubleAsInput()
+        excecute_testWholeNumbersWithIntInput()
     }
 
     func test_serialize_null() {