JSONSerialization: Add support for .withoutEscapingSlashes, .fragmentsAllowed

Author: spevans

Foundation/JSONSerialization.swift

@@ -25,6 +25,8 @@ extension JSONSerialization {
 
         public static let prettyPrinted = WritingOptions(rawValue: 1 << 0)
         public static let sortedKeys = WritingOptions(rawValue: 1 << 1)
+        public static let fragmentsAllowed = WritingOptions(rawValue: 1 << 2)
+        public static let withoutEscapingSlashes = WritingOptions(rawValue: 1 << 3)
     }
 }
 
@@ -139,8 +141,7 @@ open class JSONSerialization : NSObject {
         var jsonStr = [UInt8]()
 
         var writer = JSONWriter(
-            pretty: opt.contains(.prettyPrinted),
-            sortedKeys: opt.contains(.sortedKeys),
+            options: opt,
             writer: { (str: String?) in
                 if let str = str {
                     jsonStr.append(contentsOf: str.utf8)
@@ -157,7 +158,10 @@ open class JSONSerialization : NSObject {
         } else if let container = value as? Dictionary<AnyHashable, Any> {
             try writer.serializeJSON(container)
         } else {
-            fatalError("Top-level object was not NSArray or NSDictionary") // This is a fatal error in objective-c too (it is an NSInvalidArgumentException)
+            guard opt.contains(.fragmentsAllowed) else {
+                fatalError("Top-level object was not NSArray or NSDictionary") // This is a fatal error in objective-c too (it is an NSInvalidArgumentException)
+            }
+            try writer.serializeJSON(value)
         }
 
         let count = jsonStr.count
@@ -301,11 +305,13 @@ private struct JSONWriter {
     var indent = 0
     let pretty: Bool
     let sortedKeys: Bool
+    let withoutEscapingSlashes: Bool
     let writer: (String?) -> Void
 
-    init(pretty: Bool = false, sortedKeys: Bool = false, writer: @escaping (String?) -> Void) {
-        self.pretty = pretty
-        self.sortedKeys = sortedKeys
+    init(options: JSONSerialization.WritingOptions, writer: @escaping (String?) -> Void) {
+        pretty = options.contains(.prettyPrinted)
+        sortedKeys = options.contains(.sortedKeys)
+        withoutEscapingSlashes = options.contains(.withoutEscapingSlashes)
         self.writer = writer
     }
 
@@ -379,7 +385,8 @@ private struct JSONWriter {
                 case "\\":
                     writer("\\\\") // U+005C reverse solidus
                 case "/":
-                    writer("\\/") // U+002F solidus
+                    if !withoutEscapingSlashes { writer("\\") }
+                    writer("/") // U+002F solidus
                 case "\u{8}":
                     writer("\\b") // U+0008 backspace
                 case "\u{c}":

TestFoundation/TestJSONSerialization.swift

@@ -1013,6 +1013,8 @@ extension TestJSONSerialization {
             ("test_serialize_Decimal", test_serialize_Decimal),
             ("test_serialize_NSDecimalNumber", test_serialize_NSDecimalNumber),
             ("test_serialize_stringEscaping", test_serialize_stringEscaping),
+            ("test_serialize_fragments", test_serialize_fragments),
+            ("test_serialize_withoutEscapingSlashes", test_serialize_withoutEscapingSlashes),
             ("test_jsonReadingOffTheEndOfBuffers", test_jsonReadingOffTheEndOfBuffers),
             ("test_jsonObjectToOutputStreamBuffer", test_jsonObjectToOutputStreamBuffer),
             ("test_jsonObjectToOutputStreamFile", test_jsonObjectToOutputStreamFile),
@@ -1371,6 +1373,26 @@ extension TestJSONSerialization {
         XCTAssertEqual(try trySerialize(json), "[\"j\\/\"]")
     }
 
+    func test_serialize_fragments() {
+        XCTAssertEqual(try trySerialize(2, options: .fragmentsAllowed), "2")
+        XCTAssertEqual(try trySerialize(false, options: .fragmentsAllowed), "false")
+        XCTAssertEqual(try trySerialize(true, options: .fragmentsAllowed), "true")
+        XCTAssertEqual(try trySerialize(Float(1), options: .fragmentsAllowed), "1")
+        XCTAssertEqual(try trySerialize(Double(2), options: .fragmentsAllowed), "2")
+        XCTAssertEqual(try trySerialize(Decimal(Double.leastNormalMagnitude), options: .fragmentsAllowed), "0.0000000000000000000000000000000000000000000000000002225073858507201792")
+        XCTAssertEqual(try trySerialize("test", options: .fragmentsAllowed), "\"test\"")
+    }
+
+    func test_serialize_withoutEscapingSlashes() {
+        // .withoutEscapingSlashes controls whether a "/" is encoded as "\\/" or "/"
+        let testString      = "This /\\/ is a \\ \\\\ \\\\\\ \"string\"\n\r\t\u{0}\u{1}\u{8}\u{c}\u{f}"
+        let escapedString   = "\"This \\/\\\\\\/ is a \\\\ \\\\\\\\ \\\\\\\\\\\\ \\\"string\\\"\\n\\r\\t\\u0000\\u0001\\b\\f\\u000f\""
+        let unescapedString = "\"This /\\\\/ is a \\\\ \\\\\\\\ \\\\\\\\\\\\ \\\"string\\\"\\n\\r\\t\\u0000\\u0001\\b\\f\\u000f\""
+
+        XCTAssertEqual(try trySerialize(testString, options: .fragmentsAllowed), escapedString)
+        XCTAssertEqual(try trySerialize(testString, options: [.withoutEscapingSlashes, .fragmentsAllowed]), unescapedString)
+    }
+
     /* These are a programming error and should not be done
        Ideally the interface for JSONSerialization should at compile time prevent this type of thing
        by overloading the interface such that it can only accept dictionaries and arrays.