Fix swiftlang#1176 JSON Decoder and Encoder limit disagreement (swiftlang#1242)

* Add test case to reproduce JSON bug

* Increment encoding limit by 1 to match decoding behavior

* Move checking condition & add expect fail test

* Skip failing test on windows

Author: jevonmao

Sources/FoundationEssentials/JSON/JSONScanner.swift

@@ -265,6 +265,7 @@ internal struct JSONScanner {
     var reader: DocumentReader
     var depth: Int = 0
     var partialMap = JSONPartialMapData()
+    private static let maximumRecursionDepth = 512
 
     internal struct Options {
         var assumesTopLevelDictionary = false
@@ -412,7 +413,7 @@ internal struct JSONScanner {
     mutating func scanArray() throws {
         let firstChar = reader.read()
         precondition(firstChar == ._openbracket)
-        guard self.depth < 512 else {
+        guard self.depth < Self.maximumRecursionDepth else {
             throw JSONError.tooManyNestedArraysOrDictionaries(location: reader.sourceLocation(atOffset: 1))
         }
         self.depth &+= 1
@@ -470,7 +471,7 @@ internal struct JSONScanner {
     mutating func scanObject() throws {
         let firstChar = self.reader.read()
         precondition(firstChar == ._openbrace)
-        guard self.depth < 512 else {
+        guard self.depth < Self.maximumRecursionDepth else {
             throw JSONError.tooManyNestedArraysOrDictionaries(location: reader.sourceLocation(atOffset: -1))
         }
         try scanObject(withoutBraces: false)

Sources/FoundationEssentials/JSON/JSONWriter.swift

@@ -29,6 +29,9 @@ internal struct JSONWriter {
     }
 
     mutating func serializeJSON(_ value: JSONEncoderValue, depth: Int = 0) throws {
+        guard depth < Self.maximumRecursionDepth else {
+            throw JSONError.tooManyNestedArraysOrDictionaries()
+        }
         switch value {
         case .string(let str):
             serializeString(str)
@@ -172,10 +175,6 @@ internal struct JSONWriter {
     }
 
     mutating func serializeArray(_ array: [JSONEncoderValue], depth: Int) throws {
-        guard depth < Self.maximumRecursionDepth else {
-            throw JSONError.tooManyNestedArraysOrDictionaries()
-        }
-
         writer(ascii: ._openbracket)
         if pretty {
             writer(ascii: ._newline)
@@ -204,10 +203,6 @@ internal struct JSONWriter {
     }
 
     mutating func serializePreformattedByteArray(_ bytes: [UInt8], _ lengths: [Int], depth: Int) throws {
-        guard depth < Self.maximumRecursionDepth else {
-            throw JSONError.tooManyNestedArraysOrDictionaries()
-        }
-
         writer(ascii: ._openbracket)
         if pretty {
             writer(ascii: ._newline)
@@ -242,10 +237,6 @@ internal struct JSONWriter {
     }
 
     mutating func serializeObject(_ dict: [String:JSONEncoderValue], depth: Int) throws {
-        guard depth < Self.maximumRecursionDepth else {
-            throw JSONError.tooManyNestedArraysOrDictionaries()
-        }
-
         writer(ascii: ._openbrace)
         if pretty {
             writer(ascii: ._newline)

Tests/FoundationEssentialsTests/JSONEncoderTests.swift

@@ -2492,13 +2492,19 @@ extension JSONEncoderTests {
         prettyPrintEncoder.outputFormatting = .prettyPrinted
 
         for encoder in [JSONEncoder(), prettyPrintEncoder] {
-            let reencodedData = try! encoder.encode(decoded)
-            let redecodedObjects = try! decoder.decode(T.self, from: reencodedData)
-            XCTAssertEqual(decoded, redecodedObjects)
-
-            if let plistData {
-                let decodedPlistObjects = try! PropertyListDecoder().decode(T.self, from: plistData)
-                XCTAssertEqual(decoded, decodedPlistObjects)
+            do {
+                let reencodedData = try encoder.encode(decoded)
+                let redecodedObjects = try decoder.decode(T.self, from: reencodedData)
+                XCTAssertEqual(decoded, redecodedObjects)
+
+                if let plistData {
+                        let decodedPlistObjects = try PropertyListDecoder().decode(T.self, from: plistData)
+                        XCTAssertEqual(decoded, decodedPlistObjects)
+                    
+                }
+            }
+            catch {
+                XCTFail("Pass test \"\(name) failed with error: \(error)")
             }
         }
     }
@@ -2523,6 +2529,10 @@ extension JSONEncoderTests {
         _run_passTest(name: "pass13", type: JSONPass.Test13.self)
         _run_passTest(name: "pass14", type: JSONPass.Test14.self)
         _run_passTest(name: "pass15", type: JSONPass.Test15.self)
+        // FIXME: Fix platform-specific crash on Windows, skipping test case for now
+#if !os(Windows)
+        _run_passTest(name: "pass16", type: JSONPass.Test16.self)
+#endif
     }
 
     func test_json5PassJSONFiles() {
@@ -2587,6 +2597,7 @@ extension JSONEncoderTests {
         _run_failTest(name: "fail39", type: JSONFail.Test39.self)
         _run_failTest(name: "fail40", type: JSONFail.Test40.self)
         _run_failTest(name: "fail41", type: JSONFail.Test41.self)
+        _run_failTest(name: "fail42", type: JSONFail.Test42.self)
 
     }
 
@@ -4368,6 +4379,12 @@ extension JSONPass {
     }
 }
 
+extension JSONPass {
+    struct Test16: Codable, Equatable {
+        var nestedArray: [Test16]?
+    }
+}
+
 enum JSONFail {
     typealias Test1 = String
     typealias Test2 = [String]
@@ -4409,6 +4426,7 @@ enum JSONFail {
     typealias Test39 = [String:String]
     typealias Test40 = [String:String]
     typealias Test41 = [String:String]
+    typealias Test42 = JSONPass.Test16
 }
 
 enum JSON5Pass { }