Fixed a problem that caused an error when decoding optional values in arrays.

Author: AmerigoM

Sources/CBORCoding/CBORDecoder.swift

@@ -1020,7 +1020,7 @@ private struct __CBORUnkeyedDecodingContainer: UnkeyedDecodingContainer {
         defer { decoder.codingPath.removeLast() }
 
         let value = container[currentIndex]
-        guard !(value is CBOR.Null) else {
+        guard !(value is CBOR.Null) || (value is CBOR.Null && isOptionalType(type)) else {
             throw DecodingError.valueNotFound(T.self, DecodingError.Context(codingPath: decoder.codingPath + [CBOR.CodingKey(index: currentIndex)], debugDescription: "Expected \(T.self) but found null instead."))
         }
 
@@ -1039,7 +1039,7 @@ private struct __CBORUnkeyedDecodingContainer: UnkeyedDecodingContainer {
         defer { decoder.codingPath.removeLast() }
 
         let value = container[currentIndex]
-        guard !(value is CBOR.Null) else {
+        guard !(value is CBOR.Null) || (value is CBOR.Null && isOptionalType(type)) else {
             throw DecodingError.valueNotFound(T.self, DecodingError.Context(codingPath: decoder.codingPath + [CBOR.CodingKey(index: currentIndex)], debugDescription: "Expected \(T.self) but found null instead."))
         }
 
@@ -1058,7 +1058,7 @@ private struct __CBORUnkeyedDecodingContainer: UnkeyedDecodingContainer {
         defer { decoder.codingPath.removeLast() }
 
         let value = container[currentIndex]
-        guard !(value is CBOR.Null) else {
+        guard !(value is CBOR.Null) || (value is CBOR.Null && isOptionalType(type)) else {
             throw DecodingError.valueNotFound(T.self, DecodingError.Context(codingPath: decoder.codingPath + [CBOR.CodingKey(index: currentIndex)], debugDescription: "Expected \(T.self) but found null instead."))
         }
 
@@ -1077,7 +1077,7 @@ private struct __CBORUnkeyedDecodingContainer: UnkeyedDecodingContainer {
         defer { decoder.codingPath.removeLast() }
 
         let value = container[currentIndex]
-        guard !(value is CBOR.Null) else {
+        guard !(value is CBOR.Null) || (value is CBOR.Null && isOptionalType(type)) else {
             throw DecodingError.valueNotFound(T.self, DecodingError.Context(codingPath: decoder.codingPath + [CBOR.CodingKey(index: currentIndex)], debugDescription: "Expected \(T.self) but found null instead."))
         }
 
@@ -1088,6 +1088,20 @@ private struct __CBORUnkeyedDecodingContainer: UnkeyedDecodingContainer {
     }
 }
 
+// MARK: - Optional Extension
+
+// Protocol to determine if type is optional
+// https://stackoverflow.com/questions/32536420/determine-if-any-type-is-optional
+
+protocol OptionalProtocol {}
+extension Optional: OptionalProtocol {}
+
+extension __CBORUnkeyedDecodingContainer {
+    private func isOptionalType(_ type: Any.Type) -> Bool {
+        return type is OptionalProtocol.Type
+    }
+}
+
 // MARK: - DecodingError Extension
 
 extension DecodingError {

Tests/CBORCodingTests/CBORDecoderTests.swift

@@ -1192,6 +1192,29 @@ class CBORDecoderTests: XCTestCase {
 
         XCTAssertNoThrow(try CBORDecoder().decode(Test2.self, from: convertFromHexString("0xA2616101616202")))
     }
+    
+    func testDecodingNilValuesInArray() throws {
+        let arrayWithNilValues: [UInt?] = [nil, nil]
+        let arrayWithNilCborData = try CBOREncoder().encode(arrayWithNilValues)
+
+        XCTAssertNoThrow(try CBORDecoder().decode([UInt?].self, from: arrayWithNilCborData))
+    }
+
+    func testDecodingNilValuesInArray2() throws {
+        let arrayWithNilValues: [UInt?] = [nil, 2]
+        let arrayWithNilCborData = try CBOREncoder().encode(arrayWithNilValues)
+
+        XCTAssertNoThrow(try CBORDecoder().decode([UInt?].self, from: arrayWithNilCborData))
+    }
+
+    func testDecodingNilValuesInArray3() throws {
+        let arrayWithNilValues: [UInt?] = [nil, 2]
+        let arrayWithNilCborData = try CBOREncoder().encode(arrayWithNilValues)
+
+        let decodedValue = try CBORDecoder().decode([UInt?].self, from: arrayWithNilCborData)
+
+        XCTAssertEqual(decodedValue, [nil, 2])
+    }
 
     // MARK: Private Methods