Implement Data encoding/decoding strategies

Author: lilyball

README.md

@@ -272,6 +272,8 @@ Unless you explicitly state otherwise, any contribution intentionally submitted
 * Add `JSON.Decoder.keyDecodingStrategy`. This is very similar to Swift 4.1's `JSONDecoder.keyDecodingStrategy`, although by default it won't apply to decoding any values of type `JSON` or `JSONObject` (there's another option `applyKeyDecodingStrategyToJSONObject` that controls this).
 * Add `JSON.Encoder.dateEncodingStrategy`. This is very similar to `JSONEncoder.dateEncodingStrategy` except it includes another case for encoding ISO8601-formatted dates with fractional seconds (on Apple platforms).
 * Add `JSON.Decoder.dateDecodingStrategy`. This is very similar to `JSONDecoder.dateDecodingStrategy` except it includes another case for decoding ISO8601-formatted dates with fractional seconds (on Apple platforms).
+* Add `JSON.Encoder.dataEncodingStrategy`. This is identical to `JSONEncoder.dataEncodingStrategy`.
+* Add `JSON.Decoder.dataDecodingStrategy`. This is identical to `JSONDecoder.dataDecodingStrategy`.
 
 #### v3.0.2 (2018-02-21)
 

Sources/Coders/SwiftDecoder.swift

@@ -38,6 +38,9 @@ extension JSON {
         /// The strategy to use in decoding dates. Defaults to `.deferredToDate`.
         public var dateDecodingStrategy: DateDecodingStrategy = .deferredToDate
 
+        /// The strategy to use in decoding binary data. Defaults to `.base64`.
+        public var dataDecodingStrategy: DataDecodingStrategy = .base64
+        
         /// Creates a new, reusable JSON decoder.
         public init() {}
 
@@ -91,6 +94,7 @@ extension JSON {
             data.keyDecodingStrategy = keyDecodingStrategy
             data.applyKeyDecodingStrategyToJSONObject = applyKeyDecodingStrategyToJSONObject
             data.dateDecodingStrategy = dateDecodingStrategy
+            data.dataDecodingStrategy = dataDecodingStrategy
             return try _JSONDecoder(data: data, value: json).decode(type)
         }
     }
@@ -102,6 +106,7 @@ private class DecoderData {
     var keyDecodingStrategy: JSON.Decoder.KeyDecodingStrategy = .useDefaultKeys
     var applyKeyDecodingStrategyToJSONObject = false
     var dateDecodingStrategy: JSON.Decoder.DateDecodingStrategy = .deferredToDate
+    var dataDecodingStrategy: JSON.Decoder.DataDecodingStrategy = .base64
 
     func copy() -> DecoderData {
         let result = DecoderData()
@@ -110,6 +115,7 @@ private class DecoderData {
         result.keyDecodingStrategy = keyDecodingStrategy
         result.applyKeyDecodingStrategyToJSONObject = applyKeyDecodingStrategyToJSONObject
         result.dateDecodingStrategy = dateDecodingStrategy
+        result.dataDecodingStrategy = dataDecodingStrategy
         return result
     }
 }
@@ -364,6 +370,19 @@ extension _JSONDecoder: SingleValueDecodingContainer {
             case .custom(let decode):
                 return try decode(self) as! T
             }
+        case is Data.Type:
+            switch _data.dataDecodingStrategy {
+            case .deferredToData:
+                break
+            case .base64:
+                let str = try wrapTypeMismatch(value.asJSON.getString())
+                guard let data = Data(base64Encoded: str) else {
+                    throw DecodingError.dataCorruptedError(in: self, debugDescription: "Encountered Data is not valid Base64.")
+                }
+                return data as! T
+            case .custom(let decode):
+                return try decode(self) as! T
+            }
         default:
             break
         }
@@ -811,6 +830,18 @@ extension JSON.Decoder {
         /// Decode the `Date` as a custom value decoded by the given closure.
         case custom((_ decoder: Decoder) throws -> Date)
     }
+    
+    /// The strategy to use for decoding `Data` values.
+    public enum DataDecodingStrategy {
+        /// Defer to `Data` for decoding.
+        case deferredToData
+        
+        /// Decode the `Data` from a Base64-encoded string. This is the default strategy.
+        case base64
+        
+        /// Decodes the `Data` as a custom value decoded by the given closure.
+        case custom((_ decoder: Decoder) throws -> Data)
+    }
 }
 
 // MARK: -

Sources/Coders/SwiftEncoder.swift

@@ -201,6 +201,9 @@ extension JSON {
         /// The strategy to use in encoding dates. Defaults to `.deferredToDate`.
         public var dateEncodingStrategy: DateEncodingStrategy = .deferredToDate
 
+        /// The strategy to use in encoding binary data. Defaults to `.base64`.
+        public var dataEncodingStrategy: DataEncodingStrategy = .base64
+        
         /// Creates a new, reusable JSON encoder.
         public init() {}
 
@@ -252,6 +255,7 @@ extension JSON {
             data.keyEncodingStrategy = keyEncodingStrategy
             data.applyKeyEncodingStrategyToJSONObject = applyKeyEncodingStrategyToJSONObject
             data.dateEncodingStrategy = dateEncodingStrategy
+            data.dataEncodingStrategy = dataEncodingStrategy
             let encoder = _JSONEncoder(data: data)
             try encoder.encode(value)
             guard let json = encoder.json else {
@@ -268,6 +272,7 @@ private class EncoderData {
     var keyEncodingStrategy: JSON.Encoder.KeyEncodingStrategy = .useDefaultKeys
     var applyKeyEncodingStrategyToJSONObject = false
     var dateEncodingStrategy: JSON.Encoder.DateEncodingStrategy = .deferredToDate
+    var dataEncodingStrategy: JSON.Encoder.DataEncodingStrategy = .base64
 
     var shouldRekeyJSONObjects: Bool {
         switch keyEncodingStrategy {
@@ -283,6 +288,7 @@ private class EncoderData {
         result.keyEncodingStrategy = keyEncodingStrategy
         result.applyKeyEncodingStrategyToJSONObject = applyKeyEncodingStrategyToJSONObject
         result.dateEncodingStrategy = dateEncodingStrategy
+        result.dataEncodingStrategy = dataEncodingStrategy
         return result
     }
 }
@@ -529,6 +535,19 @@ extension _JSONEncoder: SingleValueEncodingContainer {
                     self.json = .unboxed([:])
                 }
             }
+        case let data as Data:
+            switch _data.dataEncodingStrategy {
+            case .deferredToData:
+                try value.encode(to: self)
+            case .base64:
+                try encode(data.base64EncodedString())
+            case .custom(let f):
+                try f(data, self)
+                if self.value?.isEmpty ?? true {
+                    // the function didn't encode anything
+                    self.json = .unboxed([:])
+                }
+            }
         default:
             try value.encode(to: self)
         }
@@ -953,4 +972,19 @@ extension JSON.Encoder {
         /// an empty object in its place.
         case custom((Date, Encoder) throws -> Void)
     }
+    
+    /// The strategy to use for encoding `Data` values.
+    public enum DataEncodingStrategy {
+        /// Defer to `Data` for choosing an encoding.
+        case deferredToData
+        
+        /// Encode the `Data` as a Base64-encoded string. This is the default strategy.
+        case base64
+        
+        /// Encode the `Data` as a custom value encoded by the given closure.
+        ///
+        /// If the closure fails to encode a value into the given encoder, the encoder will encode
+        /// an empty object in its place.
+        case custom((_ data: Data, _ encoder: Encoder) throws -> Void)
+    }
 }

Tests/PMJSONTests/SwiftDecoderTests.swift

@@ -432,6 +432,38 @@ final class SwiftDecoderTests: XCTestCase {
         let date = try decoder.decode(Date.self, from: 541317080)
         XCTAssertEqual(date, Date(timeIntervalSinceReferenceDate: 541318080))
     }
+    
+    // MARK: - DataDecodingStrategy
+    
+    func testDecodeDataDefaultStrategy() throws {
+        let input = "hello".data(using: .utf8)!
+        let decoder = JSON.Decoder()
+        // don't assume the default format since that's up to Data, just encode it first
+        let json = try JSON.Encoder().encodeAsJSON(input)
+        let data = try decoder.decode(Data.self, from: json)
+        XCTAssertEqual(data, input)
+    }
+    
+    func testDecodeDataBase64() throws {
+        var decoder = JSON.Decoder()
+        decoder.dataDecodingStrategy = .base64
+        let data = try decoder.decode(Data.self, from: "aGVsbG8=" as JSON)
+        XCTAssertEqual(data, "hello".data(using: .utf8)!)
+    }
+    
+    func testDecodeDataCustom() throws {
+        var decoder = JSON.Decoder()
+        decoder.dataDecodingStrategy = .custom({ (decoder) -> Data in
+            let container = try decoder.singleValueContainer()
+            let str = try container.decode(String.self)
+            guard let data = Data(base64Encoded: String(str.reversed())) else {
+                throw DecodingError.dataCorruptedError(in: container, debugDescription: "Could not decode Data.")
+            }
+            return data
+        })
+        let data = try decoder.decode(Data.self, from: "=8GbsVGa" as JSON)
+        XCTAssertEqual(data, "hello".data(using: .utf8)!)
+    }
 }
 
 private extension Date {

Tests/PMJSONTests/SwiftEncoderTests.swift

@@ -811,6 +811,43 @@ final class SwiftEncoderTests: XCTestCase {
         let json = try encoder.encodeAsJSON(Date())
         XCTAssertEqual(json, [:])
     }
+    
+    // MARK: - DataEncodingStrategy
+    
+    func testEncodeDataDefaultStrategy() throws {
+        let input = "hello".data(using: .utf8)!
+        let encoder = JSON.Encoder()
+        // don't assume the default format since that's up to Data, just decode it after
+        let json = try encoder.encodeAsJSON(input)
+        let data = try JSON.Decoder().decode(Data.self, from: json)
+        XCTAssertEqual(data, input)
+    }
+    
+    func testEncodeDataBase64() throws {
+        var encoder = JSON.Encoder()
+        encoder.dataEncodingStrategy = .base64
+        let json = try encoder.encodeAsJSON("hello".data(using: .utf8)!)
+        XCTAssertEqual(json, "aGVsbG8=")
+    }
+    
+    func testEncodeDataCustom() throws {
+        var encoder = JSON.Encoder()
+        encoder.dataEncodingStrategy = .custom({ (data, encoder) in
+            let str = String(data.base64EncodedString().reversed())
+            try str.encode(to: encoder)
+        })
+        let json = try encoder.encodeAsJSON("hello".data(using: .utf8)!)
+        XCTAssertEqual(json, "=8GbsVGa")
+    }
+    
+    func testEncodeDataCustomNoEncode() throws {
+        var encoder = JSON.Encoder()
+        encoder.dataEncodingStrategy = .custom({ (data, encoder) in
+            // do nothing
+        })
+        let json = try encoder.encodeAsJSON("hello".data(using: .utf8)!)
+        XCTAssertEqual(json, [:])
+    }
 }
 
 private extension Date {