Fix unkeyed decoding cursor and colliding custom keys

Sources/Decoder/DictionaryComponentDecoder.swift

@@ -103,10 +103,6 @@ extension DictionaryComponentDecoder {
             return Date(timeIntervalSince1970: try decodePrimitiveValue(from: component, at: codingPath) / 1000.0)
 
         case .iso8601:
-            guard #available(macOS 10.12, iOS 10.0, watchOS 3.0, tvOS 10.0, *) else {
-                fatalError("ISO8601DateFormatter is unavailable on this platform.")
-            }
-
             let formattedDate = try decodePrimitiveValue(of: String.self, from: component, at: codingPath)
 
             guard let date = ISO8601DateFormatter().date(from: formattedDate) else {

Sources/Decoder/DictionaryDecoder.swift

@@ -54,41 +54,33 @@ public final class DictionaryDecoder: Sendable {
 
     // MARK: - Instance Methods
 
-    public func decode<T: Decodable>(
-        _ type: T.Type = T.self,
-        from dictionary: [String: Any]
-    ) throws -> T {
+    private func rootDecoder(for dictionary: [String: Any]) -> DictionarySingleValueDecodingContainer {
         let options = optionsMutex.withLock { $0 }
 
-        let decoder = DictionarySingleValueDecodingContainer(
+        return DictionarySingleValueDecodingContainer(
             component: dictionary,
             options: options,
             userInfo: userInfo,
             codingPath: []
         )
+    }
 
-        return try T(from: decoder)
+    public func decode<T: Decodable>(
+        _ type: T.Type = T.self,
+        from dictionary: [String: Any]
+    ) throws -> T {
+        try T(from: rootDecoder(for: dictionary))
     }
 
     public func decode<T: Decodable>(from dictionary: [String: Any]) throws -> T {
         try decode(T.self, from: dictionary)
     }
 
-    @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
     public func decode<T: DecodableWithConfiguration>(
         _ type: T.Type = T.self,
         from dictionary: [String: Any],
         configuration: T.DecodingConfiguration
     ) throws -> T {
-        let options = optionsMutex.withLock { $0 }
-
-        let decoder = DictionarySingleValueDecodingContainer(
-            component: dictionary,
-            options: options,
-            userInfo: userInfo,
-            codingPath: []
-        )
-
-        return try T(from: decoder, configuration: configuration)
+        try T(from: rootDecoder(for: dictionary), configuration: configuration)
     }
 }

Sources/Decoder/DictionaryKeyedDecodingContainer.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 internal class DictionaryKeyedDecodingContainer<Key: CodingKey>:
     KeyedDecodingContainerProtocol,
     DictionaryComponentDecoder {
@@ -27,12 +25,12 @@ internal class DictionaryKeyedDecodingContainer<Key: CodingKey>:
         case .useDefaultKeys:
             self.components = components
 
-        case let.custom(closure):
-            let componentKeysAndValues = components.map { key, value in
-                (closure(codingPath.appending(AnyCodingKey(key))).stringValue, value)
-            }
+        case let .custom(closure):
+            let componentKeysAndValues = components
+                .sorted { $0.key < $1.key }
+                .map { key, value in (closure(codingPath.appending(AnyCodingKey(key))).stringValue, value) }
 
-            self.components = Dictionary(componentKeysAndValues) { $1 }
+            self.components = Dictionary(componentKeysAndValues) { first, _ in first }
         }
 
         self.options = options

Sources/Decoder/DictionarySingleValueDecodingContainer.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 internal final class DictionarySingleValueDecodingContainer:
     Decoder,
     SingleValueDecodingContainer,

Sources/Decoder/DictionaryUnkeyedDecodingContainer.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 internal final class DictionaryUnkeyedDecodingContainer:
     UnkeyedDecodingContainer,
     DictionaryComponentDecoder {
@@ -41,7 +39,8 @@ internal final class DictionaryUnkeyedDecodingContainer:
 
     // MARK: - Instance Methods
 
-    private func popNextComponent() throws -> Any? {
+    @inline(__always)
+    private func peekNextComponent() throws -> Any? {
         guard currentIndex < components.count else {
             let errorContext = DecodingError.Context(
                 codingPath: currentCodingPath,
@@ -51,95 +50,112 @@ internal final class DictionaryUnkeyedDecodingContainer:
             throw DecodingError.valueNotFound(Any.self, errorContext)
         }
 
-        defer {
-            currentIndex += 1
-        }
-
         return components[currentIndex]
     }
 
+    @inline(__always)
+    private func decodeNextComponent<T>(
+        _ decodeComponent: (_ component: Any?, _ codingPath: [CodingKey]) throws -> T
+    ) throws -> T {
+        let value = try decodeComponent(try peekNextComponent(), currentCodingPath)
+
+        currentIndex += 1
+
+        return value
+    }
+
+    private func superDecoder(for component: Any?, at codingPath: [CodingKey]) -> Decoder {
+        DictionarySingleValueDecodingContainer(
+            component: component,
+            options: options,
+            userInfo: userInfo,
+            codingPath: codingPath
+        )
+    }
+
     // MARK: - UnkeyedDecodingContainer
 
     internal func decodeNil() throws -> Bool {
-        decodeNilComponent(from: try popNextComponent())
+        guard decodeNilComponent(from: try peekNextComponent()) else {
+            return false
+        }
+
+        currentIndex += 1
+
+        return true
     }
 
     internal func decode(_ type: Bool.Type) throws -> Bool {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: Int.Type) throws -> Int {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: Int8.Type) throws -> Int8 {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: Int16.Type) throws -> Int16 {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: Int32.Type) throws -> Int32 {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: Int64.Type) throws -> Int64 {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: UInt.Type) throws -> UInt {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: UInt8.Type) throws -> UInt8 {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: UInt16.Type) throws -> UInt16 {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: UInt32.Type) throws -> UInt32 {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: UInt64.Type) throws -> UInt64 {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: Double.Type) throws -> Double {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: Float.Type) throws -> Float {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode(_ type: String.Type) throws -> String {
-        try decodeComponentValue(from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(from: $0, at: $1) }
     }
 
     internal func decode<T: Decodable>(_ type: T.Type) throws -> T {
-        try decodeComponentValue(of: type, from: try popNextComponent(), at: currentCodingPath)
+        try decodeNextComponent { try decodeComponentValue(of: type, from: $0, at: $1) }
     }
 
     internal func nestedContainer<NestedKey: CodingKey>(
         keyedBy keyType: NestedKey.Type
     ) throws -> KeyedDecodingContainer<NestedKey> {
-        try superDecoder().container(keyedBy: keyType)
+        try decodeNextComponent { try superDecoder(for: $0, at: $1).container(keyedBy: keyType) }
     }
 
     internal func nestedUnkeyedContainer() throws -> UnkeyedDecodingContainer {
-        try superDecoder().unkeyedContainer()
+        try decodeNextComponent { try superDecoder(for: $0, at: $1).unkeyedContainer() }
     }
 
     internal func superDecoder() throws -> Decoder {
-        DictionarySingleValueDecodingContainer(
-            component: try popNextComponent(),
-            options: options,
-            userInfo: userInfo,
-            codingPath: currentCodingPath
-        )
+        try decodeNextComponent { superDecoder(for: $0, at: $1) }
     }
 }

Sources/Decoder/Options/DictionaryDateDecodingStrategy.swift

@@ -15,7 +15,6 @@ public enum DictionaryDateDecodingStrategy: Sendable {
     case millisecondsSince1970
 
     /// The strategy that formats dates according to the ISO 8601 standard.
-    @available(macOS 10.12, iOS 10.0, watchOS 3.0, tvOS 10.0, *)
     case iso8601
 
     /// The strategy that defers formatting settings to a supplied date formatter.

Sources/Decoder/Options/DictionaryDecodingOptions.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 internal struct DictionaryDecodingOptions {
 
     // MARK: - Instance Properties

Sources/Decoder/Options/DictionaryKeyDecodingStrategy.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 /// The values that determine how to decode a type’s coding keys from Dictionary keys.
 public enum DictionaryKeyDecodingStrategy: Sendable {
 
@@ -9,5 +7,8 @@ public enum DictionaryKeyDecodingStrategy: Sendable {
     case useDefaultKeys
 
     /// A key decoding strategy defined by the closure you supply.
+    ///
+    /// If several keys are converted to the same key,
+    /// the value of the lexicographically smallest original key is used.
     case custom(@Sendable (_ codingPath: [CodingKey]) -> CodingKey)
 }

Sources/Decoder/Options/DictionaryNonConformingFloatDecodingStrategy.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 /// The strategies for encoding nonconforming floating-point numbers,
 /// also known as IEEE 754 exceptional values.
 public enum DictionaryNonConformingFloatDecodingStrategy: Sendable {

Sources/Encoder/DictionaryAnyKeyedEncodingContainer.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 internal final class DictionaryAnyKeyedEncodingContainer: DictionaryComponentContainer {
 
     // MARK: - Instance Properties

Sources/Encoder/DictionaryComponent.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 internal indirect enum DictionaryComponent {
 
     // MARK: - Enumeration Cases

Sources/Encoder/DictionaryComponentContainer.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 internal protocol DictionaryComponentContainer {
 
     // MARK: - Instance Methods

Sources/Encoder/DictionaryComponentEncoder.swift

@@ -72,10 +72,6 @@ extension DictionaryComponentEncoder {
             return encodePrimitiveValue(date.timeIntervalSince1970, at: codingPath)
 
         case .iso8601:
-            guard #available(macOS 10.12, iOS 10.0, watchOS 3.0, tvOS 10.0, *) else {
-                fatalError("ISO8601DateFormatter is unavailable on this platform.")
-            }
-
             let formattedDate = ISO8601DateFormatter.string(
                 from: date,
                 timeZone: .iso8601TimeZone,
@@ -250,6 +246,6 @@ extension EncodingError {
             Use DictionaryNonConformingFloatEncodingStrategy.convertToString to specify how the value should be encoded.
             """
 
-        return .invalidValue(value, EncodingError.Context(codingPath: codingPath, debugDescription: debugDescription))
+        return .invalidValue(value, Context(codingPath: codingPath, debugDescription: debugDescription))
     }
 }

Sources/Encoder/DictionaryEncoder.swift

@@ -61,7 +61,10 @@ public final class DictionaryEncoder: Sendable {
 
     // MARK: - Instance Methods
 
-    public func encode<T: Encodable>(_ value: T) throws -> [String: Sendable] {
+    private func encodeRootValue<T>(
+        _ value: T,
+        encoding: (_ encoder: Encoder) throws -> Void
+    ) throws -> [String: Sendable] {
         let options = optionsMutex.withLock { $0 }
 
         let encoder = DictionarySingleValueEncodingContainer(
@@ -70,7 +73,7 @@ public final class DictionaryEncoder: Sendable {
             codingPath: []
         )
 
-        try value.encode(to: encoder)
+        try encoding(encoder)
 
         guard let dictionary = encoder.resolveValue() as? [String: Sendable] else {
             let errorContext = EncodingError.Context(
@@ -84,30 +87,18 @@ public final class DictionaryEncoder: Sendable {
         return dictionary
     }
 
-    @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
+    public func encode<T: Encodable>(_ value: T) throws -> [String: Sendable] {
+        try encodeRootValue(value) { encoder in
+            try value.encode(to: encoder)
+        }
+    }
+
     public func encode<T: EncodableWithConfiguration>(
         _ value: T,
         configuration: T.EncodingConfiguration
     ) throws -> [String: Sendable] {
-        let options = optionsMutex.withLock { $0 }
-
-        let encoder = DictionarySingleValueEncodingContainer(
-            options: options,
-            userInfo: userInfo,
-            codingPath: []
-        )
-
-        try value.encode(to: encoder, configuration: configuration)
-
-        guard let dictionary = encoder.resolveValue() as? [String: Sendable] else {
-            let errorContext = EncodingError.Context(
-                codingPath: [],
-                debugDescription: "Root component cannot be encoded in Dictionary"
-            )
-
-            throw EncodingError.invalidValue(value, errorContext)
+        try encodeRootValue(value) { encoder in
+            try value.encode(to: encoder, configuration: configuration)
         }
-
-        return dictionary
     }
 }

Sources/Encoder/DictionaryKeyedEncodingContainer.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 internal final class DictionaryKeyedEncodingContainer<Key: CodingKey>:
     KeyedEncodingContainerProtocol,
     DictionaryComponentEncoder {

Sources/Encoder/DictionarySingleValueEncodingContainer.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 internal final class DictionarySingleValueEncodingContainer:
     Encoder,
     SingleValueEncodingContainer,

Sources/Encoder/DictionaryUnkeyedEncodingContainer.swift

@@ -1,5 +1,3 @@
-import Foundation
-
 internal final class DictionaryUnkeyedEncodingContainer:
     UnkeyedEncodingContainer,
     DictionaryComponentContainer,