[Enhancement] Lossy codable list property wrapper (#19)

This PR contains the work done to implement the `LossyCodableList` struct and property wrapper, which is used in lossy decoding/encoding processes.

Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Reviewed-on: https://repo.rock-n-code.com/rock-n-code/swift-libs/pulls/19

Sources/Core/Property Wrappers/LossyCodableList.swift

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+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftLibs open source project
+//
+// Copyright (c) 2023 Röck+Cöde VoF. and the SwiftLibs project authors
+// Licensed under the EUPL 1.2 or later.
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftLibs project authors
+//
+//===----------------------------------------------------------------------===//
+
+@propertyWrapper
+/// This property wrapper provides a generic type that acts as a thin wrapper around an array of `Elements` instances to allow a lossy decoding and or encoding process.
+public struct LossyCodableList<Element> {
+
+    // MARK: Properties
+
+    private var elements: [Element]
+
+    /// Provides read/write access to the array of `Element` instances.
+    public var wrappedValue: [Element] {
+        get { elements }
+        set { elements = newValue }
+    }
+
+    // MARK: Initialisers
+
+    /// Initialises this property wrapper.
+    public init() {
+        self.elements = []
+    }
+
+}
+
+// MARK: - Decodable
+
+extension LossyCodableList: Decodable where Element: Decodable {
+
+    // MARK: Initialisers
+
+    /// Initialises the struct with a lossy decoder.
+    /// - Parameter decoder: The decoder to use for the lossy decoder process.
+    public init(from decoder: Decoder) throws {
+        let container = try decoder.singleValueContainer()
+        let wrappers = try container.decode([ElementWrapper].self)
+
+        self.elements = wrappers.compactMap(\.element)
+    }
+
+}
+
+// MARK: - Encodable
+
+extension LossyCodableList: Encodable where Element: Encodable {
+
+    // MARK: Functions
+
+    /// Encodes an array of `Element` instances loosely.
+    /// - Parameter encoder: The encoder to use for the lossy encoding process.
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.unkeyedContainer()
+
+        elements.forEach { element in
+            try? container.encode(element)
+        }
+    }
+
+}
+
+// MARK: - Structs
+
+private extension LossyCodableList where Element: Decodable {
+    struct ElementWrapper: Decodable {
+
+        // MARK: Properties
+
+        var element: Element?
+
+        // MARK: Initialisers
+
+        init(from decoder: Decoder) throws {
+            let container = try decoder.singleValueContainer()
+
+            self.element = try? container.decode(Element.self)
+        }
+
+    }
+}

Tests/Core/Cases/Property Wrappers/LossyCodableList+DecodableTests.swift

@@ -0,0 +1,75 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftLibs open source project
+//
+// Copyright (c) 2023 Röck+Cöde VoF. and the SwiftLibs project authors
+// Licensed under the EUPL 1.2 or later.
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftLibs project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Core
+import Foundation
+import XCTest
+
+final class LossyCodableList_DecodableTests: XCTestCase {
+
+    // MARK: Properties
+
+    private let decoder = JSONDecoder()
+
+    private var dataToDecode: Data!
+    private var decodedList: TestCodableList!
+
+    // MARK: Tests
+
+    func test_decode_whenAllDataIsComplete() throws {
+        // GIVEN
+        dataToDecode = .Seed.itemsWithAllKeysHavingIntValues
+
+        // WHEN
+        decodedList = try decoder.decode(TestCodableList.self, from: dataToDecode)
+
+        // THEN
+        XCTAssertNotNil(decodedList)
+        XCTAssertTrue(decodedList.items.isNotEmpty)
+        XCTAssertEqual(decodedList.items, [
+            .init(key: "One", value: 1),
+            .init(key: "Two", value: 2),
+            .init(key: "Three", value: 3),
+            .init(key: "Four", value: 4)
+        ])
+    }
+
+    func test_decode_whenSomeDataHasNil() throws {
+        // GIVEN
+        dataToDecode = .Seed.itemsWithSomeKeysAndValuesAreNil
+
+        // WHEN
+        decodedList = try decoder.decode(TestCodableList.self, from: dataToDecode)
+
+        // THEN
+        XCTAssertNotNil(decodedList)
+        XCTAssertTrue(decodedList.items.isNotEmpty)
+        XCTAssertEqual(decodedList.items, [
+            .init(key: "One", value: 1),
+            .init(key: "Three", value: 3)
+        ])
+    }
+
+    func test_decode_whenAllDataHasNil() throws {
+        // GIVEN
+        dataToDecode = .Seed.itemsWithAllKeysAndValuesAreNil
+
+        // WHEN
+        decodedList = try decoder.decode(TestCodableList.self, from: dataToDecode)
+
+        // THEN
+        XCTAssertNotNil(decodedList)
+        XCTAssertTrue(decodedList.items.isEmpty)
+        XCTAssertEqual(decodedList.items, [])
+    }
+
+}

Tests/Core/Cases/Property Wrappers/LossyCodableList+EncodableTests.swift

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+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftLibs open source project
+//
+// Copyright (c) 2023 Röck+Cöde VoF. and the SwiftLibs project authors
+// Licensed under the EUPL 1.2 or later.
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftLibs project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+import XCTest
+
+@testable import Core
+
+final class LossyCodableList_EncodableTests: XCTestCase {
+
+    // MARK: Properties
+
+    private let decoder = JSONDecoder()
+    private let encoder = JSONEncoder()
+
+    private var dataToDecode: Data!
+    private var encodedData: Data!
+    private var list: TestCodableList!
+
+    // MARK: Setup
+
+    override func setUpWithError() throws {
+        // This setting is used to guarantee that the properties of the model are being generated by sorted keys order.
+        encoder.outputFormatting = .sortedKeys
+    }
+
+    // MARK: Tests
+
+    func test_encode_whenAllKeysHaveIntValues() throws {
+        // GIVEN
+        dataToDecode = .Seed.itemsWithAllKeysHavingIntValues
+        list = try decoder.decode(TestCodableList.self, from: dataToDecode)
+
+        // WHEN
+        encodedData = try encoder.encode(list)
+
+        // THEN
+        XCTAssertNotNil(encodedData)
+        XCTAssertTrue(encodedData.isNotEmpty)
+        XCTAssertEqual(encodedData, .Result.allItemsNotFilteredOut)
+    }
+
+    func test_encode_whenSomeKeysAndValuesAreNil() throws {
+        // GIVEN
+        dataToDecode = .Seed.itemsWithSomeKeysAndValuesAreNil
+        list = try decoder.decode(TestCodableList.self, from: dataToDecode)
+
+        // WHEN
+        encodedData = try encoder.encode(list)
+
+        // THEN
+        XCTAssertNotNil(encodedData)
+        XCTAssertTrue(encodedData.isNotEmpty)
+        XCTAssertEqual(encodedData, .Result.someItemsFilteredOut)
+    }
+
+    func test_encode_whenAllKeysAndValuesAreNil() throws {
+        // GIVEN
+        dataToDecode = .Seed.itemsWithAllKeysAndValuesAreNil
+        list = try decoder.decode(TestCodableList.self, from: dataToDecode)
+
+        // WHEN
+        encodedData = try encoder.encode(list)
+
+        // THEN
+        XCTAssertNotNil(encodedData)
+        XCTAssertTrue(encodedData.isNotEmpty)
+        XCTAssertEqual(encodedData, .Result.allItemsFilteredOut)
+    }
+
+}

Tests/Core/Helpers/Extensions/Data+Result.swift

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftLibs open source project
+//
+// Copyright (c) 2023 Röck+Cöde VoF. and the SwiftLibs project authors
+// Licensed under the EUPL 1.2 or later.
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftLibs project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+extension Data {
+    enum Result {
+        static let allItemsNotFilteredOut = String.Result.allItemsNotFilteredOut.data(using: .utf8)
+        static let someItemsFilteredOut = String.Result.someItemsFilteredOut.data(using: .utf8)
+        static let allItemsFilteredOut = String.Result.allItemsFilteredOut.data(using: .utf8)
+    }
+}

Tests/Core/Helpers/Extensions/Data+Seed.swift

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftLibs open source project
+//
+// Copyright (c) 2023 Röck+Cöde VoF. and the SwiftLibs project authors
+// Licensed under the EUPL 1.2 or later.
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftLibs project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+extension Data {
+    enum Seed {
+        static let itemsWithAllKeysHavingIntValues = String.Seed.itemsWithAllKeysHavingIntValues.data(using: .utf8)
+        static let itemsWithSomeKeysAndValuesAreNil = String.Seed.itemsWithSomeKeysAndValuesAreNil.data(using: .utf8)
+        static let itemsWithAllKeysAndValuesAreNil = String.Seed.itemsWithAllKeysAndValuesAreNil.data(using: .utf8)
+    }
+}

Tests/Core/Helpers/Extensions/String+Result.swift

@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftLibs open source project
+//
+// Copyright (c) 2023 Röck+Cöde VoF. and the SwiftLibs project authors
+// Licensed under the EUPL 1.2 or later.
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftLibs project authors
+//
+//===----------------------------------------------------------------------===//
+
+extension String {
+    enum Result {
+        static let allItemsNotFilteredOut = "{\"items\":[{\"key\":\"One\",\"value\":1},{\"key\":\"Two\",\"value\":2},{\"key\":\"Three\",\"value\":3},{\"key\":\"Four\",\"value\":4}]}"
+        static let someItemsFilteredOut = "{\"items\":[{\"key\":\"One\",\"value\":1},{\"key\":\"Three\",\"value\":3}]}"
+        static let allItemsFilteredOut = "{\"items\":[]}"
+    }
+}

Tests/Core/Helpers/Extensions/String+Seed.swift

@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftLibs open source project
+//
+// Copyright (c) 2023 Röck+Cöde VoF. and the SwiftLibs project authors
+// Licensed under the EUPL 1.2 or later.
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftLibs project authors
+//
+//===----------------------------------------------------------------------===//
+
+extension String {
+    enum Seed {
+        static let itemsWithAllKeysHavingIntValues = "{\"items\":[{\"key\":\"One\",\"value\":1},{\"key\":\"Two\",\"value\":2},{\"key\":\"Three\",\"value\":3},{\"key\":\"Four\",\"value\":4}]}"
+        static let itemsWithSomeKeysAndValuesAreNil = "{\"items\":[{\"key\":\"One\",\"value\":1},{\"key\":\"Two\",\"value\":null},{\"key\":\"Three\",\"value\":3},{\"key\":null,\"value\":4}]}"
+        static let itemsWithAllKeysAndValuesAreNil = "{\"items\":[{\"key\":\"One\",\"value\":null},{\"key\":null,\"value\":2},{\"key\":\"Three\",\"value\":null},{\"key\":null,\"value\":4}]}"
+    }
+}

Tests/Core/Helpers/Models/TestCodable.swift

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftLibs open source project
+//
+// Copyright (c) 2023 Röck+Cöde VoF. and the SwiftLibs project authors
+// Licensed under the EUPL 1.2 or later.
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftLibs project authors
+//
+//===----------------------------------------------------------------------===//
+
+struct TestCodable: Codable, Equatable {
+    let key: String
+    let value: Int
+}
+
+// MARK: - Initialisers
+
+extension TestCodable {
+    init?(
+        key: String? = nil,
+        value: Int? = nil
+    ) {
+        guard let key, let value else { return nil }
+
+        self.key = key
+        self.value = value
+    }
+}

Tests/Core/Helpers/Models/TestCodableList.swift

@@ -0,0 +1,17 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftLibs open source project
+//
+// Copyright (c) 2023 Röck+Cöde VoF. and the SwiftLibs project authors
+// Licensed under the EUPL 1.2 or later.
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftLibs project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Core
+
+struct TestCodableList: Codable {
+    @LossyCodableList var items: [TestCodable]
+}