├── .gitignore ├── LICENSE ├── Package.swift ├── README.md ├── Sources ├── ModifiedCopy │ └── ModifiedCopy.swift ├── ModifiedCopyClient │ └── main.swift └── ModifiedCopyMacros │ └── ModifiedCopyMacro.swift └── Tests └── ModifiedCopyTests └── ModifiedCopyTests.swift /.gitignore: -------------------------------------------------------------------------------- 1 | # Xcode 2 | # 3 | # gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore 4 | 5 | ## User settings 6 | xcuserdata/ 7 | 8 | ## compatibility with Xcode 8 and earlier (ignoring not required starting Xcode 9) 9 | *.xcscmblueprint 10 | *.xccheckout 11 | 12 | ## compatibility with Xcode 3 and earlier (ignoring not required starting Xcode 4) 13 | build/ 14 | DerivedData/ 15 | *.moved-aside 16 | *.pbxuser 17 | !default.pbxuser 18 | *.mode1v3 19 | !default.mode1v3 20 | *.mode2v3 21 | !default.mode2v3 22 | *.perspectivev3 23 | !default.perspectivev3 24 | 25 | ## Obj-C/Swift specific 26 | *.hmap 27 | 28 | ## App packaging 29 | *.ipa 30 | *.dSYM.zip 31 | *.dSYM 32 | 33 | ## Playgrounds 34 | timeline.xctimeline 35 | playground.xcworkspace 36 | 37 | # Swift Package Manager 38 | # 39 | # Add this line if you want to avoid checking in source code from Swift Package Manager dependencies. 40 | # Packages/ 41 | # Package.pins 42 | # Package.resolved 43 | # *.xcodeproj 44 | # 45 | # Xcode automatically generates this directory with a .xcworkspacedata file and xcuserdata 46 | # hence it is not needed unless you have added a package configuration file to your project 47 | # .swiftpm 48 | 49 | .build/ 50 | 51 | # CocoaPods 52 | # 53 | # We recommend against adding the Pods directory to your .gitignore. However 54 | # you should judge for yourself, the pros and cons are mentioned at: 55 | # https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control 56 | # 57 | # Pods/ 58 | # 59 | # Add this line if you want to avoid checking in source code from the Xcode workspace 60 | # *.xcworkspace 61 | 62 | # Carthage 63 | # 64 | # Add this line if you want to avoid checking in source code from Carthage dependencies. 65 | # Carthage/Checkouts 66 | 67 | Carthage/Build/ 68 | 69 | # Accio dependency management 70 | Dependencies/ 71 | .accio/ 72 | 73 | # fastlane 74 | # 75 | # It is recommended to not store the screenshots in the git repo. 76 | # Instead, use fastlane to re-generate the screenshots whenever they are needed. 77 | # For more information about the recommended setup visit: 78 | # https://docs.fastlane.tools/best-practices/source-control/#source-control 79 | 80 | fastlane/report.xml 81 | fastlane/Preview.html 82 | fastlane/screenshots/**/*.png 83 | fastlane/test_output 84 | 85 | # Code Injection 86 | # 87 | # After new code Injection tools there's a generated folder /iOSInjectionProject 88 | # https://github.com/johnno1962/injectionforxcode 89 | 90 | iOSInjectionProject/ 91 | .swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata 92 | Package.resolved 93 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | MIT License 2 | 3 | Copyright (c) 2023 Wilhelm Oks 4 | 5 | Permission is hereby granted, free of charge, to any person obtaining a copy 6 | of this software and associated documentation files (the "Software"), to deal 7 | in the Software without restriction, including without limitation the rights 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 9 | copies of the Software, and to permit persons to whom the Software is 10 | furnished to do so, subject to the following conditions: 11 | 12 | The above copyright notice and this permission notice shall be included in all 13 | copies or substantial portions of the Software. 14 | 15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 21 | SOFTWARE. 22 | -------------------------------------------------------------------------------- /Package.swift: -------------------------------------------------------------------------------- 1 | // swift-tools-version: 5.9 2 | // The swift-tools-version declares the minimum version of Swift required to build this package. 3 | 4 | import PackageDescription 5 | import CompilerPluginSupport 6 | 7 | let package = Package( 8 | name: "ModifiedCopy", 9 | platforms: [.macOS(.v10_15), .iOS(.v13), .tvOS(.v13), .watchOS(.v6), .macCatalyst(.v13)], 10 | products: [ 11 | // Products define the executables and libraries a package produces, making them visible to other packages. 12 | .library( 13 | name: "ModifiedCopy", 14 | targets: ["ModifiedCopy"] 15 | ), 16 | .executable( 17 | name: "ModifiedCopyClient", 18 | targets: ["ModifiedCopyClient"] 19 | ), 20 | ], 21 | dependencies: [ 22 | // Depend on the latest Swift 5.9 prerelease of SwiftSyntax 23 | .package(url: "https://github.com/swiftlang/swift-syntax.git", from: "509.1.1"), 24 | ], 25 | targets: [ 26 | // Targets are the basic building blocks of a package, defining a module or a test suite. 27 | // Targets can depend on other targets in this package and products from dependencies. 28 | // Macro implementation that performs the source transformation of a macro. 29 | .macro( 30 | name: "ModifiedCopyMacros", 31 | dependencies: [ 32 | .product(name: "SwiftSyntaxMacros", package: "swift-syntax"), 33 | .product(name: "SwiftCompilerPlugin", package: "swift-syntax") 34 | ] 35 | ), 36 | 37 | // Library that exposes a macro as part of its API, which is used in client programs. 38 | .target(name: "ModifiedCopy", dependencies: ["ModifiedCopyMacros"]), 39 | 40 | // A client of the library, which is able to use the macro in its own code. 41 | .executableTarget(name: "ModifiedCopyClient", dependencies: ["ModifiedCopy"]), 42 | 43 | // A test target used to develop the macro implementation. 44 | .testTarget( 45 | name: "ModifiedCopyTests", 46 | dependencies: [ 47 | "ModifiedCopyMacros", 48 | .product(name: "SwiftSyntaxMacrosTestSupport", package: "swift-syntax"), 49 | ] 50 | ), 51 | ] 52 | ) 53 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 |

2 | 3 | 4 | Swift Package Manager 5 | 6 | Platforms: macOS, iOS, tvOS, watchOS, Linux 7 |

8 | 9 | # ModifiedCopyMacro 10 | A Swift macro for making inline copies of a struct by modifying a property.
11 | The syntax is similar to Kotlin's copy function for data classes: https://kotlinlang.org/docs/data-classes.html#copying 12 | 13 | ## Usage 14 | 15 | Apply the `@Copyable` macro to a struct: 16 | 17 | ```swift 18 | @Copyable 19 | struct Person { 20 | let name: String 21 | var age: Int 22 | } 23 | ``` 24 | 25 | and it will add a copy function for each stored property and constant: 26 | ```swift 27 | struct Person { 28 | let name: String 29 | var age: Int 30 | 31 | /// Returns a copy of the caller whose value for `name` is different. 32 | func copy(name: String) -> Self { 33 | .init(name: name, age: age) 34 | } 35 | 36 | /// Returns a copy of the caller whose value for `age` is different. 37 | func copy(age: Int) -> Self { 38 | .init(name: name, age: age) 39 | } 40 | } 41 | ``` 42 | 43 | ## Capabilities, Limitations and Design Choices 44 | 45 | ### Chains for multiple changes 46 | 47 | To make a copy of a struct and modify multiple properties, you can chain the `copy` calls like this:
48 | `Person(name: "Walter White", age: 50).copy(age: 52).copy(name: "Heisenberg")`
49 | 50 | This is different than Kotlin's version of `copy`, which allows multiple parameters to pass in a single call.
51 | It's not possible to implement it like that in Swift because it's not possible to have default values for parameters which refer to the current values of the properties of the struct (or class).
52 | And we also can't use nil as a marker for the old/current value, because nil might be a valid new value that we want the property to set to when we make a copy.
53 | There might be a way that I'm not aware of, to still make it possible. So if you know how to do it, please let me know.
54 | 55 | #### CopyableCombi 56 | 57 | With version 2.1.0, the separate macro CopyableCombi was introduced, which generates copy functions with all combinations of parameters. 58 | This solution has the disadvantage that the number of generated functions can become large quickly, but it provides an API which is more similar to Kotlin's copy function. 59 | 60 | ### Stored properties and constants 61 | 62 | A copy function will be generated for each stored property (`var`) and each constant (`let`) of the struct.
63 | The macro recognizes computed properties by checking if they have `get` or `set` accessors.
64 | 65 | ### Only for struct 66 | 67 | This macro works only for structs.
68 | It doesn't make sense for enums because enums can't have stored properties.
69 | Classes and actors have reference semantics and I don't want this library to provide a copy function for reference types. I just want to augment the natural copy capability of structs with modified properties.
70 | This macro emits a Diagnostic Message when you try to apply it to anything but a struct.
71 | 72 | ### Only with default init 73 | 74 | The generated copy functions produce the copies by calling the synthesized default initializer.
75 | So, if you provide a custom initializer, no default initializer will be synthesized and the copy functions won't work.
76 | You can still have synthesized default initializers if you define your custom initializers in an extension.
77 | 78 | ### No struct extensions 79 | 80 | You can't apply this macro on an extension of a struct.
81 | This seems to be a limitation of the macro system.
82 | If you know how to make it possible, please let me know :) 83 | 84 | ## Installation 85 | 86 | Macros are a new language feature of Swift 5.9 and it will only work in Xcode 15 and later. 87 | 88 | Add the url `https://github.com/WilhelmOks/ModifiedCopyMacro.git` as a Swift Package to your project. 89 | 90 | When prompted, select the Package Product `ModifiedCopy` (Kind: Library) to add to your target. 91 | 92 | Make a clean build. 93 | 94 | `import ModifiedCopy` in the file where you want to attach the `@Copyable` macro. 95 | -------------------------------------------------------------------------------- /Sources/ModifiedCopy/ModifiedCopy.swift: -------------------------------------------------------------------------------- 1 | // The Swift Programming Language 2 | // https://docs.swift.org/swift-book 3 | 4 | /// A macro that adds a `copy` function to a struct for each stored property that the struct contains. 5 | /// Each `copy` function returns a copy of the struct that the macro is attached on, but one property can be set to a differnet value. 6 | @attached(member, names: named(copy)) 7 | public macro Copyable() = #externalMacro(module: "ModifiedCopyMacros", type: "ModifiedCopyMacro") 8 | 9 | @attached(member, names: named(copy)) 10 | public macro CopyableCombi() = #externalMacro(module: "ModifiedCopyMacros", type: "ModifiedCopyCombiMacro") 11 | -------------------------------------------------------------------------------- /Sources/ModifiedCopyClient/main.swift: -------------------------------------------------------------------------------- 1 | import ModifiedCopy 2 | 3 | @Copyable 4 | public struct Person { 5 | private(set) var name: String 6 | 7 | let age: Int 8 | 9 | private var favoriteColor: String 10 | 11 | /// This should not generate a copy function because it's not a stored property. 12 | var fullName: String { 13 | get { 14 | name 15 | } 16 | set { 17 | name = newValue 18 | } 19 | } 20 | 21 | /// This should not generate a copy function because it's not a stored property. 22 | var uppercasedName: String { 23 | name.uppercased() 24 | } 25 | 26 | var nickName: String? = "Bobby Tables" { 27 | didSet { 28 | print("nickName changed to \(nickName ?? "(nil)")") 29 | } 30 | } 31 | 32 | init(name: String, age: Int, favoriteColor: String, nickName: String? = nil) { 33 | self.name = name 34 | self.age = age 35 | self.favoriteColor = favoriteColor 36 | self.nickName = nickName 37 | } 38 | } 39 | 40 | print("Person copy with new age: \(Person(name: "Hank", age: 50, favoriteColor: "pink", nickName: "Hanky").copy(age: 42).age)") 41 | 42 | @CopyableCombi 43 | struct Song { 44 | let title: String 45 | let year: Int 46 | //let isFavorite: Bool 47 | //let rating: Double 48 | } 49 | -------------------------------------------------------------------------------- /Sources/ModifiedCopyMacros/ModifiedCopyMacro.swift: -------------------------------------------------------------------------------- 1 | import SwiftCompilerPlugin 2 | import Foundation 3 | import SwiftSyntax 4 | import SwiftSyntaxBuilder 5 | import SwiftSyntaxMacros 6 | import SwiftDiagnostics 7 | 8 | enum ModifiedCopyDiagnostic: DiagnosticMessage { 9 | case notAStruct 10 | case propertyTypeProblem(PatternBindingListSyntax.Element) 11 | 12 | var severity: DiagnosticSeverity { 13 | switch self { 14 | case .notAStruct: .error 15 | case .propertyTypeProblem: .warning 16 | } 17 | } 18 | 19 | var message: String { 20 | switch self { 21 | case .notAStruct: 22 | "'@Copyable' can only be applied to a 'struct'" 23 | case .propertyTypeProblem(let binding): 24 | "Type error for property '\(binding.pattern)': \(binding)" 25 | } 26 | } 27 | 28 | var diagnosticID: MessageID { 29 | switch self { 30 | case .notAStruct: 31 | .init(domain: "ModifiedCopyMacros", id: "notAStruct") 32 | case .propertyTypeProblem(let binding): 33 | .init(domain: "ModifiedCopyMacros", id: "propertyTypeProblem(\(binding.pattern))") 34 | } 35 | } 36 | } 37 | 38 | public struct ModifiedCopyMacro: MemberMacro { 39 | public static func expansion( 40 | of node: AttributeSyntax, 41 | providingMembersOf declaration: some DeclGroupSyntax, 42 | in context: some MacroExpansionContext 43 | ) throws -> [DeclSyntax] { 44 | guard let structDeclSyntax = declaration as? StructDeclSyntax else { 45 | let diagnostic = Diagnostic(node: Syntax(node), message: ModifiedCopyDiagnostic.notAStruct) 46 | context.diagnose(diagnostic) 47 | return [] 48 | } 49 | 50 | let structVisibility = structDeclSyntax.modifiers.visibilityText() ?? "internal" 51 | 52 | let variables = structDeclSyntax.memberBlock.members.compactMap { $0.decl.as(VariableDeclSyntax.self) } 53 | 54 | let bindings = variables.flatMap(\.bindings).filter { accessorIsAllowed($0.accessorBlock?.accessors) } 55 | 56 | return variables.flatMap { variable in 57 | let variableVisibility = variable.modifiers.visibilityText() ?? structVisibility 58 | 59 | return variable.bindings 60 | .filter { accessorIsAllowed($0.accessorBlock?.accessors) } 61 | .compactMap { binding -> DeclSyntax? in 62 | let propertyName = binding.pattern 63 | guard let typeName = binding.typeAnnotation?.type else { 64 | let diagnostic = Diagnostic(node: Syntax(node), message: ModifiedCopyDiagnostic.propertyTypeProblem(binding)) 65 | context.diagnose(diagnostic) 66 | return nil 67 | } 68 | 69 | 70 | return """ 71 | /// Returns a copy of the caller whose value for `\(propertyName)` is different. 72 | \(raw: variableVisibility) func copy(\(propertyName): \(typeName.trimmed)) -> Self { 73 | .init(\(raw: bindings.map { "\($0.pattern): \($0.pattern)" }.joined(separator: ", "))) 74 | } 75 | """ 76 | } 77 | } 78 | } 79 | } 80 | 81 | public struct ModifiedCopyCombiMacro: MemberMacro { 82 | public static func expansion( 83 | of node: AttributeSyntax, 84 | providingMembersOf declaration: some DeclGroupSyntax, 85 | in context: some MacroExpansionContext 86 | ) throws -> [DeclSyntax] { 87 | guard let structDeclSyntax = declaration as? StructDeclSyntax else { 88 | let diagnostic = Diagnostic(node: Syntax(node), message: ModifiedCopyDiagnostic.notAStruct) 89 | context.diagnose(diagnostic) 90 | return [] 91 | } 92 | 93 | let structVisibility = structDeclSyntax.modifiers.visibilityText() ?? "internal" 94 | 95 | let variables = structDeclSyntax.memberBlock.members 96 | .compactMap { $0.decl.as(VariableDeclSyntax.self) } 97 | .filter { $0.bindings.allSatisfy { accessorIsAllowed($0.accessorBlock?.accessors) } } 98 | 99 | let bindings = variables.flatMap(\.bindings).filter { accessorIsAllowed($0.accessorBlock?.accessors) } 100 | 101 | let variablesCombi = variables.combinationsWithoutRepetition.filter { !$0.isEmpty } 102 | 103 | return variablesCombi.compactMap { variableCombi -> DeclSyntax? in 104 | let bindingsCombi = variableCombi.flatMap { $0.bindings } 105 | let many = bindingsCombi.count > 1 106 | 107 | let propertyNamesString = bindingsCombi.map { "`\($0.pattern)`" }.joined(separator: " and ") 108 | let parameterListString = bindingsCombi.map { binding in "\(binding.pattern): \(binding.typeAnnotation?.type.trimmed ?? "?")" }.joined(separator: ", ") 109 | 110 | return """ 111 | /// Returns a copy of the caller whose \(raw: many ? "values" : "value") for \(raw: propertyNamesString) \(raw: many ? "are" : "is") different. 112 | \(raw: structVisibility) func copy(\(raw: parameterListString)) -> Self { 113 | .init(\(raw: bindings.map { "\($0.pattern): \($0.pattern)" }.joined(separator: ", "))) 114 | } 115 | """ 116 | } 117 | } 118 | } 119 | 120 | private func accessorIsAllowed(_ accessor: AccessorBlockSyntax.Accessors?) -> Bool { 121 | guard let accessor else { return true } 122 | return switch accessor { 123 | case .accessors(let accessorDeclListSyntax): 124 | !accessorDeclListSyntax.contains { 125 | $0.accessorSpecifier.text == "get" || $0.accessorSpecifier.text == "set" 126 | } 127 | case .getter: 128 | false 129 | } 130 | } 131 | 132 | extension DeclModifierListSyntax { 133 | private static let visibilityModifiers: Set = ["private", "fileprivate", "internal", "package", "public", "open"] 134 | 135 | func visibilityText() -> String? { 136 | self.map(\.name.text) 137 | .first(where: { Self.visibilityModifiers.contains($0) }) 138 | } 139 | } 140 | 141 | extension Array { 142 | var combinationsWithoutRepetition: [[Element]] { 143 | guard !isEmpty else { return [[]] } 144 | return Array(self[1...]).combinationsWithoutRepetition.flatMap { [$0, [self[0]] + $0] } 145 | } 146 | } 147 | 148 | @main 149 | struct ModifiedCopyPlugin: CompilerPlugin { 150 | let providingMacros: [Macro.Type] = [ 151 | ModifiedCopyMacro.self, 152 | ModifiedCopyCombiMacro.self, 153 | ] 154 | } 155 | -------------------------------------------------------------------------------- /Tests/ModifiedCopyTests/ModifiedCopyTests.swift: -------------------------------------------------------------------------------- 1 | import SwiftSyntaxMacros 2 | import SwiftSyntaxMacrosTestSupport 3 | import XCTest 4 | import ModifiedCopyMacros 5 | import ModifiedCopy 6 | 7 | let testMacros: [String: Macro.Type] = [ 8 | "Copyable": ModifiedCopyMacro.self, 9 | "CopyableCombi": ModifiedCopyCombiMacro.self, 10 | ] 11 | 12 | @Copyable 13 | struct Person: Equatable { 14 | var name: String 15 | 16 | let age: Int 17 | 18 | /// This should not generate a copy function because it's not a stored property. 19 | var fullName: String { 20 | get { 21 | name 22 | } 23 | set { 24 | name = newValue 25 | } 26 | } 27 | 28 | /// This should not generate a copy function because it's not a stored property. 29 | var uppercasedName: String { 30 | name.uppercased() 31 | } 32 | 33 | var nickName: String? = "Bobby Tables" { 34 | didSet { 35 | print("nickName changed to \(nickName ?? "(nil)")") 36 | } 37 | } 38 | } 39 | 40 | final class ModifiedCopyTests: XCTestCase { 41 | func testMacroExpansion() { 42 | assertMacroExpansion( 43 | #""" 44 | @Copyable 45 | public struct Person { 46 | private(set) var name: String 47 | 48 | let age: Int 49 | 50 | private var favoriteColor: String 51 | 52 | /// This should not generate a copy function because it's not a stored property. 53 | var fullName: String { 54 | get { 55 | name 56 | } 57 | set { 58 | name = newValue 59 | } 60 | } 61 | 62 | /// This should not generate a copy function because it's not a stored property. 63 | var uppercasedName: String { 64 | name.uppercased() 65 | } 66 | 67 | var nickName: String? = "Bobby Tables" { 68 | didSet { 69 | print("nickName changed to \(nickName ?? "(nil)")") 70 | } 71 | } 72 | 73 | init(name: String, age: Int, favoriteColor: String, nickName: String? = nil) { 74 | self.name = name 75 | self.age = age 76 | self.favoriteColor = favoriteColor 77 | self.nickName = nickName 78 | } 79 | } 80 | """#, 81 | expandedSource: 82 | #""" 83 | public struct Person { 84 | private(set) var name: String 85 | 86 | let age: Int 87 | 88 | private var favoriteColor: String 89 | 90 | /// This should not generate a copy function because it's not a stored property. 91 | var fullName: String { 92 | get { 93 | name 94 | } 95 | set { 96 | name = newValue 97 | } 98 | } 99 | 100 | /// This should not generate a copy function because it's not a stored property. 101 | var uppercasedName: String { 102 | name.uppercased() 103 | } 104 | 105 | var nickName: String? = "Bobby Tables" { 106 | didSet { 107 | print("nickName changed to \(nickName ?? "(nil)")") 108 | } 109 | } 110 | 111 | init(name: String, age: Int, favoriteColor: String, nickName: String? = nil) { 112 | self.name = name 113 | self.age = age 114 | self.favoriteColor = favoriteColor 115 | self.nickName = nickName 116 | } 117 | 118 | /// Returns a copy of the caller whose value for `name` is different. 119 | private func copy(name: String) -> Self { 120 | .init(name: name, age: age, favoriteColor: favoriteColor, nickName: nickName) 121 | } 122 | 123 | /// Returns a copy of the caller whose value for `age` is different. 124 | public func copy(age: Int) -> Self { 125 | .init(name: name, age: age, favoriteColor: favoriteColor, nickName: nickName) 126 | } 127 | 128 | /// Returns a copy of the caller whose value for `favoriteColor` is different. 129 | private func copy(favoriteColor: String) -> Self { 130 | .init(name: name, age: age, favoriteColor: favoriteColor, nickName: nickName) 131 | } 132 | 133 | /// Returns a copy of the caller whose value for `nickName` is different. 134 | public func copy(nickName: String?) -> Self { 135 | .init(name: name, age: age, favoriteColor: favoriteColor, nickName: nickName) 136 | } 137 | } 138 | """#, 139 | macros: testMacros 140 | ) 141 | } 142 | 143 | func testCombiMacroExpansion() { 144 | assertMacroExpansion( 145 | #""" 146 | @CopyableCombi 147 | public struct Person { 148 | let name: String 149 | let age: Int 150 | } 151 | """#, 152 | expandedSource: 153 | #""" 154 | public struct Person { 155 | let name: String 156 | let age: Int 157 | 158 | /// Returns a copy of the caller whose value for `name` is different. 159 | public func copy(name: String) -> Self { 160 | .init(name: name, age: age) 161 | } 162 | 163 | /// Returns a copy of the caller whose value for `age` is different. 164 | public func copy(age: Int) -> Self { 165 | .init(name: name, age: age) 166 | } 167 | 168 | /// Returns a copy of the caller whose values for `name` and `age` are different. 169 | public func copy(name: String, age: Int) -> Self { 170 | .init(name: name, age: age) 171 | } 172 | } 173 | """#, 174 | macros: testMacros 175 | ) 176 | } 177 | 178 | func testNewLetValue() { 179 | let person = Person(name: "Walter White", age: 50, nickName: "Heisenberg") 180 | let copiedPerson = person.copy(age: 51) 181 | XCTAssertEqual(Person(name: "Walter White", age: 51, nickName: "Heisenberg"), copiedPerson) 182 | } 183 | 184 | func testNewVarValue() { 185 | let person = Person(name: "Walter White", age: 50, nickName: "Heisenberg") 186 | let copiedPerson = person.copy(name: "W.W.") 187 | XCTAssertEqual(Person(name: "W.W.", age: 50, nickName: "Heisenberg"), copiedPerson) 188 | } 189 | 190 | func testNewOptionalValue() { 191 | let person = Person(name: "Walter White", age: 50, nickName: "Heisenberg") 192 | let copiedPerson = person.copy(nickName: nil) 193 | XCTAssertEqual(Person(name: "Walter White", age: 50, nickName: nil), copiedPerson) 194 | } 195 | 196 | func testChainedNewValues() { 197 | let person = Person(name: "Walter White", age: 50, nickName: "Heisenberg") 198 | let copiedPerson = person.copy(name: "Skyler White").copy(age: 48) 199 | XCTAssertEqual(Person(name: "Skyler White", age: 48, nickName: "Heisenberg"), copiedPerson) 200 | } 201 | } 202 | --------------------------------------------------------------------------------