Generating Code And Other Mischief With Swift Package Manager Plugins - 360iDev, Denver, CO, August 2022

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GENERATING CODE AND OTHER MISCHIEF WITH SWIFT PACKAGE MANAGER PLUGINS 360IDEV | DENVER, CO | AUGUST 2022 ELLEN SHAPIRO | @DESIGNATEDNERD | GUSTO.COM

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ALCATRAZ

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! XCODE GHOST

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! XCODE GHOST

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! STRAWHORSE

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XCODE SOURCE EXTENSIONS

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REQUIRED HOST MAC APP

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REQUIRED HOST MAC APP ▸ ! Can now be distributed easily on the Mac App store

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REQUIRED HOST MAC APP ▸ ! Can now be distributed easily on the Mac App store ▸ " Sandboxing restrictions

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REQUIRED HOST MAC APP ▸ ! Can now be distributed easily on the Mac App store ▸ " Sandboxing restrictions ▸ # Often winds up with an empty app

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func perform(with invocation: XCSourceEditorCommandInvocation, completionHandler: @escaping (Error?) -> Void) { // Actual code of plugin }

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ONLY SINGLE-FILE TEXT BUFFER ACCESS

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ONLY SINGLE-FILE TEXT BUFFER ACCESS ▸ ! Does allow at least some sorting, linting, formatting

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ONLY SINGLE-FILE TEXT BUFFER ACCESS ▸ ! Does allow at least some sorting, linting, formatting ▸ ☹ Only ever the current file

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ONLY SINGLE-FILE TEXT BUFFER ACCESS ▸ ! Does allow at least some sorting, linting, formatting ▸ ☹ Only ever the current file ▸ # No access to the AST

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ONLY SINGLE-FILE TEXT BUFFER ACCESS ▸ ! Does allow at least some sorting, linting, formatting ▸ ☹ Only ever the current file ▸ # No access to the AST ▸ $ No access to file or project structure

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FURTHER INVOCATION LIMITATIONS

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FURTHER INVOCATION LIMITATIONS ▸ ! Cannot run in background

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FURTHER INVOCATION LIMITATIONS ▸ ! Cannot run in background ▸ " Must be actively invoked by the user

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FURTHER INVOCATION LIMITATIONS ▸ ! Cannot run in background ▸ " Must be actively invoked by the user ▸ # No default key binding

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SWIFT PACKAGE MANAGER ! PLUGINS

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✅ SWIFT 5.6

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✅ SWIFT 5.6 ! XCODE 14

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1. COMMAND PLUGINS 2. BUILD TOOL PLUGINS

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COMMAND PLUGINS

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CODE FROM "CREATE SWIFT PACKAGE PLUGINS" HTTPS://DEVELOPER.APPLE.COM/VIDEOS/PLAY/WWDC2022/110401/

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COMMAND PLUGINS ▸ Can ask permission to write in the package directory

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// Package.swift .plugin( name: "GenerateContributors", capability: .command( intent: .custom(verb: "regenerate-contributors-list", description: "Generates the CONTRIBUTORS.txt file based on Git logs"), permissions: [ .writeToPackageDirectory(reason: "This command write the new CONTRIBUTORS.txt to the source root.") ] )),

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COMMAND PLUGINS ▸ Can ask permission to write in the package directory ▸ Can be invoked at the command line

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// Get all plugins available on a particular package swift package plugin --list // Run a specific plugin, in this case GenerateContributors swift package regenerate-contributors-list

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COMMAND PLUGINS ▸ Can ask permission to write in the package directory ▸ Can be invoked at the command line ▸ Can be invoked from a menu item in Xcode

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COMMAND PLUGINS ▸ Can ask permission to write in the package directory ▸ Can be invoked at the command line ▸ Can be invoked from a menu item Xcode ▸ Either way, must be invoked separately from the build process

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BUILD TOOL PLUGINS

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BUILD TOOL PLUGINS RUN AUTOMATICALLY ON EVERY BUILD

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BUILD TOOL PLUGINS (THE THING I REALLY WANT TO USE)

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THE MORE COMPLICATED BUT LESS COMPLICATED WAY: EMBED A PACKAGE IN YOUR .XCODEPROJ

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MORE COMPLICATED (YOU HAVE TO ADD A WHOLE SWIFT PACKAGE TO YOUR PROJECT)

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LESS COMPLICATED (IT WORKS WAY MORE RELIABLY)

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SAMPLE APP https://github.com/designatednerd/ RadioactiveCat

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via https://energyeducation.ca/encyclopedia/Half_life

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BUILD TOOL EASY MODE BRING IN SOMEONE ELSE'S PLUGIN

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DO NIL DISTURB HTTPS://GITHUB.COM/ICANZILB/ DONILDISTURBPLUGIN

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// Package.swift .dependencies: [ .package(url: "https://github.com/icanzilb/ DoNilDisturbPlugin.git", from: "0.0.5"), ]

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// Package.swift .target( name: "Cats", dependencies: [ ], plugins: [ .plugin(name: "DoNilDisturbPlugin", package: "DoNilDisturbPlugin") ] ),

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DO NOT BLINDLY CLICK TRUST & ENABLE ALL

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BUILD TOOL HARD MODE: CREATE YOUR OWN PLUGIN

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DON'T BUILD YOUR PLUGIN AND THE PACKAGE YOU'RE TESTING IT AGAINST IN THE SAME REPO

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GITHUB.COM/DESIGNATEDNERD/ DATEDIMAGEGENERATOR

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PLUGIN VS. EXECUTABLE

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// File structure of the Swift Lib ! DatedImageGenerator ! Plugins ! DatedImageGenerator " DatedImageGenerator.swift ! Sources ! DatedImage " DatedImage.swift " ExifDateFormatter.swift ! DatedImageGeneratorExecutable " DatedImageGeneratorExecutable.swift ! Tests ! DatedImageGeneratorTests " DatedImageGeneratorExecutable.swift " Media.xcassets

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// File structure of the Swift Lib ! DatedImageGenerator ! Plugins ! DatedImageGenerator " DatedImageGenerator.swift ! Sources ! DatedImage // <-- Exported library used in executable and main app " DatedImage.swift " ExifDateFormatter.swift ! DatedImageGeneratorExecutable " DatedImageGeneratorExecutable.swift ! Tests ! DatedImageGeneratorTests " DatedImageGeneratorExecutable.swift " Media.xcassets

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// File structure of the Swift Lib ! DatedImageGenerator ! Plugins ! DatedImageGenerator " DatedImageGenerator.swift ! Sources ! DatedImage // <-- Exported Framework used in executable and main app " DatedImage.swift " ExifDateFormatter.swift ! DatedImageGeneratorExecutable // <-- The thing that does all the work " DatedImageGeneratorExecutable.swift ! Tests ! DatedImageGeneratorTests " DatedImageGeneratorExecutable.swift " Media.xcassets

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// Plugins/DatedImageGenerator.swift @main struct DatedImageGenerator: BuildToolPlugin { func createBuildCommands(context: PluginContext, target: Target) async throws -> [Command] { // TODO: Create info for build command return [ .buildCommand( displayName: "Generate Dated Images", executable: try context.tool(named: "DatedImageGeneratorExecutable").path, // more to come here arguments: "TODO", outputFiles: ["TODO"] ) ] } }

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WHAT'S IN THE EXECUTABLE?

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// Sources/DatedImageGeneratorExecutable/ // DatedImageGeneratorExecutable.swift @main struct DatedImageGeneratorExecutable { static func main() throws { // How do we get information from the Plugin? } }

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// Sources/DatedImageGeneratorExecutable/ // DatedImageGeneratorExecutable.swift @main struct DatedImageGeneratorExecutable { static func main() throws { // Grab the 2nd argument as a string ProcessInfo.processInfo.arguments[1] } }

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// Sources/DatedImageGeneratorExecutable/ // DatedImageGeneratorExecutable.swift @main struct DatedImageGeneratorExecutable { static func main() throws { // Turn it into Data Data(ProcessInfo.processInfo.arguments[1].utf8)) } }

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// Sources/DatedImageGeneratorExecutable/ // DatedImageGeneratorExecutable.swift @main struct DatedImageGeneratorExecutable { static func main() throws { // Decode it into a codable object! let invocation = try JSONDecoder() .decode(PluginInvocation.self, from: Data(ProcessInfo.processInfo.arguments[1].utf8)) } }

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"I should just put the codable object in the executable and import it into the plugin"

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// One copy of this in the plugin, one in the executable struct PluginInvocation: Codable { let catalogPaths: [String] let outputPath: String func encodedString() throws -> String { let data = try JSONEncoder().encode(self) return String(decoding: data, as: UTF8.self) } }

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// One copy of this in the plugin, one in the executable // (or share with a common lib) struct PluginInvocation: Codable { let catalogPaths: [String] let outputPath: String func encodedString() throws -> String { let data = try JSONEncoder().encode(self) return String(decoding: data, as: UTF8.self) } }

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// Plugins/DatedImageGenerator.swift @main struct DatedImageGenerator: BuildToolPlugin { func createBuildCommands(context: PluginContext, target: Target) async throws -> [Command] { guard let target = target as? SourceModuleTarget else { throw ImageGenError.notASourceModule } let assetCatalogPaths = target.sourceFiles(withSuffix: "xcassets") .compactMap { assetCatalog in return assetCatalog.path.string } let outputPath = context.pluginWorkDirectory .appending(["DatedImages.swift"]) let invocation = PluginInvocation(catalogPaths: assetCatalogPaths, outputPath: outputPath.string) return [ .buildCommand( displayName: "Generate Dated Images", executable: try context.tool(named: "DatedImageGeneratorExecutable").path, arguments: [try invocation.encodedString()], outputFiles: [outputPath] ) ] } }

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// Plugins/DatedImageGenerator.swift @main struct DatedImageGenerator: BuildToolPlugin { func createBuildCommands(context: PluginContext, target: Target) async throws -> [Command] { guard let target = target as? SourceModuleTarget else { throw ImageGenError.notASourceModule } let assetCatalogPaths = target.sourceFiles(withSuffix: "xcassets") .compactMap { assetCatalog in return assetCatalog.path.string } let outputPath = context.pluginWorkDirectory .appending(["DatedImages.swift"]) let invocation = PluginInvocation(catalogPaths: assetCatalogPaths, outputPath: outputPath.string) return [ .buildCommand( displayName: "Generate Dated Images", executable: try context.tool(named: "DatedImageGeneratorExecutable").path, arguments: [try invocation.encodedString()], outputFiles: [outputPath] ) ] } }

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! TARGET (TECHNICALLY PACKAGEPLUGIN.TARGET)

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// Plugins/DatedImageGenerator.swift @main struct DatedImageGenerator: BuildToolPlugin { func createBuildCommands(context: PluginContext, target: Target) async throws -> [Command] { guard let target = target as? SourceModuleTarget else { throw ImageGenError.notASourceModule } let assetCatalogPaths = target.sourceFiles(withSuffix: "xcassets") .compactMap { assetCatalog in return assetCatalog.path.string } let outputPath = context.pluginWorkDirectory .appending(["DatedImages.swift"]) let invocation = PluginInvocation(catalogPaths: assetCatalogPaths, outputPath: outputPath.string) return [ .buildCommand( displayName: "Generate Dated Images", executable: try context.tool(named: "DatedImageGeneratorExecutable").path, arguments: [try invocation.encodedString()], outputFiles: [outputPath] ) ] } }

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! PLUGIN CONTEXT (TECHNICALLY PACKAGEPLUGIN.PLUGINCONTEXT)

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PLUGINWORKDIRECTORY IS YOUR SANDBOX

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// Plugins/DatedImageGenerator.swift @main struct DatedImageGenerator: BuildToolPlugin { func createBuildCommands(context: PluginContext, target: Target) async throws -> [Command] { guard let target = target as? SourceModuleTarget else { throw ImageGenError.notASourceModule } let assetCatalogPaths = target.sourceFiles(withSuffix: "xcassets") .compactMap { assetCatalog in return assetCatalog.path.string } let outputPath = context.pluginWorkDirectory .appending(["DatedImages.swift"]) let invocation = PluginInvocation(catalogPaths: assetCatalogPaths, outputPath: outputPath.string) return [ .buildCommand( displayName: "Generate Dated Images", executable: try context.tool(named: "DatedImageGeneratorExecutable").path, arguments: [try invocation.encodedString()], outputFiles: [outputPath] ) ] } }

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// Plugins/DatedImageGenerator.swift @main struct DatedImageGenerator: BuildToolPlugin { func createBuildCommands(context: PluginContext, target: Target) async throws -> [Command] { guard let target = target as? SourceModuleTarget else { throw ImageGenError.notASourceModule } let assetCatalogPaths = target.sourceFiles(withSuffix: "xcassets") .compactMap { assetCatalog in return assetCatalog.path.string } let outputPath = context.pluginWorkDirectory .appending(["DatedImages.swift"]) let invocation = PluginInvocation(catalogPaths: assetCatalogPaths, outputPath: outputPath.string) return [ .buildCommand( displayName: "Generate Dated Images", executable: try context.tool(named: "DatedImageGeneratorExecutable").path, arguments: [try invocation.encodedString()], outputFiles: [outputPath] ) ] } }

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QUICK RECAP OF PLUGIN CREATION

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QUICK RECAP OF PLUGIN CREATION ▸ Create a plugin in Plugins

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QUICK RECAP OF PLUGIN CREATION ▸ Create a plugin in Plugins ▸ Create an executable it will call in Sources

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QUICK RECAP OF PLUGIN CREATION ▸ Create a plugin in Plugins ▸ Create an executable it will call in Sources ▸ Use a codable object to pass data between them

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QUICK RECAP OF PLUGIN CREATION ▸ Create a plugin in Plugins ▸ Create an executable it will call in Sources ▸ Use a codable object to pass data between them ▸ Note that the plugin depends on but cannot import the executable

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! BACK TO THE KITTAHS!

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// In Cats/Package.swift dependencies: [ .package(url: "https://github.com/designatednerd/ DatedImageGenerator.git", from: "0.0.1"), .package(url: "https://github.com/icanzilb/ DoNilDisturbPlugin.git", from: "0.0.5"), ],

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// In Cats/Package.swift .target( name: "Cats", dependencies: [ .product(name: "DatedImage", package: "DatedImageGenerator"), ], plugins: [ .plugin(name: "DatedImageGenerator", package: "DatedImageGenerator"), .plugin(name: "DoNilDisturbPlugin", package: "DoNilDisturbPlugin") ] ),

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WHAT ABOUT RUNNING PLUGINS ON AN APP TARGET?

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XCODE PROJECT PLUGIN

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XCODE PROJECT PLUGIN (A KIND OF BUILD TOOL PLUGIN)

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#if canImport(XcodeProjectPlugin) import XcodeProjectPlugin extension DatedImageGenerator: XcodeBuildToolPlugin { func createBuildCommands(context: XcodePluginContext, target: XcodeTarget) throws -> [Command] { let assetCatalogPaths = context.xcodeProject.filePaths .filter({ $0.string.hasSuffix("xcassets")}) .map { $0.string } // Rest of the code the same as in the main plugin } } #endif

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SPM PLUGIN LIMITATIONS

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SPM PLUGIN LIMITATIONS (that I've found so far)

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SPM PLUGIN LIMITATIONS (that I've found so far) ▸ Still no UI for you

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SPM PLUGIN LIMITATIONS (that I've found so far) ▸ Still no UI for you ▸ You can't even ask to use the network

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SPM PLUGIN LIMITATIONS (that I've found so far) ▸ Still no UI for you ▸ You can't even ask to use the network ▸ You can't share data between plugins

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SPM PLUGIN LIMITATIONS (that I've found so far) ▸ Still no UI for you ▸ You can't even ask to use the network ▸ You can't share data between plugins ▸ Can't do anything with build results

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! PLUGIN WISH LIST

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PLUGIN WISH LIST ▸ File metadata

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PLUGIN WISH LIST ▸ File metadata ▸ Ability to show UI in Xcode

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OBLIGATORY SUMMARY SLIDE

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OBLIGATORY SUMMARY SLIDE ▸ Alcatraz

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OBLIGATORY SUMMARY SLIDE ▸ Alcatraz ! " Xcode 8 Extensions

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OBLIGATORY SUMMARY SLIDE ▸ Alcatraz ! " Xcode 8 Extensions ▸ SPM Plugins to the rescue!

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OBLIGATORY SUMMARY SLIDE ▸ Alcatraz ! " Xcode 8 Extensions ▸ SPM Plugins to the rescue! ▸ Command plugins: On demand, Build tool plugins: On every build

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OBLIGATORY SUMMARY SLIDE ▸ Alcatraz ! " Xcode 8 Extensions ▸ SPM Plugins to the rescue! ▸ Command plugins: On demand, Build tool plugins: On every build ▸ Security: Be super-mindful of which plugins you use

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THANK YOU!

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SWIFT-EVOLUTION LINKS! ▸ SE-0303: Extensible Build Tools github.com/apple/swift-evolution/ blob/main/proposals/0303-swiftpm-extensible-build-tools.md ▸ SE-0325: Additional Plugin APIs github.com/apple/swift-evolution/ blob/main/proposals/0325-swiftpm-additional-plugin-apis.md ▸ SE-0332: SPM Command Plugins github.com/apple/swift-evolution/ blob/main/proposals/0332-swiftpm-command-plugins.md

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! SLIGHTLY TERRIFYING LINKS! ▸ Xcode Ghost details: en.wikipedia.org/wiki/XcodeGhost ▸ Strawhorse leaked document: theintercept.com/document/ 2015/03/10/strawhorse-attacking-macos-ios-software- development-kit ▸ Strawhorse Context: theintercept.com/2015/03/10/ispy-cia- campaign-steal-apples-secrets/

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! PLUGIN LINKS! ▸ Do Nil Disturb: github.com/icanzilb/DoNilDisturbPlugin ▸ Swift SafeURL: github.com/baguio/SwiftSafeURL