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SwiftGen-Build-Tool-Package-Plugins.md

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Creating a SwiftGen Build Tool Package Plugin

SE-0325 introduced the ability to create Swift Package Plugins for our Swift Packages, and it was officially released in Swift 5.6.

Using this new functionality it is possible to create a SwiftGen plugin for our Swift Packages which automatically keeps our generated files up to date.

SwiftGen provides an official plugin that provides most of the functionality you may ever need. The rest of this article is for if you ever want to create your own SwiftGen plugin.

Making the SwiftGen binary available to your plugin

Simply add the following binary target to your Package.swift. Each recent SwiftGen release includes a .artifactbundle compatible with Swift Plugin development.

targets: [
    .plugin(
        name: "YourSwiftGenPlugin",
        capability: .buildTool(),
        dependencies: [
            "swiftgen"
        ]
    ),    
    .binaryTarget(
        name: "swiftgen",
        url: "https://github.com/SwiftGen/SwiftGen/releases/download/6.5.1/swiftgen.artifactbundle.zip",
        checksum: "a8e445b41ac0fd81459e07657ee19445ff6cbeef64eb0b3df51637b85f925da8"
    )
]

👋 Remember to replace the version and checksum with appropriate values, you can find the most recent SwiftGen releases HERE

🧮 To generate the checksum yourself you can use swift package compute-checksum swiftgen.artifactbundle.zip.

Using the tool in your plugin

After the SwiftGen binary has been introduced to your package, your plugin will be able to execute SwiftGen by searching the context for a tool named swiftgen.

A barebones example:

import PackagePlugin
import Foundation

@main
struct SwiftGenPlugin: BuildToolPlugin {
    func createBuildCommands(context: PluginContext, target: Target) throws -> [Command] {
        [
            Command.prebuildCommand(
                displayName: "Running SwiftGen",
                executable: try context.tool(named: "swiftgen").path,
                arguments: [
                    "config",
                    "run",
                    "--config", "\(target.directory.appending("swiftgen.yml"))"
                ],
                environment: [
                    "PROJECT_DIR": "\(context.package.directory)",
                    "TARGET_NAME": "\(target.name)",
                    "DERIVED_SOURCES_DIR": "\(context.pluginWorkDirectory)",
                ],
                outputFilesDirectory: context.pluginWorkDirectory
            )
        ]
    }
}

Examples

Other examples of Swift package build tool plugins development