Newbie’s information to Swift package deal supervisor command plugins

Introduction to Swift Package deal Supervisor plugins

To begin with I would like to speak a number of phrases in regards to the new SPM plugin infrastructure, that was launched within the Swift 5.6 launch. The very first proposal describes the detailed design of the plugin API with some plugin examples, that are fairly helpful. Actually talking I used to be a bit to lazy to fastidiously learn by the whole documentation, it is fairly lengthy, however lengthy story quick, you possibly can create the next plugin sorts with the presently current APIs:

• Construct instruments – might be invoked by way of the SPM targets

• pre-build – runs earlier than the construct begins
• construct – runs throughout the construct

• Instructions – might be invoked by way of the command line

• supply code formatting – modifies the code inside package deal
• documentation technology – generate docs for the package deal
• customized – consumer outlined intentions

For the sake of simplicity on this tutorial I am solely going to put in writing a bit in regards to the second class, aka. the command plugins. These plugins have been a bit extra fascinating for me, as a result of I wished to combine my deployment workflow into SPM, so I began to experiment with the plugin API to see how onerous it’s to construct such a factor. Seems it is fairly simple, however the developer expertise it isn’t that good. 😅

Constructing a supply code formatting plugin

The very very first thing I wished to combine with SPM was SwiftLint, since I used to be not capable of finding a plugin implementation that I might use I began from scratch. As a place to begin I used to be utilizing the instance code from the Package deal Supervisor Command Plugins proposal.

mkdir Instance
cd Instance
swift package deal init --type=library

I began with a model new package deal, utilizing the swift package deal init command, then I modified the Package deal.swift file in line with the documentation. I’ve additionally added SwiftLint as a package deal dependency so SPM can obtain & construct the and hopefully my customized plugin command can invoke the swiftlint executable when it’s wanted.

import PackageDescription

let package deal = Package deal(
    identify: "Instance",
    platforms: [
        .macOS(.v10_15),
    ],
    merchandise: [
        .library(name: "Example", targets: ["Example"]),
        .plugin(identify: "MyCommandPlugin", targets: ["MyCommandPlugin"]),
    ],
    dependencies: [
        .package(url: "https://github.com/realm/SwiftLint", branch: "master"),
    ],
    targets: [
        .target(name: "Example", dependencies: []),
        .testTarget(identify: "ExampleTests", dependencies: ["Example"]),
       
        .plugin(identify: "MyCommandPlugin",
                functionality: .command(
                    intent: .sourceCodeFormatting(),
                    permissions: [
                        .writeToPackageDirectory(reason: "This command reformats source files")
                    ]
                ),
                dependencies: [
                    .product(name: "swiftlint", package: "SwiftLint"),
                ]),
    ]
)

I’ve created a Plugins listing with a major.swift file proper subsequent to the Sources folder, with the next contents.

import PackagePlugin
import Basis

@major
struct MyCommandPlugin: CommandPlugin {
    
    func performCommand(context: PluginContext, arguments: [String]) throws {
        let device = attempt context.device(named: "swiftlint")
        let toolUrl = URL(fileURLWithPath: device.path.string)
        
        for goal in context.package deal.targets {
            guard let goal = goal as? SourceModuleTarget else { proceed }

            let course of = Course of()
            course of.executableURL = toolUrl
            course of.arguments = [
                "(target.directory)",
                "--fix",
               
            ]

            attempt course of.run()
            course of.waitUntilExit()
            
            if course of.terminationReason == .exit && course of.terminationStatus == 0 {
                print("Formatted the supply code in (goal.listing).")
            }
            else {
                let drawback = "(course of.terminationReason):(course of.terminationStatus)"
                Diagnostics.error("swift-format invocation failed: (drawback)")
            }
        }
    }
}

The snippet above ought to find the swiftlint device utilizing the plugins context then it will iterate by the accessible package deal targets, filter out non source-module targets and format solely these targets that comprises precise Swift supply recordsdata. The method object ought to merely invoke the underlying device, we will wait till the kid (swiftlint invocation) course of exists and hopefully we’re good to go. 🤞

Replace: kalKarmaDev advised me that it’s attainable to move the --in-process-sourcekit argument to SwiftLint, it will repair the underlying problem and the supply recordsdata are literally mounted.

I wished to listing the accessible plugins & run my supply code linter / formatter utilizing the next shell instructions, however sadly looks as if the swiftlint invocation half failed for some unusual cause.

swift package deal plugin --list
    swift package deal format-source-code #will not work, wants entry to supply recordsdata
    swift package deal --allow-writing-to-package-directory format-source-code

Looks as if there’s an issue with the exit code of the invoked swiftlint course of, so I eliminated the success examine from the plugin supply to see if that is inflicting the difficulty or not additionally tried to print out the executable command to debug the underlying drawback.

import PackagePlugin
import Basis

@major
struct MyCommandPlugin: CommandPlugin {
    
    func performCommand(context: PluginContext, arguments: [String]) throws {
        let device = attempt context.device(named: "swiftlint")
        let toolUrl = URL(fileURLWithPath: device.path.string)
        
        for goal in context.package deal.targets {
            guard let goal = goal as? SourceModuleTarget else { proceed }

            let course of = Course of()
            course of.executableURL = toolUrl
            course of.arguments = [
                "(target.directory)",
                "--fix",
            ]

            print(toolUrl.path, course of.arguments!.joined(separator: " "))

            attempt course of.run()
            course of.waitUntilExit()
        }
    }
}

Deliberately made a small “mistake” within the Instance.swift supply file, so I can see if the swiftlint –fix command will remedy this problem or not. 🤔

public struct Instance {
    public personal(set) var textual content = "Hi there, World!"

    public init() {
        let xxx :Int = 123
    }
}

Seems, once I run the plugin by way of the Course of invocation, nothing occurs, however once I enter the next code manually into the shell, it simply works.

/Customers/tib/Instance/.construct/arm64-apple-macosx/debug/swiftlint /Customers/tib/Instance/Exams/Instance --fix
/Customers/tib/Instance/.construct/arm64-apple-macosx/debug/swiftlint /Customers/tib/Instance/Exams/ExampleTests --fix

All proper, so we undoubtedly have an issue right here… I attempted to get the usual output message and error message from the working course of, looks as if swiftlint runs, however one thing within the SPM infrastructure blocks the code modifications within the package deal. After a number of hours of debugging I made a decision to offer a shot to swift-format, as a result of that is what the official docs counsel. 🤷‍♂️

import PackageDescription

let package deal = Package deal(
    identify: "Instance",
    platforms: [
        .macOS(.v10_15),
    ],
    merchandise: [
        .library(name: "Example", targets: ["Example"]),
        .plugin(identify: "MyCommandPlugin", targets: ["MyCommandPlugin"]),
    ],
    dependencies: [
        .package(url: "https://github.com/apple/swift-format", exact: "0.50600.1"),
    ],
    targets: [
        .target(name: "Example", dependencies: []),
        .testTarget(identify: "ExampleTests", dependencies: ["Example"]),
       
        .plugin(identify: "MyCommandPlugin",
                functionality: .command(
                    intent: .sourceCodeFormatting(),
                    permissions: [
                        .writeToPackageDirectory(reason: "This command reformats source files")
                    ]
                ),
                dependencies: [
                    .product(name: "swift-format", package: "swift-format"),
                ]),
    ]
)

Modified each the Package deal.swift file and the plugin supply code, to make it work with swift-format.

import PackagePlugin
import Basis

@major
struct MyCommandPlugin: CommandPlugin {
    
    func performCommand(context: PluginContext, arguments: [String]) throws {
        let swiftFormatTool = attempt context.device(named: "swift-format")
        let swiftFormatExec = URL(fileURLWithPath: swiftFormatTool.path.string)

        
        for goal in context.package deal.targets {
            guard let goal = goal as? SourceModuleTarget else { proceed }

            let course of = Course of()
            course of.executableURL = swiftFormatExec
            course of.arguments = [

                "--in-place",
                "--recursive",
                "(target.directory)",
            ]
            attempt course of.run()
            course of.waitUntilExit()

            if course of.terminationReason == .exit && course of.terminationStatus == 0 {
                print("Formatted the supply code in (goal.listing).")
            }
            else {
                let drawback = "(course of.terminationReason):(course of.terminationStatus)"
                Diagnostics.error("swift-format invocation failed: (drawback)")
            }
        }
    }
}

I attempted to run once more the very same package deal plugin command to format my supply recordsdata, however this time swift-format was doing the code formatting as a substitute of swiftlint.

swift package deal --allow-writing-to-package-directory format-source-code
// ... loading dependencies
Construct full! (6.38s)
Formatted the supply code in /Customers/tib/Linter/Exams/ExampleTests.
Formatted the supply code in /Customers/tib/Linter/Sources/Instance.

Labored like a allure, my Instance.swift file was mounted and the : was on the left facet… 🎊

public struct Instance {
    public personal(set) var textual content = "Hi there, World!"

    public init() {
        let xxx: Int = 123
    }
}

Yeah, I’ve made some progress, however it took me numerous time to debug this problem and I do not like the truth that I’ve to fiddle with processes to invoke different instruments… my intestine tells me that SwiftLint is just not following the usual shell exit standing codes and that is inflicting some points, perhaps it is spawning baby processes and that is the issue, I actually do not know however I do not wished to waste extra time on this problem, however I wished to maneuver ahead with the opposite class. 😅

Integrating the DocC plugin with SPM

As a primary step I added some dummy feedback to my Instance library to have the ability to see one thing within the generated documentation, nothing fancy just a few one-liners. 📖

public struct Instance {

    
    public personal(set) var textual content = "Hi there, World!"
    
    
    public init() {
        let xxx: Int = 123
    }
}

I found that Apple has an official DocC plugin, so I added it as a dependency to my undertaking.

import PackageDescription

let package deal = Package deal(
    identify: "Instance",
    platforms: [
        .macOS(.v10_15),
    ],
    merchandise: [
        .library(name: "Example", targets: ["Example"]),
        .plugin(identify: "MyCommandPlugin", targets: ["MyCommandPlugin"]),
    ],
    dependencies: [
        .package(url: "https://github.com/apple/swift-format", exact: "0.50600.1"),
        .package(url: "https://github.com/apple/swift-docc-plugin", from: "1.0.0"),

    ],
    targets: [
        .target(name: "Example", dependencies: []),
        .testTarget(identify: "ExampleTests", dependencies: ["Example"]),
       
        .plugin(identify: "MyCommandPlugin",
                functionality: .command(
                    intent: .sourceCodeFormatting(),
                    permissions: [
                        .writeToPackageDirectory(reason: "This command reformats source files")
                    ]
                ),
                dependencies: [
                    .product(name: "swift-format", package: "swift-format"),
                ]),
    ]
)

Two new plugin instructions have been accessible after I executed the plugin listing command.

swift package deal plugin --list

Tried to run the primary one, and luckily the doccarchive file was generated. 😊

swift package deal generate-documentation

Additionally tried to preview the documentation, there was a notice in regards to the --disable-sandbox flag within the output, so I merely added it to my authentic command and…

swift package deal preview-documentation 

swift package deal --disable-sandbox preview-documentation

Magic. It labored and my documentation was accessible. Now that is how plugins ought to work, I beloved this expertise and I actually hope that increasingly official plugins are coming quickly. 😍

Constructing a customized intent command plugin

I wished to construct a small executable goal with some bundled sources and see if a plugin can deploy the executable binary with the sources. This may very well be very helpful once I deploy feather apps, I’ve a number of module bundles there and now I’ve to manually copy all the things… 🙈

import PackageDescription

let package deal = Package deal(
    identify: "Instance",
    platforms: [
        .macOS(.v10_15),
    ],
    merchandise: [
        .library(name: "Example", targets: ["Example"]),
        .executable(identify: "MyExample", targets: ["MyExample"]),
        .plugin(identify: "MyCommandPlugin", targets: ["MyCommandPlugin"]),
        .plugin(identify: "MyDistCommandPlugin", targets: ["MyDistCommandPlugin"]),
    ],
    dependencies: [
        .package(url: "https://github.com/apple/swift-format", exact: "0.50600.1"),
        .package(url: "https://github.com/apple/swift-docc-plugin", from: "1.0.0"),

    ],
    targets: [
        .executableTarget(name: "MyExample",
                          resources: [
                            .copy("Resources"),
                          ], plugins: [
                            
                          ]),
        .goal(identify: "Instance", dependencies: []),
        .testTarget(identify: "ExampleTests", dependencies: ["Example"]),
       
        .plugin(identify: "MyCommandPlugin",
                functionality: .command(
                    intent: .sourceCodeFormatting(),
                    permissions: [
                        .writeToPackageDirectory(reason: "This command reformats source files")
                    ]
                ),
                dependencies: [
                    .product(name: "swift-format", package: "swift-format"),
                ]),
        
        .plugin(identify: "MyDistCommandPlugin",
                functionality: .command(
                    intent: .customized(verb: "dist", description: "Create dist archive"),
                    permissions: [
                        .writeToPackageDirectory(reason: "This command deploys the executable")
                    ]
                ),
                dependencies: [
                ]),
    ]
)

As a primary step I created a brand new executable goal known as MyExample and a brand new MyDistCommandPlugin with a customized verb. Contained in the Sources/MyExample/Sources folder I’ve positioned a easy check.json file with the next contents.

{
    "success": true
}

The major.swift file of the MyExample goal seems to be like this. It simply validates that the useful resource file is out there and it merely decodes the contents of it and prints all the things to the usual output. 👍

import Basis

guard let jsonFile = Bundle.module.url(forResource: "Sources/check", withExtension: "json") else {
    fatalError("Bundle file not discovered")
}
let jsonData = attempt Information(contentsOf: jsonFile)

struct Json: Codable {
    let success: Bool
}

let json = attempt JSONDecoder().decode(Json.self, from: jsonData)

print("Is success?", json.success)

Contained in the Plugins folder I’ve created a major.swift file beneath the MyDistCommandPlugin folder.

import PackagePlugin
import Basis

@major
struct MyDistCommandPlugin: CommandPlugin {
    
    func performCommand(context: PluginContext, arguments: [String]) throws {
        
        
    }
}

Now I used to be capable of re-run the swift package deal plugin --list command and the dist verb appeared within the listing of obtainable instructions. Now the one query is: how will we get the artifacts out of the construct listing? Fortuitously the third instance of the instructions proposal is kind of related.

import PackagePlugin
import Basis

@major
struct MyDistCommandPlugin: CommandPlugin {
    
    func performCommand(context: PluginContext, arguments: [String]) throws {
        let cpTool = attempt context.device(named: "cp")
        let cpToolURL = URL(fileURLWithPath: cpTool.path.string)

        let consequence = attempt packageManager.construct(.product("MyExample"), parameters: .init(configuration: .launch, logging: .concise))
        guard consequence.succeeded else {
            fatalError("could not construct product")
        }
        guard let executable = consequence.builtArtifacts.first(the place : { $0.variety == .executable }) else {
            fatalError("could not discover executable")
        }
        
        let course of = attempt Course of.run(cpToolURL, arguments: [
            executable.path.string,
            context.package.directory.string,
        ])
        course of.waitUntilExit()

        let exeUrl = URL(fileURLWithPath: executable.path.string).deletingLastPathComponent()
        let bundles = attempt FileManager.default.contentsOfDirectory(atPath: exeUrl.path).filter { $0.hasSuffix(".bundle") }

        for bundle in bundles {
            let course of = attempt Course of.run(cpToolURL, arguments: ["-R",
                                                                    exeUrl.appendingPathComponent(bundle).path,
                                                                    context.package.directory.string,
                                                                ])
            course of.waitUntilExit()
        }
    }
}

So the one drawback was that I used to be not capable of get again the bundled sources, so I had to make use of the URL of the executable file, drop the final path part and browse the contents of that listing utilizing the FileManager to get again the .bundle packages within that folder.

Sadly the builtArtifacts property solely returns the executables and libraries. I actually hope that we’ll get assist for bundles as properly sooner or later so this hacky resolution might be prevented for good. Anyway it really works simply nice, however nonetheless it is a hack, so use it fastidiously. ⚠️

swift package deal --allow-writing-to-package-directory dist
./MyExample 

I used to be capable of run my customized dist command with out additional points, in fact you need to use further arguments to customise your plugin or add extra flexibility, the examples within the proposal are just about okay, however it’s fairly unlucky that there is no such thing as a official documentation for Swift package deal supervisor plugins simply but. 😕

Conclusion

Studying about command plugins was enjoyable, however to start with it was annoying as a result of I anticipated a bit higher developer expertise relating to the device invocation APIs. In abstract I can say that that is only the start. It is similar to the async / await and actors addition to the Swift language. The function itself is there, it is largely able to go, however not many builders are utilizing it every day. These items would require time and hopefully we’ll see much more plugins afterward… 💪