Automatically open a browser window when Dev Server starts (#117)

* Automatically open dev server in system browser

* Allow opting out of automatically opening in browser

* Update readme with new behavior

README.md

@@ -49,8 +49,7 @@ new [Tokamak](https://tokamak.dev/) project, while `carton init --template basic
 currently).
 
 The `carton dev` command builds your project with the SwiftWasm toolchain and starts an HTTP server
-that hosts your WebAssembly executable and a corresponding JavaScript entrypoint that loads it. Open
-[http://127.0.0.1:8080/](http://127.0.0.1:8080/) in your browser to see the app running. You can
+that hosts your WebAssembly executable and a corresponding JavaScript entrypoint that loads it. The app, reachable at [http://127.0.0.1:8080/](http://127.0.0.1:8080/), will automatically open in your default web browser. You can
 edit the app source code in your favorite editor and save it, `carton` will immediately rebuild the
 app and reload all browser tabs that have the app open. You can also pass a `--verbose` flag to
 keep the build process output available, otherwise stale output is cleaned up from your terminal

Sources/carton/Commands/Dev.swift

@@ -47,6 +47,9 @@ struct Dev: ParsableCommand {
   @Option(name: .shortAndLong, help: "Set the HTTP port the app will run on.")
   var port = 8080
 
+  @Flag(name: .long, help: "Skip automatically opening app in system browser.")
+  var skipAutoOpen = false
+
   static let configuration = CommandConfiguration(
     abstract: "Watch the current directory, host the app, rebuild on change."
   )
@@ -84,6 +87,7 @@ struct Dev: ParsableCommand {
       // swiftlint:disable:next force_try
       package: try! toolchain.package.get(),
       verbose: verbose,
+      skipAutoOpen: skipAutoOpen,
       terminal,
       port: port
     ).run()

Sources/carton/Server/Server.swift

@@ -39,6 +39,8 @@ final class Server {
   private let watcher: Watcher
   private var builder: ProcessRunner?
   private let app: Application
+  private let localURL: String
+  private let skipAutoOpen: Bool
 
   init(
     builderArguments: [String],
@@ -47,12 +49,16 @@ final class Server {
     customIndexContent: String?,
     package: SwiftToolchain.Package,
     verbose: Bool,
+    skipAutoOpen: Bool,
     _ terminal: InteractiveWriter,
     port: Int
   ) throws {
     watcher = try Watcher(pathsToWatch)
 
     var env = Environment(name: verbose ? "development" : "production", arguments: ["vapor"])
+    localURL = "http://127.0.0.1:\(port)/"
+    self.skipAutoOpen = skipAutoOpen
+
     try LoggingSystem.bootstrap(from: &env)
     app = Application(env)
     app.configure(
@@ -67,6 +73,8 @@ final class Server {
         self?.connections.remove($0)
       }
     )
+    // Listen to Vapor App lifecycle events
+    app.lifecycle.use(self)
 
     watcher.publisher
       .flatMap(maxPublishers: .max(1)) { changes -> AnyPublisher<String, Never> in
@@ -80,11 +88,11 @@ final class Server {
         return ProcessRunner(builderArguments, terminal)
           .publisher
           .handleEvents(receiveCompletion: { [weak self] in
-            guard case .finished = $0 else { return }
+            guard case .finished = $0, let self = self else { return }
 
             terminal.write("\nBuild completed successfully\n", inColor: .green, bold: false)
-            terminal.logLookup("The app is currently hosted at ", "http://127.0.0.1:\(port)/")
-            self?.connections.forEach { $0.send("reload") }
+            terminal.logLookup("The app is currently hosted at ", self.localURL)
+            self.connections.forEach { $0.send("reload") }
           })
           .catch { _ in Empty().eraseToAnyPublisher() }
           .eraseToAnyPublisher()
@@ -102,3 +110,35 @@ final class Server {
     }
   }
 }
+
+extension Server: LifecycleHandler {
+  public func didBoot(_ application: Application) throws {
+    guard !skipAutoOpen else { return }
+    openInSystemBrowser(url: localURL)
+  }
+
+  /// Attempts to open the specified URL string in system browser on macOS and Linux.
+  /// - Returns: true if launching command returns successfully.
+  @discardableResult
+  private func openInSystemBrowser(url: String) -> Bool {
+    #if os(macOS)
+    let openCommand = "open"
+    #elseif os(Linux)
+    let openCommand = "xdg-open"
+    #else
+    return false
+    #endif
+    let process = Process(
+      arguments: [openCommand, url],
+      outputRedirection: .none,
+      verbose: false,
+      startNewProcessGroup: true
+    )
+    do {
+      try process.launch()
+      return true
+    } catch {
+      return false
+    }
+  }
+}