feat: Incremental builds

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.10
+// swift-tools-version:6.0
 
 import PackageDescription
 

README.md

@@ -18,6 +18,14 @@ $ brew install loopwerk/tap/saga
 $ mint install loopwerk/saga-cli
 ```
 
+**From source:**
+
+```shell-session
+$ git clone https://github.com/loopwerk/saga-cli.git
+$ cd saga-cli
+$ swift package experimental-install
+```
+
 > **Migrating from an older version?** The CLI previously lived inside the [Saga](https://github.com/loopwerk/Saga) repository. If you installed via Mint using `mint install loopwerk/Saga`, switch to `mint install loopwerk/saga-cli`.
 
 ## Commands
@@ -44,30 +52,18 @@ $ saga build
 
 ### `saga dev`
 
-Start a development server with file watching and auto-reload:
+Start a development server with auto-reload on port 3000:
 
 ```
 $ saga dev
+$ saga dev --port 8080
 ```
 
-Options:
-
-| Flag             | Default              | Description                                    |
-| ---------------- | -------------------- | ---------------------------------------------- |
-| `--watch`, `-w`  | `content`, `Sources` | Folders to watch for changes (repeatable)      |
-| `--output`, `-o` | `deploy`             | Output folder for the built site               |
-| `--port`, `-p`   | `3000`               | Port for the development server                |
-| `--ignore`, `-i` |                      | Glob patterns for files to ignore (repeatable) |
-
-Example with custom options:
-
-```
-$ saga dev --watch content --watch Sources --output deploy --port 8080 --ignore "*.tmp" --ignore "drafts/*"
-```
+> **Note:** saga-cli 2.x requires Saga 3.x or later.
 
 ## Requirements
 
-Swift 5.5+ and macOS 12+.
+Swift 6.0+ and macOS 14+ or Linux.
 
 ## License
 

Sources/SagaCLI/BuildCommand.swift

@@ -7,7 +7,7 @@ struct Build: ParsableCommand {
   )
 
   func run() throws {
-    print("Building site...")
+    log("Building site...")
 
     let process = Process()
     process.executableURL = URL(fileURLWithPath: "/usr/bin/env")
@@ -17,7 +17,7 @@ struct Build: ParsableCommand {
     process.waitUntilExit()
 
     if process.terminationStatus == 0 {
-      print("Build complete.")
+      log("Build complete.")
     } else {
       throw ExitCode(process.terminationStatus)
     }

Sources/SagaCLI/DevCommand.swift

@@ -7,18 +7,9 @@ struct Dev: ParsableCommand {
     abstract: "Build, watch for changes, and serve the site with auto-reload."
   )
 
-  @Option(name: .shortAndLong, help: "Folder to watch for changes. Can be specified multiple times.")
-  var watch: [String] = ["content", "Sources"]
-
-  @Option(name: .shortAndLong, help: "Output folder for the built site.")
-  var output: String = "deploy"
-
   @Option(name: .shortAndLong, help: "Port for the development server.")
   var port: Int = 3000
 
-  @Option(name: .shortAndLong, help: "Glob pattern for files to ignore. Can be specified multiple times.")
-  var ignore: [String] = []
-
   func run() throws {
     // Create a fresh cache directory for this dev session
     let cachePath = Path.current + ".build/saga-cache"
@@ -27,19 +18,79 @@ struct Dev: ParsableCommand {
     }
     try cachePath.mkpath()
 
-    print("Building site...")
-    let buildResult = runBuild(cachePath: cachePath)
-    if !buildResult {
-      print("Initial build failed, starting server anyway...")
+    // Find the executable product name from Package.swift
+    guard let productName = findExecutableProduct() else {
+      print("Could not find an executable product in Package.swift")
+      throw ExitCode.failure
+    }
+
+    // Initial build
+    log("Building site...")
+    guard swiftBuild() else {
+      log("Initial build failed.")
+      throw ExitCode.failure
+    }
+
+    let coordinator = DevCoordinator(productName: productName, cachePath: cachePath, port: port)
+    try coordinator.start()
+  }
+}
+
+/// Manages the dev server lifecycle: site process, HTTP server, signal handling.
+private final class DevCoordinator: @unchecked Sendable {
+  let productName: String
+  let cachePath: Path
+  let port: Int
+  var siteProcess: Process?
+  var server: DevServer?
+
+  init(productName: String, cachePath: Path, port: Int) {
+    self.productName = productName
+    self.cachePath = cachePath
+    self.port = port
+  }
+
+  func start() throws {
+    // Set up SIGUSR2 handler — Saga signals us when a build completes so we can reload browsers
+    signal(SIGUSR2, SIG_IGN)
+    let sigusr2Source = DispatchSource.makeSignalSource(signal: SIGUSR2, queue: DispatchQueue(label: "Saga.Signal"))
+    sigusr2Source.setEventHandler { [weak self] in self?.server?.sendReload() }
+    sigusr2Source.resume()
+
+    // Launch the site process. Saga watches its own files and rebuilds internally.
+    // Exit code 42 means "Swift source changed, recompile me".
+    siteProcess = launchSiteProcess(productName: productName, cachePath: cachePath)
+    guard siteProcess != nil else {
+      log("Failed to launch site process.")
+      throw ExitCode.failure
+    }
+
+    // Wait for the initial build to complete (SIGUSR2 or process exit)
+    let initialBuild = DispatchSemaphore(value: 0)
+    siteProcess?.terminationHandler = { _ in initialBuild.signal() }
+    let initialSigusr2 = DispatchSource.makeSignalSource(signal: SIGUSR2, queue: DispatchQueue(label: "Saga.InitialBuild"))
+    initialSigusr2.setEventHandler { initialBuild.signal() }
+    initialSigusr2.resume()
+    initialBuild.wait()
+    initialSigusr2.cancel()
+    siteProcess?.terminationHandler = nil
+
+    // Read the config file written by Saga to detect output path.
+    // If the config file doesn't exist, this is a Saga 2 site which is not supported.
+    guard let config = readSagaConfig() else {
+      log("This version of saga-cli requires Saga 3.x or later.")
+      siteProcess?.terminate()
+      throw ExitCode.failure
     }
 
     // Start the dev server
-    let server = DevServer(outputPath: output, port: port)
+    let devServer = DevServer(outputPath: config.output, port: port)
+    server = devServer
 
     let serverQueue = DispatchQueue(label: "Saga.DevServer")
     serverQueue.async {
       do {
-        try server.start()
+        try devServer.start()
       } catch {
         print("Failed to start server: \(error)")
         Foundation.exit(1)
@@ -48,102 +99,46 @@ struct Dev: ParsableCommand {
 
     // Give the server a moment to start
     Thread.sleep(forTimeInterval: 0.5)
-    print("Development server running at http://localhost:\(port)/")
+    log("Development server running at http://localhost:\(port)/")
 
     // Open the browser
     openBrowser(url: "http://localhost:\(port)/")
 
-    // Turn watch folders into full paths
-    let currentPath = FileManager.default.currentDirectoryPath
-    let paths = watch.map { folder -> String in
-      if folder.hasPrefix("/") {
-        return folder
-      }
-      return currentPath + "/" + folder
-    }
-
-    let defaultIgnorePatterns = [".DS_Store"]
-
-    // Start monitoring
-    if !ignore.isEmpty {
-      print("Ignoring patterns: \(ignore.joined(separator: ", "))")
-    }
-
-    var isRebuilding = false
-    let rebuildLock = NSLock()
-
-    let folderMonitor = FolderMonitor(paths: paths, ignoredPatterns: defaultIgnorePatterns + ignore) {
-      rebuildLock.lock()
-      guard !isRebuilding else {
-        rebuildLock.unlock()
-        return
-      }
-      isRebuilding = true
-      rebuildLock.unlock()
-
-      print("Change detected, rebuilding...")
-      let success = runBuild(cachePath: cachePath)
-      if success {
-        print("Rebuild complete.")
-        server.sendReload()
-      } else {
-        print("Rebuild failed.")
-      }
-
-      rebuildLock.lock()
-      isRebuilding = false
-      rebuildLock.unlock()
-    }
-
     // Handle Ctrl+C shutdown
-    let signalsQueue = DispatchQueue(label: "Saga.Signals")
-    let sigintSrc = DispatchSource.makeSignalSource(signal: SIGINT, queue: signalsQueue)
-    sigintSrc.setEventHandler {
+    let sigintSrc = DispatchSource.makeSignalSource(signal: SIGINT, queue: DispatchQueue(label: "Saga.Signals"))
+    sigintSrc.setEventHandler { [weak self] in
       print("\nShutting down...")
-      server.stop()
+      self?.siteProcess?.terminate()
+      self?.server?.stop()
       Foundation.exit(0)
     }
     sigintSrc.resume()
     signal(SIGINT, SIG_IGN)
 
-    print("Watching for changes in: \(watch.joined(separator: ", "))")
+    // Watch for process exits. Exit code 42 = Swift source changed, recompile and relaunch.
+    if let process = siteProcess {
+      watchProcess(process)
+    }
 
-    // Prevent folderMonitor from being deallocated
-    withExtendedLifetime(folderMonitor) {
-      // Keep running
+    withExtendedLifetime((sigusr2Source, sigintSrc)) {
       dispatchMain()
     }
   }
 
-  private func runBuild(cachePath: Path) -> Bool {
-    let process = Process()
-    process.executableURL = URL(fileURLWithPath: "/usr/bin/env")
-    process.arguments = ["swift", "run"]
-    process.currentDirectoryURL = URL(fileURLWithPath: FileManager.default.currentDirectoryPath)
-
-    var env = ProcessInfo.processInfo.environment
-    env["SAGA_DEV"] = "1"
-    env["SAGA_CACHE_DIR"] = cachePath.string
-    process.environment = env
-
-    do {
-      try process.run()
-      process.waitUntilExit()
-      return process.terminationStatus == 0
-    } catch {
-      print("Build error: \(error)")
-      return false
-    }
-  }
+  func watchProcess(_ process: Process) {
+    process.terminationHandler = { [weak self] terminatedProcess in
+      guard let self, terminatedProcess.terminationStatus == 42 else { return }
+
+      log("Source code changed, recompiling...")
+      guard swiftBuild() else {
+        log("Build failed")
+        return
+      }
 
-  private func openBrowser(url: String) {
-    #if os(macOS)
-      Process.launchedProcess(launchPath: "/usr/bin/open", arguments: [url])
-    #elseif os(Linux)
-      let process = Process()
-      process.executableURL = URL(fileURLWithPath: "/usr/bin/env")
-      process.arguments = ["xdg-open", url]
-      try? process.run()
-    #endif
+      self.siteProcess = launchSiteProcess(productName: self.productName, cachePath: self.cachePath)
+      if let newProcess = self.siteProcess {
+        self.watchProcess(newProcess)
+      }
+    }
   }
 }

Sources/SagaCLI/DevServer.swift

@@ -3,7 +3,7 @@ import NIOCore
 import NIOHTTP1
 import NIOPosix
 
-final class DevServer {
+final class DevServer: @unchecked Sendable {
   private let outputPath: String
   private let port: Int
   private let group: MultiThreadedEventLoopGroup
@@ -73,7 +73,7 @@ final class SSEConnectionStore: @unchecked Sendable {
   }
 }
 
-private final class HTTPHandler: ChannelInboundHandler {
+private final class HTTPHandler: ChannelInboundHandler, @unchecked Sendable {
   typealias InboundIn = HTTPServerRequestPart
   typealias OutboundOut = HTTPServerResponsePart
 
@@ -152,10 +152,11 @@ private final class HTTPHandler: ChannelInboundHandler {
     let head = HTTPResponseHead(version: .http1_1, status: .ok, headers: headers)
     context.writeAndFlush(wrapOutboundOut(.head(head)), promise: nil)
 
-    sseConnections.add(context.channel)
+    let channel = context.channel
+    sseConnections.add(channel)
 
-    context.channel.closeFuture.whenComplete { [weak self] _ in
-      self?.sseConnections.remove(context.channel)
+    channel.closeFuture.whenComplete { [weak self] _ in
+      self?.sseConnections.remove(channel)
     }
   }