Show stdout/stderr from Wasm in terminal (#472)

Sources/CartonKit/Server/Server.swift

@@ -238,9 +238,14 @@ public actor Server {
           let environment =
             head.headers["User-Agent"].compactMap(DestinationEnvironment.init).first
             ?? .other
-          let handler = await ServerWebSocketHandler(
+          let handler = ServerWebSocketHandler(
             configuration: ServerWebSocketHandler.Configuration(
-              onText: self.createWebSocketTextHandler(in: environment, terminal: self.configuration.terminal)
+              onText: { [weak self] (text) in
+                self?.webSocketTextHandler(text: text, environment: environment)
+              },
+              onBinary: { [weak self] (data) in
+                self?.webSocketBinaryHandler(data: data)
+              }
             )
           )
           await self.add(connection: Connection(channel: channel))
@@ -329,13 +334,11 @@ public actor Server {
 }
 
 extension Server {
-  /// Returns a handler that responds to WebSocket messages coming from the browser.
-  func createWebSocketTextHandler(
-    in environment: DestinationEnvironment,
-    terminal: InteractiveWriter
-  ) -> @Sendable (String) -> Void {
-    { [weak self] text in
-      guard let self = self else { return }
+  /// Respond to WebSocket messages coming from the browser.
+  nonisolated func webSocketTextHandler(
+    text: String,
+    environment: DestinationEnvironment
+  ) {
     guard
       let data = text.data(using: .utf8),
       let event = try? self.decoder.decode(Event.self, from: data)
@@ -343,6 +346,8 @@ extension Server {
       return
     }
 
+    let terminal = self.configuration.terminal
+
     switch event {
     case let .stackTrace(rawStackTrace):
       if let stackTrace = rawStackTrace.parsedStackTrace(in: environment) {
@@ -374,6 +379,44 @@ extension Server {
       Task { await self.stopTest(hadError: true) }
     }
   }
+
+  private static func decodeLines(data: Data) -> [String] {
+    let text = String(decoding: data, as: UTF8.self)
+    return text.components(separatedBy: .newlines)
+  }
+
+  nonisolated func webSocketBinaryHandler(data: Data) {
+    let terminal = self.configuration.terminal
+
+    if data.count < 2 {
+      return
+    }
+
+    var kind: UInt16 = 0
+    _ = withUnsafeMutableBytes(of: &kind) { (buffer) in
+      data.copyBytes(to: buffer, from: 0..<2)
+    }
+    kind = UInt16(littleEndian: kind)
+
+    switch kind {
+    case 1001:
+      // stdout
+      let chunk = data.subdata(in: 2..<data.count)
+      if chunk.isEmpty { return }
+
+      for line in Self.decodeLines(data: chunk) {
+        terminal.write("stdout: " + line + "\n")
+      }
+    case 1002:
+      // stderr
+      let chunk = data.subdata(in: 2..<data.count)
+      if chunk.isEmpty { return }
+
+      for line in Self.decodeLines(data: chunk) {
+        terminal.write("stderr: " + line + "\n", inColor: .red)
+      }
+    default: break
+    }
   }
 }
 

Sources/CartonKit/Server/ServerWebSocketHandler.swift

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+import Foundation
 import NIO
 import NIOWebSocket
 
@@ -20,7 +21,8 @@ final class ServerWebSocketHandler: ChannelInboundHandler {
   typealias OutboundOut = WebSocketFrame
 
   struct Configuration {
-    let onText: @Sendable (String) -> Void
+    var onText: @Sendable (String) -> Void
+    var onBinary: @Sendable (Data) -> Void
   }
 
   private var awaitingClose: Bool = false
@@ -43,7 +45,11 @@ final class ServerWebSocketHandler: ChannelInboundHandler {
       var data = frame.unmaskedData
       let text = data.readString(length: data.readableBytes) ?? ""
       self.configuration.onText(text)
-    case .binary, .continuation, .pong:
+    case .binary:
+      let nioData = frame.unmaskedData
+      let data = Data(nioData.readableBytesView)
+      self.configuration.onBinary(data)
+    case .continuation, .pong:
       // We ignore these frames.
       break
     default:

Tests/Fixtures/DevServerTestApp/Sources/app/main.swift

@@ -1 +1,16 @@
-print("hello dev server")
+#if os(WASI)
+import WASILibc
+typealias FILEPointer = OpaquePointer
+#else
+import Darwin
+typealias FILEPointer = UnsafeMutablePointer<FILE>
+#endif
+
+func fputs(_ string: String, file: FILEPointer) {
+    _ = string.withCString { (cstr) in
+        fputs(cstr, file)
+    }
+}
+
+fputs("hello stdout\n", file: stdout)
+fputs("hello stderr\n", file: stderr)

entrypoint/dev.ts

@@ -44,9 +44,29 @@ const startWasiTask = async () => {
 
   const wasmRunner = WasmRunner(
     {
+      onStdout(chunk) {
+        const kindBuffer = new ArrayBuffer(2);
+        new DataView(kindBuffer).setUint16(0, 1001, true);
+
+        const buffer = new Uint8Array(2 + chunk.length);
+        buffer.set(new Uint8Array(kindBuffer), 0);
+        buffer.set(chunk, 2);
+
+        socket.send(buffer);
+      },
       onStdoutLine(line) {
         console.log(line);
       },
+      onStderr(chunk) {
+        const kindBuffer = new ArrayBuffer(2);
+        new DataView(kindBuffer).setUint16(0, 1002, true);
+
+        const buffer = new Uint8Array(2 + chunk.length);
+        buffer.set(new Uint8Array(kindBuffer), 0);
+        buffer.set(chunk, 2);
+
+        socket.send(buffer);
+      },
       onStderrLine(line) {
         console.error(line);
       }