Make closures sendable to fix compiler errors in Swift 5

Author: mattt

Sources/MCP/Base/Transports.swift

@@ -298,31 +298,20 @@ public actor StdioTransport: Transport {
                 throw MCP.Error.internalError("Failed to encode message")
             }
 
-            // Use a local actor-isolated variable to track continuation state
-            var sendContinuationResumed = false
-
             try await withCheckedThrowingContinuation {
-                [weak self] (continuation: CheckedContinuation<Void, Swift.Error>) in
-                guard let self = self else {
-                    continuation.resume(throwing: MCP.Error.internalError("Transport deallocated"))
-                    return
-                }
-
+                @Sendable (continuation: CheckedContinuation<Void, Swift.Error>) in
                 connection.send(
                     content: data,
-                    completion: .contentProcessed { [weak self] error in
+                    completion: .contentProcessed { @Sendable [weak self] error in
                         guard let self = self else { return }
 
-                        Task { @MainActor in
-                            if !sendContinuationResumed {
-                                sendContinuationResumed = true
-                                if let error = error {
-                                    self.logger.error("Send error: \(error)")
-                                    continuation.resume(
-                                        throwing: MCP.Error.internalError("Send error: \(error)"))
-                                } else {
-                                    continuation.resume()
-                                }
+                        Task {
+                            if let error = error {
+                                self.logger.error("Send error: \(error)")
+                                continuation.resume(
+                                    throwing: MCP.Error.internalError("Send error: \(error)"))
+                            } else {
+                                continuation.resume()
                             }
                         }
                     })
@@ -383,28 +372,19 @@ public actor StdioTransport: Transport {
         }
 
         private func receiveData() async throws -> Data {
-            var receiveContinuationResumed = false
-
-            return try await withCheckedThrowingContinuation {
-                [weak self] (continuation: CheckedContinuation<Data, Swift.Error>) in
-                guard let self = self else {
-                    continuation.resume(throwing: MCP.Error.internalError("Transport deallocated"))
-                    return
-                }
-
+            try await withCheckedThrowingContinuation {
+                @Sendable (continuation: CheckedContinuation<Data, Swift.Error>) in
                 connection.receive(minimumIncompleteLength: 1, maximumLength: 65536) {
+                    @Sendable
                     content, _, _, error in
-                    Task { @MainActor in
-                        if !receiveContinuationResumed {
-                            receiveContinuationResumed = true
-                            if let error = error {
-                                continuation.resume(throwing: MCP.Error.transportError(error))
-                            } else if let content = content {
-                                continuation.resume(returning: content)
-                            } else {
-                                continuation.resume(
-                                    throwing: MCP.Error.internalError("No data received"))
-                            }
+                    Task {
+                        if let error = error {
+                            continuation.resume(throwing: MCP.Error.transportError(error))
+                        } else if let content = content {
+                            continuation.resume(returning: content)
+                        } else {
+                            continuation.resume(
+                                throwing: MCP.Error.internalError("No data received"))
                         }
                     }
                 }