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Rename Error to MCPError (#44)

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* Rename Error to MCPError

* Conform MCPError to Swift.Error

* Use unqualified Error instead of Swift.Error

* Use unqualified MCPError instead of MCP.MCPError

* Rename file back to Error.swift

* Introduce top-level MCP namespace with nested Error typealias to provide deprecation notice for existing usage of MCP.Error

* Fix markup for MCP enum warning
This commit is contained in:
Mattt 2025-04-03 05:25:00 -07:00 • committed by GitHub
commit 09da2a1c01
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GPG key ID: B5690EEEBB952194
10 changed files with 108 additions and 88 deletions
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34
Sources/MCP/Base/Error.swift
View file

@ -6,8 +6,24 @@ import Foundation
@preconcurrency import SystemPackage
#endif
/// Top-level namespace for backward compatibility
///
/// This is provided to allow existing code that uses `MCP.Error` to continue
/// to work without modification.
///
/// The MCPError type is now the recommended way to handle errors in MCP.
///
/// - Warning: This namespace is deprecated and will be removed in a future version.
public enum MCP {
/// Deprecated type alias for MCPError
@available(*, deprecated, renamed: "MCPError", message: "Use MCPError instead of MCP.Error")
public typealias Error = MCPError
}
// MARK: -
/// A model context protocol error.
public enum Error: Sendable {
public enum MCPError: Error, Sendable {
// Standard JSON-RPC 2.0 errors (-32700 to -32603)
case parseError(String?) // -32700
case invalidRequest(String?) // -32600
@ -20,7 +36,7 @@ public enum Error: Sendable {
// Transport specific errors
case connectionClosed
case transportError(Swift.Error)
case transportError(Error)
/// The JSON-RPC 2.0 error code
public var code: Int {
@ -37,7 +53,7 @@ public enum Error: Sendable {
}
/// Check if an error represents a "resource temporarily unavailable" condition
public static func isResourceTemporarilyUnavailable(_ error: Swift.Error) -> Bool {
public static func isResourceTemporarilyUnavailable(_ error: Error) -> Bool {
#if canImport(System)
if let errno = error as? System.Errno, errno == .resourceTemporarilyUnavailable {
return true
@ -53,7 +69,7 @@ public enum Error: Sendable {
// MARK: LocalizedError
extension Error: LocalizedError {
extension MCPError: LocalizedError {
public var errorDescription: String? {
switch self {
case .parseError(let detail):
@ -116,7 +132,7 @@ extension Error: LocalizedError {
// MARK: CustomDebugStringConvertible
extension Error: CustomDebugStringConvertible {
extension MCPError: CustomDebugStringConvertible {
public var debugDescription: String {
switch self {
case .transportError(let error):
@ -131,7 +147,7 @@ extension Error: CustomDebugStringConvertible {
// MARK: Codable
extension Error: Codable {
extension MCPError: Codable {
private enum CodingKeys: String, CodingKey {
case code, message, data
}
@ -199,15 +215,15 @@ extension Error: Codable {
// MARK: Equatable
extension Error: Equatable {
public static func == (lhs: Error, rhs: Error) -> Bool {
extension MCPError: Equatable {
public static func == (lhs: MCPError, rhs: MCPError) -> Bool {
lhs.code == rhs.code
}
}
// MARK: Hashable
extension Error: Hashable {
extension MCPError: Hashable {
public func hash(into hasher: inout Hasher) {
hasher.combine(code)
switch self {

8
Sources/MCP/Base/Messages.swift
View file

@ -60,7 +60,7 @@ extension Method {
}
/// Create a response with the given error.
public static func response(id: ID, error: Error) -> Response<Self> {
public static func response(id: ID, error: MCPError) -> Response<Self> {
Response(id: id, error: error)
}
}
@ -186,14 +186,14 @@ public struct Response<M: Method>: Hashable, Identifiable, Codable, Sendable {
/// The response ID.
public let id: ID
/// The response result.
public let result: Swift.Result<M.Result, Error>
public let result: Swift.Result<M.Result, MCPError>
public init(id: ID, result: M.Result) {
self.id = id
self.result = .success(result)
}
public init(id: ID, error: Error) {
public init(id: ID, error: MCPError) {
self.id = id
self.result = .failure(error)
}
@ -224,7 +224,7 @@ public struct Response<M: Method>: Hashable, Identifiable, Codable, Sendable {
id = try container.decode(ID.self, forKey: .id)
if let result = try? container.decode(M.Result.self, forKey: .result) {
self.result = .success(result)
} else if let error = try? container.decode(Error.self, forKey: .error) {
} else if let error = try? container.decode(MCPError.self, forKey: .error) {
self.result = .failure(error)
} else {
throw DecodingError.dataCorrupted(

54
Sources/MCP/Base/Transports.swift
View file

@ -23,7 +23,7 @@ public protocol Transport: Actor {
func send(_ data: Data) async throws
/// Receives data in an async sequence
func receive() -> AsyncThrowingStream<Data, Swift.Error>
func receive() -> AsyncThrowingStream<Data, Error>
}
/// Standard input/output transport implementation
@ -74,11 +74,11 @@ public actor StdioTransport: Transport {
private func setNonBlocking(fileDescriptor: FileDescriptor) throws {
let flags = fcntl(fileDescriptor.rawValue, F_GETFL)
guard flags >= 0 else {
throw Error.transportError(Errno.badFileDescriptor)
throw MCPError.transportError(Errno.badFileDescriptor)
}
let result = fcntl(fileDescriptor.rawValue, F_SETFL, flags | O_NONBLOCK)
guard result >= 0 else {
throw Error.transportError(Errno.badFileDescriptor)
throw MCPError.transportError(Errno.badFileDescriptor)
}
}
@ -110,7 +110,7 @@ public actor StdioTransport: Transport {
messageContinuation.yield(Data(messageData))
}
}
} catch let error where Error.isResourceTemporarilyUnavailable(error) {
} catch let error where MCPError.isResourceTemporarilyUnavailable(error) {
try? await Task.sleep(for: .milliseconds(10))
continue
} catch {
@ -133,7 +133,7 @@ public actor StdioTransport: Transport {
public func send(_ message: Data) async throws {
guard isConnected else {
throw Error.transportError(Errno.socketNotConnected)
throw MCPError.transportError(Errno.socketNotConnected)
}
// Add newline as delimiter
@ -149,16 +149,16 @@ public actor StdioTransport: Transport {
if written > 0 {
remaining = remaining.dropFirst(written)
}
} catch let error where Error.isResourceTemporarilyUnavailable(error) {
} catch let error where MCPError.isResourceTemporarilyUnavailable(error) {
try await Task.sleep(for: .milliseconds(10))
continue
} catch {
throw Error.transportError(error)
throw MCPError.transportError(error)
}
}
}
public func receive() -> AsyncThrowingStream<Data, Swift.Error> {
public func receive() -> AsyncThrowingStream<Data, Error> {
return AsyncThrowingStream { continuation in
Task {
for await message in messageStream {
@ -179,8 +179,8 @@ public actor StdioTransport: Transport {
public nonisolated let logger: Logger
private var isConnected = false
private let messageStream: AsyncThrowingStream<Data, Swift.Error>
private let messageContinuation: AsyncThrowingStream<Data, Swift.Error>.Continuation
private let messageStream: AsyncThrowingStream<Data, Error>
private let messageContinuation: AsyncThrowingStream<Data, Error>.Continuation
// Track connection state for continuations
private var connectionContinuationResumed = false
@ -195,7 +195,7 @@ public actor StdioTransport: Transport {
)
// Create message stream
var continuation: AsyncThrowingStream<Data, Swift.Error>.Continuation!
var continuation: AsyncThrowingStream<Data, Error>.Continuation!
self.messageStream = AsyncThrowingStream { continuation = $0 }
self.messageContinuation = continuation
}
@ -209,9 +209,9 @@ public actor StdioTransport: Transport {
// Wait for connection to be ready
try await withCheckedThrowingContinuation {
[weak self] (continuation: CheckedContinuation<Void, Swift.Error>) in
[weak self] (continuation: CheckedContinuation<Void, Error>) in
guard let self = self else {
continuation.resume(throwing: MCP.Error.internalError("Transport deallocated"))
continuation.resume(throwing: MCPError.internalError("Transport deallocated"))
return
}
@ -245,7 +245,7 @@ public actor StdioTransport: Transport {
}
}
private func handleConnectionReady(continuation: CheckedContinuation<Void, Swift.Error>)
private func handleConnectionReady(continuation: CheckedContinuation<Void, Error>)
async
{
if !connectionContinuationResumed {
@ -259,7 +259,7 @@ public actor StdioTransport: Transport {
}
private func handleConnectionFailed(
error: Swift.Error, continuation: CheckedContinuation<Void, Swift.Error>
error: Error, continuation: CheckedContinuation<Void, Error>
) async {
if !connectionContinuationResumed {
connectionContinuationResumed = true
@ -268,13 +268,13 @@ public actor StdioTransport: Transport {
}
}
private func handleConnectionCancelled(continuation: CheckedContinuation<Void, Swift.Error>)
private func handleConnectionCancelled(continuation: CheckedContinuation<Void, Error>)
async
{
if !connectionContinuationResumed {
connectionContinuationResumed = true
logger.warning("Connection cancelled")
continuation.resume(throwing: MCP.Error.internalError("Connection cancelled"))
continuation.resume(throwing: MCPError.internalError("Connection cancelled"))
}
}
@ -288,7 +288,7 @@ public actor StdioTransport: Transport {
public func send(_ message: Data) async throws {
guard isConnected else {
throw MCP.Error.internalError("Transport not connected")
throw MCPError.internalError("Transport not connected")
}
// Add newline as delimiter
@ -299,9 +299,9 @@ public actor StdioTransport: Transport {
var sendContinuationResumed = false
try await withCheckedThrowingContinuation {
[weak self] (continuation: CheckedContinuation<Void, Swift.Error>) in
[weak self] (continuation: CheckedContinuation<Void, Error>) in
guard let self = self else {
continuation.resume(throwing: MCP.Error.internalError("Transport deallocated"))
continuation.resume(throwing: MCPError.internalError("Transport deallocated"))
return
}
@ -316,7 +316,7 @@ public actor StdioTransport: Transport {
if let error = error {
self.logger.error("Send error: \(error)")
continuation.resume(
throwing: MCP.Error.internalError("Send error: \(error)"))
throwing: MCPError.internalError("Send error: \(error)"))
} else {
continuation.resume()
}
@ -326,7 +326,7 @@ public actor StdioTransport: Transport {
}
}
public func receive() -> AsyncThrowingStream<Data, Swift.Error> {
public func receive() -> AsyncThrowingStream<Data, Error> {
return AsyncThrowingStream { continuation in
Task {
do {
@ -363,7 +363,7 @@ public actor StdioTransport: Transport {
} catch let error as NWError {
if !Task.isCancelled {
logger.error("Network error occurred", metadata: ["error": "\(error)"])
messageContinuation.finish(throwing: MCP.Error.transportError(error))
messageContinuation.finish(throwing: MCPError.transportError(error))
}
break
} catch {
@ -382,9 +382,9 @@ public actor StdioTransport: Transport {
var receiveContinuationResumed = false
return try await withCheckedThrowingContinuation {
[weak self] (continuation: CheckedContinuation<Data, Swift.Error>) in
[weak self] (continuation: CheckedContinuation<Data, Error>) in
guard let self = self else {
continuation.resume(throwing: MCP.Error.internalError("Transport deallocated"))
continuation.resume(throwing: MCPError.internalError("Transport deallocated"))
return
}
@ -394,12 +394,12 @@ public actor StdioTransport: Transport {
if !receiveContinuationResumed {
receiveContinuationResumed = true
if let error = error {
continuation.resume(throwing: MCP.Error.transportError(error))
continuation.resume(throwing: MCPError.transportError(error))
} else if let content = content {
continuation.resume(returning: content)
} else {
continuation.resume(
throwing: MCP.Error.internalError("No data received"))
throwing: MCPError.internalError("No data received"))
}
}
}

20
Sources/MCP/Client/Client.swift
View file

@ -112,16 +112,16 @@ public actor Client {
private var task: Task<Void, Never>?
/// An error indicating a type mismatch when decoding a pending request
private struct TypeMismatchError: Swift.Error {}
private struct TypeMismatchError: Error {}
/// A pending request with a continuation for the result
private struct PendingRequest<T> {
let continuation: CheckedContinuation<T, Swift.Error>
let continuation: CheckedContinuation<T, Error>
}
/// A type-erased pending request
private struct AnyPendingRequest {
private let _resume: (Result<Any, Swift.Error>) -> Void
private let _resume: (Result<Any, Error>) -> Void
init<T: Sendable & Decodable>(_ request: PendingRequest<T>) {
_resume = { result in
@ -146,7 +146,7 @@ public actor Client {
_resume(.success(value))
}
func resume(throwing error: Swift.Error) {
func resume(throwing error: Error) {
_resume(.failure(error))
}
}
@ -201,7 +201,7 @@ public actor Client {
"Unexpected message received by client", metadata: metadata)
}
}
} catch let error where Error.isResourceTemporarilyUnavailable(error) {
} catch let error where MCPError.isResourceTemporarilyUnavailable(error) {
try? await Task.sleep(for: .milliseconds(10))
continue
} catch {
@ -217,7 +217,7 @@ public actor Client {
public func disconnect() async {
// Cancel all pending requests
for (id, request) in pendingRequests {
request.resume(throwing: Error.internalError("Client disconnected"))
request.resume(throwing: MCPError.internalError("Client disconnected"))
pendingRequests.removeValue(forKey: id)
}
@ -247,7 +247,7 @@ public actor Client {
/// Send a request and receive its response
public func send<M: Method>(_ request: Request<M>) async throws -> M.Result {
guard let connection = connection else {
throw Error.internalError("Client connection not initialized")
throw MCPError.internalError("Client connection not initialized")
}
let requestData = try JSONEncoder().encode(request)
@ -274,7 +274,7 @@ public actor Client {
private func addPendingRequest<T: Sendable & Decodable>(
id: ID,
continuation: CheckedContinuation<T, Swift.Error>,
continuation: CheckedContinuation<T, Error>,
type: T.Type
) {
pendingRequests[id] = AnyPendingRequest(PendingRequest(continuation: continuation))
@ -439,10 +439,10 @@ public actor Client {
{
if configuration.strict {
guard let capabilities = serverCapabilities else {
throw Error.methodNotFound("Server capabilities not initialized")
throw MCPError.methodNotFound("Server capabilities not initialized")
}
guard capabilities[keyPath: keyPath] != nil else {
throw Error.methodNotFound("\(name) is not supported by the server")
throw MCPError.methodNotFound("\(name) is not supported by the server")
}
}
}

24
Sources/MCP/Server/Server.swift
View file

@ -195,9 +195,9 @@ public actor Server {
requestID = .number(intValue)
}
}
throw Error.parseError("Invalid message format")
throw MCPError.parseError("Invalid message format")
}
} catch let error where Error.isResourceTemporarilyUnavailable(error) {
} catch let error where MCPError.isResourceTemporarilyUnavailable(error) {
// Resource temporarily unavailable, retry after a short delay
try? await Task.sleep(for: .milliseconds(10))
continue
@ -206,8 +206,8 @@ public actor Server {
"Error processing message", metadata: ["error": "\(error)"])
let response = AnyMethod.response(
id: requestID ?? .random,
error: error as? Error
?? Error.internalError(error.localizedDescription)
error: error as? MCPError
?? MCPError.internalError(error.localizedDescription)
)
try? await send(response)
}
@ -265,7 +265,7 @@ public actor Server {
/// Send a response to a request
public func send<M: Method>(_ response: Response<M>) async throws {
guard let connection = connection else {
throw Error.internalError("Server connection not initialized")
throw MCPError.internalError("Server connection not initialized")
}
let encoder = JSONEncoder()
@ -278,7 +278,7 @@ public actor Server {
/// Send a notification to connected clients
public func notify<N: Notification>(_ notification: Message<N>) async throws {
guard let connection = connection else {
throw Error.internalError("Server connection not initialized")
throw MCPError.internalError("Server connection not initialized")
}
let encoder = JSONEncoder()
@ -311,7 +311,7 @@ public actor Server {
// Find handler for method name
guard let handler = methodHandlers[request.method] else {
let error = Error.methodNotFound("Unknown method: \(request.method)")
let error = MCPError.methodNotFound("Unknown method: \(request.method)")
let response = AnyMethod.response(id: request.id, error: error)
try await send(response)
throw error
@ -322,7 +322,7 @@ public actor Server {
let response = try await handler(request)
try await send(response)
} catch {
let mcpError = error as? Error ?? Error.internalError(error.localizedDescription)
let mcpError = error as? MCPError ?? MCPError.internalError(error.localizedDescription)
let response = AnyMethod.response(id: request.id, error: mcpError)
try await send(response)
throw error
@ -361,7 +361,7 @@ public actor Server {
private func checkInitialized() throws {
guard isInitialized else {
throw Error.invalidRequest("Server is not initialized")
throw MCPError.invalidRequest("Server is not initialized")
}
}
@ -371,16 +371,16 @@ public actor Server {
// Initialize
withMethodHandler(Initialize.self) { [weak self] params in
guard let self = self else {
throw Error.internalError("Server was deallocated")
throw MCPError.internalError("Server was deallocated")
}
guard await !self.isInitialized else {
throw Error.invalidRequest("Server is already initialized")
throw MCPError.invalidRequest("Server is already initialized")
}
// Validate protocol version
guard Version.latest == params.protocolVersion else {
throw Error.invalidRequest(
throw MCPError.invalidRequest(
"Unsupported protocol version: \(params.protocolVersion)")
}

20
Tests/MCPTests/ClientTests.swift
View file

@ -90,8 +90,8 @@ struct ClientTests {
do {
try await client.connect(transport: transport)
#expect(Bool(false), "Expected connection to fail")
} catch let error as Error {
if case Error.transportError = error {
} catch let error as MCPError {
if case MCPError.transportError = error {
#expect(Bool(true))
} else {
#expect(Bool(false), "Expected transport error")
@ -112,8 +112,8 @@ struct ClientTests {
do {
try await client.ping()
#expect(Bool(false), "Expected ping to fail")
} catch let error as Error {
if case Error.transportError = error {
} catch let error as MCPError {
if case MCPError.transportError = error {
#expect(Bool(true))
} else {
#expect(Bool(false), "Expected transport error")
@ -132,12 +132,12 @@ struct ClientTests {
try await client.connect(transport: transport)
// Create a task for listPrompts
let promptsTask = Task<Void, Swift.Error> {
let promptsTask = Task<Void, Error> {
do {
_ = try await client.listPrompts()
#expect(Bool(false), "Expected listPrompts to fail in strict mode")
} catch let error as Error {
if case Error.methodNotFound = error {
} catch let error as MCPError {
if case MCPError.methodNotFound = error {
#expect(Bool(true))
} else {
#expect(Bool(false), "Expected methodNotFound error, got \(error)")
@ -185,7 +185,7 @@ struct ClientTests {
// Create an error response with the same ID
let errorResponse = Response<ListPrompts>(
id: decodedRequest.id,
error: Error.methodNotFound("Test: Prompts capability not available")
error: MCPError.methodNotFound("Test: Prompts capability not available")
)
try await transport.queue(response: errorResponse)
@ -193,8 +193,8 @@ struct ClientTests {
do {
_ = try await client.listPrompts()
#expect(Bool(false), "Expected listPrompts to fail in non-strict mode")
} catch let error as Error {
if case Error.methodNotFound = error {
} catch let error as MCPError {
if case MCPError.methodNotFound = error {
#expect(Bool(true))
} else {
#expect(Bool(false), "Expected methodNotFound error, got \(error)")

22
Tests/MCPTests/Helpers/MockTransport.swift
View file

@ -1,4 +1,8 @@
import Foundation
import class Foundation.JSONEncoder
import class Foundation.JSONDecoder
import struct Foundation.Data
import struct Foundation.POSIXError
import Logging
@testable import MCP
@ -26,7 +30,7 @@ actor MockTransport: Transport {
private var dataToReceive: [Data] = []
private(set) var receivedMessages: [String] = []
private var dataStreamContinuation: AsyncThrowingStream<Data, Swift.Error>.Continuation?
private var dataStreamContinuation: AsyncThrowingStream<Data, Error>.Continuation?
var shouldFailConnect = false
var shouldFailSend = false
@ -37,7 +41,7 @@ actor MockTransport: Transport {
public func connect() async throws {
if shouldFailConnect {
throw Error.transportError(POSIXError(.ECONNREFUSED))
throw MCPError.transportError(POSIXError(.ECONNREFUSED))
}
isConnected = true
}
@ -50,13 +54,13 @@ actor MockTransport: Transport {
public func send(_ message: Data) async throws {
if shouldFailSend {
throw Error.transportError(POSIXError(.EIO))
throw MCPError.transportError(POSIXError(.EIO))
}
sentData.append(message)
}
public func receive() -> AsyncThrowingStream<Data, Swift.Error> {
return AsyncThrowingStream<Data, Swift.Error> { continuation in
public func receive() -> AsyncThrowingStream<Data, Error> {
return AsyncThrowingStream<Data, Error> { continuation in
dataStreamContinuation = continuation
for message in dataToReceive {
continuation.yield(message)
@ -76,7 +80,7 @@ actor MockTransport: Transport {
shouldFailSend = shouldFail
}
func queue<M: MCP.Method>(request: Request<M>) throws {
func queue<M: Method>(request: Request<M>) throws {
let data = try encoder.encode(request)
if let continuation = dataStreamContinuation {
continuation.yield(data)
@ -85,12 +89,12 @@ actor MockTransport: Transport {
}
}
func queue<M: MCP.Method>(response: Response<M>) throws {
func queue<M: Method>(response: Response<M>) throws {
let data = try encoder.encode(response)
dataToReceive.append(data)
}
func queue<N: MCP.Notification>(notification: Message<N>) throws {
func queue<N: Notification>(notification: Message<N>) throws {
let data = try encoder.encode(notification)
dataToReceive.append(data)
}

4
Tests/MCPTests/ResponseTests.swift
View file

@ -43,7 +43,7 @@ struct ResponseTests {
@Test("Error response initialization and encoding")
func testErrorResponse() throws {
let id: ID = "test-id"
let error = MCP.Error.parseError(nil)
let error = MCPError.parseError(nil)
let response = Response<TestMethod>(id: id, error: error)
let encoder = JSONEncoder()
@ -65,7 +65,7 @@ struct ResponseTests {
@Test("Error response with detail")
func testErrorResponseWithDetail() throws {
let id: ID = "test-id"
let error = MCP.Error.parseError("Invalid syntax")
let error = MCPError.parseError("Invalid syntax")
let response = Response<TestMethod>(id: id, error: error)
let encoder = JSONEncoder()

2
Tests/MCPTests/ServerTests.swift
View file

@ -109,7 +109,7 @@ struct ServerTests {
try await server.start(transport: transport) { clientInfo, _ in
if clientInfo.name == "BlockedClient" {
throw Error.invalidRequest("Client not allowed")
throw MCPError.invalidRequest("Client not allowed")
}
}

8
Tests/MCPTests/TransportTests.swift
View file

@ -57,7 +57,7 @@ struct StdioTransportTests {
try writer.close()
// Start receiving messages
let stream: AsyncThrowingStream<Data, Swift.Error> = await transport.receive()
let stream: AsyncThrowingStream<Data, Error> = await transport.receive()
var iterator = stream.makeAsyncIterator()
// Get first message
@ -79,7 +79,7 @@ struct StdioTransportTests {
try writer.writeAll(invalidJSON.data(using: .utf8)!)
try writer.close()
let stream: AsyncThrowingStream<Data, Swift.Error> = await transport.receive()
let stream: AsyncThrowingStream<Data, Error> = await transport.receive()
var iterator = stream.makeAsyncIterator()
_ = try await iterator.next()
@ -100,7 +100,7 @@ struct StdioTransportTests {
try await transport.connect()
#expect(Bool(false), "Expected connect to throw an error")
} catch {
#expect(error is MCP.Error)
#expect(error is MCPError)
}
await transport.disconnect()
@ -119,7 +119,7 @@ struct StdioTransportTests {
try await transport.connect()
#expect(Bool(false), "Expected connect to throw an error")
} catch {
#expect(error is MCP.Error)
#expect(error is MCPError)
}
await transport.disconnect()