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Avoid race starting SseResponseStreamTransport #91

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Merged
merged 1 commit into from
Mar 25, 2025
Merged

Avoid race starting SseResponseStreamTransport #91

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9 changes: 6 additions & 3 deletions src/ModelContextProtocol/Protocol/Transport/SseResponseStreamTransport.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@ public sealed class SseResponseStreamTransport(Stream sseResponseStream) : ITran
private Utf8JsonWriter? _jsonWriter;

/// <inheritdoc/>
public bool IsConnected => _sseWriteTask?.IsCompleted == false;
public bool IsConnected { get; private set; }

/// <summary>
/// Starts the transport and writes the JSON-RPC messages sent via <see cref="SendMessageAsync(IJsonRpcMessage, CancellationToken)"/>
Expand All @@ -41,6 +41,8 @@ void WriteJsonRpcMessageToBuffer(SseItem<IJsonRpcMessage?> item, IBufferWriter<b
JsonSerializer.Serialize(GetUtf8JsonWriter(writer), item.Data, McpJsonUtilities.DefaultOptions.GetTypeInfo<IJsonRpcMessage?>());
}

IsConnected = true;

// The very first SSE event isn't really an IJsonRpcMessage, but there's no API to write a single item of a different type,
// so we fib and special-case the "endpoint" event type in the formatter.
_outgoingSseChannel.Writer.TryWrite(new SseItem<IJsonRpcMessage?>(null, "endpoint"));
Expand All @@ -55,6 +57,7 @@ void WriteJsonRpcMessageToBuffer(SseItem<IJsonRpcMessage?> item, IBufferWriter<b
/// <inheritdoc/>
public ValueTask DisposeAsync()
{
IsConnected = false;
_incomingChannel.Writer.TryComplete();
_outgoingSseChannel.Writer.TryComplete();
return new ValueTask(_sseWriteTask ?? Task.CompletedTask);
Expand All @@ -63,7 +66,7 @@ public ValueTask DisposeAsync()
/// <inheritdoc/>
public async Task SendMessageAsync(IJsonRpcMessage message, CancellationToken cancellationToken = default)
{
if (_sseWriteTask is null)
if (!IsConnected)
{
throw new InvalidOperationException($"Transport is not connected. Make sure to call {nameof(RunAsync)} first.");
}
Expand All @@ -80,7 +83,7 @@ public async Task SendMessageAsync(IJsonRpcMessage message, CancellationToken ca
/// <exception cref="InvalidOperationException">Thrown when there is an attempt to process a message before calling <see cref="RunAsync(CancellationToken)"/>.</exception>
public async Task OnMessageReceivedAsync(IJsonRpcMessage message, CancellationToken cancellationToken)
{
if (_sseWriteTask is null)
if (!IsConnected)
{
throw new InvalidOperationException($"Transport is not connected. Make sure to call {nameof(RunAsync)} first.");
}
Expand Down