7dcba357d4- Changes IJsonRpcMessage to an abstract base class so RelatedTransport will always be available - Streamable HTTP supports multiple concurrent HTTP request with their own indpendent SSE response streams - RelatedTransport indicates the source or destination of the JsonRpcMessage - Changes the default RequestId to a JSON number for better compatibility with MCP servers in the wild
110 lines
No EOL
4.5 KiB
C#
110 lines
No EOL
4.5 KiB
C#
using ModelContextProtocol.Protocol.Messages;
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using System.ComponentModel;
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using System.Text.Json;
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using System.Text.Json.Serialization;
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namespace ModelContextProtocol.Utils.Json;
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/// <summary>
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/// Provides a <see cref="JsonConverter"/> for <see cref="JsonRpcMessage"/> messages,
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/// handling polymorphic deserialization of different message types.
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/// </summary>
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/// <remarks>
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/// <para>
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/// This converter is responsible for correctly deserializing JSON-RPC messages into their appropriate
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/// concrete types based on the message structure. It analyzes the JSON payload and determines if it
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/// represents a request, notification, successful response, or error response.
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/// </para>
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/// <para>
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/// The type determination rules follow the JSON-RPC 2.0 specification:
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/// <list type="bullet">
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/// <item><description>Messages with "method" and "id" properties are deserialized as <see cref="JsonRpcRequest"/>.</description></item>
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/// <item><description>Messages with "method" but no "id" property are deserialized as <see cref="JsonRpcNotification"/>.</description></item>
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/// <item><description>Messages with "id" and "result" properties are deserialized as <see cref="JsonRpcResponse"/>.</description></item>
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/// <item><description>Messages with "id" and "error" properties are deserialized as <see cref="JsonRpcError"/>.</description></item>
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/// </list>
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/// </para>
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/// </remarks>
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[EditorBrowsable(EditorBrowsableState.Never)]
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public sealed class JsonRpcMessageConverter : JsonConverter<JsonRpcMessage>
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{
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/// <inheritdoc/>
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public override JsonRpcMessage? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
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{
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if (reader.TokenType != JsonTokenType.StartObject)
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{
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throw new JsonException("Expected StartObject token");
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}
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using var doc = JsonDocument.ParseValue(ref reader);
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var root = doc.RootElement;
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// All JSON-RPC messages must have a jsonrpc property with value "2.0"
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if (!root.TryGetProperty("jsonrpc", out var versionProperty) ||
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versionProperty.GetString() != "2.0")
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{
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throw new JsonException("Invalid or missing jsonrpc version");
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}
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// Determine the message type based on the presence of id, method, and error properties
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bool hasId = root.TryGetProperty("id", out _);
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bool hasMethod = root.TryGetProperty("method", out _);
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bool hasError = root.TryGetProperty("error", out _);
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var rawText = root.GetRawText();
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// Messages with an id but no method are responses
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if (hasId && !hasMethod)
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{
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// Messages with an error property are error responses
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if (hasError)
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{
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return JsonSerializer.Deserialize(rawText, options.GetTypeInfo<JsonRpcError>());
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}
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// Messages with a result property are success responses
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if (root.TryGetProperty("result", out _))
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{
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return JsonSerializer.Deserialize(rawText, options.GetTypeInfo<JsonRpcResponse>());
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}
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throw new JsonException("Response must have either result or error");
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}
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// Messages with a method but no id are notifications
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if (hasMethod && !hasId)
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{
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return JsonSerializer.Deserialize(rawText, options.GetTypeInfo<JsonRpcNotification>());
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}
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// Messages with both method and id are requests
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if (hasMethod && hasId)
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{
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return JsonSerializer.Deserialize(rawText, options.GetTypeInfo<JsonRpcRequest>());
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}
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throw new JsonException("Invalid JSON-RPC message format");
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}
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/// <inheritdoc/>
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public override void Write(Utf8JsonWriter writer, JsonRpcMessage value, JsonSerializerOptions options)
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{
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switch (value)
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{
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case JsonRpcRequest request:
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JsonSerializer.Serialize(writer, request, options.GetTypeInfo<JsonRpcRequest>());
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break;
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case JsonRpcNotification notification:
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JsonSerializer.Serialize(writer, notification, options.GetTypeInfo<JsonRpcNotification>());
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break;
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case JsonRpcResponse response:
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JsonSerializer.Serialize(writer, response, options.GetTypeInfo<JsonRpcResponse>());
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break;
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case JsonRpcError error:
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JsonSerializer.Serialize(writer, error, options.GetTypeInfo<JsonRpcError>());
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break;
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default:
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throw new JsonException($"Unknown JSON-RPC message type: {value.GetType()}");
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}
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}
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} |