Module: JsonRpcHandler

Extended by:
JsonRpcHandler
Included in:
JsonRpcHandler
Defined in:
lib/json_rpc_handler.rb

Defined Under Namespace

Classes: ErrorCode, Version

Constant Summary collapse

DEFAULT_ALLOWED_ID_CHARACTERS = 
/\A[a-zA-Z0-9_-]+\z/
NO_RESPONSE =

Sentinel return value from a handler. When a handler returns this, process_request emits no JSON-RPC response for the request, matching the notification-style semantics (id is ignored).

Object.new.freeze

Instance Method Summary collapse

Instance Method Details

#error_response(id:, id_validation_pattern:, error:) ⇒ Object 



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# File 'lib/json_rpc_handler.rb', line 199

def error_response(id:, id_validation_pattern:, error:)
  {
    jsonrpc: Version::V2_0,
    id: valid_id?(id, id_validation_pattern) ? id : nil,
    error: error.compact,
  } unless id.nil?
end

#handle(request, id_validation_pattern: DEFAULT_ALLOWED_ID_CHARACTERS, &method_finder) ⇒ Object 



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# File 'lib/json_rpc_handler.rb', line 28

def handle(request, id_validation_pattern: DEFAULT_ALLOWED_ID_CHARACTERS, &method_finder)
  if request.is_a?(Array)
    return error_response(id: :unknown_id, id_validation_pattern: id_validation_pattern, error: {
      code: ErrorCode::INVALID_REQUEST,
      message: "Invalid Request",
      data: "Request is an empty array",
    }) if request.empty?

    # Handle batch requests
    responses = request.map { |req| process_request(req, id_validation_pattern: id_validation_pattern, &method_finder) }.compact

    # A single item is hoisted out of the array
    return responses.first if responses.one?

    # An empty array yields nil
    responses if responses.any?
  elsif request.is_a?(Hash)
    # Handle single request
    process_request(request, id_validation_pattern: id_validation_pattern, &method_finder)
  else
    error_response(id: :unknown_id, id_validation_pattern: id_validation_pattern, error: {
      code: ErrorCode::INVALID_REQUEST,
      message: "Invalid Request",
      data: "Request must be an array or a hash",
    })
  end
end

#handle_json(request_json, id_validation_pattern: DEFAULT_ALLOWED_ID_CHARACTERS, &method_finder) ⇒ Object 



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# File 'lib/json_rpc_handler.rb', line 56

def handle_json(request_json, id_validation_pattern: DEFAULT_ALLOWED_ID_CHARACTERS, &method_finder)
  begin
    request = JSON.parse(request_json, symbolize_names: true)
    response = handle(request, id_validation_pattern: id_validation_pattern, &method_finder)
  rescue JSON::ParserError
    response = error_response(id: :unknown_id, id_validation_pattern: id_validation_pattern, error: {
      code: ErrorCode::PARSE_ERROR,
      message: "Parse error",
      data: "Invalid JSON",
    })
  rescue StandardError
    # Last-resort guard so an unexpected handling error returns a JSON-RPC error
    # instead of escaping to the transport loop.
    response = error_response(id: :unknown_id, id_validation_pattern: id_validation_pattern, error: {
      code: ErrorCode::INTERNAL_ERROR,
      message: "Internal error",
    })
  end

  response&.to_json
end

#handle_request_error(error, id, id_validation_pattern) ⇒ Object 



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# File 'lib/json_rpc_handler.rb', line 147

def handle_request_error(error, id, id_validation_pattern)
  if error.respond_to?(:error_code) && error.error_code
    code = error.error_code
    message = error.message
  else
    error_type = error.respond_to?(:error_type) ? error.error_type : nil

    code, message = case error_type
    when :invalid_request then [ErrorCode::INVALID_REQUEST, "Invalid Request"]
    when :invalid_params then [ErrorCode::INVALID_PARAMS, "Invalid params"]
    when :parse_error then [ErrorCode::PARSE_ERROR, "Parse error"]
    when :internal_error then [ErrorCode::INTERNAL_ERROR, "Internal error"]
    else [ErrorCode::INTERNAL_ERROR, "Internal error"]
    end
  end

  data = error.respond_to?(:error_data) && error.error_data ? error.error_data : error.message

  error_response(id: id, id_validation_pattern: id_validation_pattern, error: {
    code: code,
    message: message,
    data: data,
  })
end

#process_request(request, id_validation_pattern:, &method_finder) ⇒ Object 



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# File 'lib/json_rpc_handler.rb', line 78

def process_request(request, id_validation_pattern:, &method_finder)
  # A batch element can be any JSON value; a non-object element cannot carry an id or a method,
  # so reject it before the `request[:id]` access below.
  unless request.is_a?(Hash)
    return error_response(id: :unknown_id, id_validation_pattern: id_validation_pattern, error: {
      code: ErrorCode::INVALID_REQUEST,
      message: "Invalid Request",
      data: "Request must be an object",
    })
  end

  id = request[:id]

  error = if !valid_version?(request[:jsonrpc])
    "JSON-RPC version must be 2.0"
  elsif !valid_id?(id, id_validation_pattern)
    "Request ID must match validation pattern, or be an integer or null"
  elsif !valid_method_name?(request[:method])
    'Method name must be a string and not start with "rpc."'
  end

  # Per JSON-RPC 2.0 (Response object, `id`), the error response must carry
  # the same id as the request when the id could be detected; null is only
  # for requests whose id could not be determined. `error_response` nils out
  # ids that fail validation, and the `:unknown_id` sentinel keeps a response
  # (with a null id) being emitted when the request carried no id at all.
  return error_response(id: id.nil? ? :unknown_id : id, id_validation_pattern: id_validation_pattern, error: {
    code: ErrorCode::INVALID_REQUEST,
    message: "Invalid Request",
    data: error,
  }) if error

  method_name = request[:method]
  params = request[:params]

  unless valid_params?(params)
    return error_response(id: id, id_validation_pattern: id_validation_pattern, error: {
      code: ErrorCode::INVALID_PARAMS,
      message: "Invalid params",
      data: "Method parameters must be an array or an object or null",
    })
  end

  begin
    method = method_finder.call(method_name, id)

    if method.nil?
      return error_response(id: id, id_validation_pattern: id_validation_pattern, error: {
        code: ErrorCode::METHOD_NOT_FOUND,
        message: "Method not found",
        data: method_name,
      })
    end

    result = method.call(params)
    return if result.equal?(NO_RESPONSE)

    success_response(id: id, result: result)
  rescue MCP::Server::RequestHandlerError => e
    handle_request_error(e, id, id_validation_pattern)
  rescue StandardError => e
    error_response(id: id, id_validation_pattern: id_validation_pattern, error: {
      code: ErrorCode::INTERNAL_ERROR,
      message: "Internal error",
      data: e.message,
    })
  end
end

#success_response(id:, result:) ⇒ Object 



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# File 'lib/json_rpc_handler.rb', line 191

def success_response(id:, result:)
  {
    jsonrpc: Version::V2_0,
    id: id,
    result: result,
  } unless id.nil?
end

#valid_id?(id, pattern = nil) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/json_rpc_handler.rb', line 176

def valid_id?(id, pattern = nil)
  return true if id.nil? || id.is_a?(Integer)
  return false unless id.is_a?(String)

  pattern ? id.match?(pattern) : true
end

#valid_method_name?(method) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/json_rpc_handler.rb', line 183

def valid_method_name?(method)
  method.is_a?(String) && !method.start_with?("rpc.")
end

#valid_params?(params) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/json_rpc_handler.rb', line 187

def valid_params?(params)
  params.nil? || params.is_a?(Array) || params.is_a?(Hash)
end

#valid_version?(version) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/json_rpc_handler.rb', line 172

def valid_version?(version)
  version == Version::V2_0
end