6d42cf7826
## Motivation and Context A JSON-RPC notification carries no id and must not receive any response. When a client erroneously sent a notification-only method such as `notifications/cancelled` with an id, the server replied with a successful `result: null`, which is neither a valid MCP result nor a legal reply to a notification. Such a message is now treated as a request for a method that has no request handler and rejected with Method not found, matching the behavior of the TypeScript and Python SDKs. A well-formed notification that omits the id continues to receive no response. Fixes #434. ## How Has This Been Tested? Added regression tests covering id-bearing `notifications/cancelled`, `notifications/initialized`, and `notifications/progress`, a batch that mixes an id-bearing notification with other messages, custom `notifications/*` methods, and the same case over the HTTP transport. ## Breaking Changes None for spec-conformant clients, which never put an id on a notification. The only behavioral change is that a malformed id-bearing notification now receives a Method not found error instead of a spurious `result: null`.
101 lines
4 KiB
Ruby
101 lines
4 KiB
Ruby
# frozen_string_literal: true
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module MCP
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module Methods
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INITIALIZE = "initialize"
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PING = "ping"
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LOGGING_SET_LEVEL = "logging/setLevel"
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PROMPTS_GET = "prompts/get"
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PROMPTS_LIST = "prompts/list"
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COMPLETION_COMPLETE = "completion/complete"
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RESOURCES_LIST = "resources/list"
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RESOURCES_READ = "resources/read"
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RESOURCES_TEMPLATES_LIST = "resources/templates/list"
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RESOURCES_SUBSCRIBE = "resources/subscribe"
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RESOURCES_UNSUBSCRIBE = "resources/unsubscribe"
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TOOLS_CALL = "tools/call"
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TOOLS_LIST = "tools/list"
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ROOTS_LIST = "roots/list"
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SAMPLING_CREATE_MESSAGE = "sampling/createMessage"
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ELICITATION_CREATE = "elicitation/create"
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# Notification methods
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NOTIFICATIONS_INITIALIZED = "notifications/initialized"
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NOTIFICATIONS_TOOLS_LIST_CHANGED = "notifications/tools/list_changed"
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NOTIFICATIONS_PROMPTS_LIST_CHANGED = "notifications/prompts/list_changed"
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NOTIFICATIONS_RESOURCES_LIST_CHANGED = "notifications/resources/list_changed"
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NOTIFICATIONS_RESOURCES_UPDATED = "notifications/resources/updated"
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NOTIFICATIONS_ROOTS_LIST_CHANGED = "notifications/roots/list_changed"
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NOTIFICATIONS_MESSAGE = "notifications/message"
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NOTIFICATIONS_PROGRESS = "notifications/progress"
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NOTIFICATIONS_CANCELLED = "notifications/cancelled"
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NOTIFICATIONS_ELICITATION_COMPLETE = "notifications/elicitation/complete"
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class MissingRequiredCapabilityError < StandardError
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attr_reader :method
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attr_reader :capability
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def initialize(method, capability)
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super("Server does not support #{capability} (required for #{method})")
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@method = method
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@capability = capability
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end
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end
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class << self
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def notification?(method)
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method.is_a?(String) && method.start_with?("notifications/")
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end
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def ensure_capability!(method, capabilities)
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case method
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when PROMPTS_GET, PROMPTS_LIST
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require_capability!(method, capabilities, :prompts)
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when NOTIFICATIONS_PROMPTS_LIST_CHANGED
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require_capability!(method, capabilities, :prompts)
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require_capability!(method, capabilities, :prompts, :listChanged)
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when RESOURCES_LIST, RESOURCES_TEMPLATES_LIST, RESOURCES_READ
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require_capability!(method, capabilities, :resources)
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when NOTIFICATIONS_RESOURCES_LIST_CHANGED
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require_capability!(method, capabilities, :resources)
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require_capability!(method, capabilities, :resources, :listChanged)
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when RESOURCES_SUBSCRIBE, RESOURCES_UNSUBSCRIBE, NOTIFICATIONS_RESOURCES_UPDATED
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require_capability!(method, capabilities, :resources)
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require_capability!(method, capabilities, :resources, :subscribe)
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when TOOLS_CALL, TOOLS_LIST
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require_capability!(method, capabilities, :tools)
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when NOTIFICATIONS_TOOLS_LIST_CHANGED
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require_capability!(method, capabilities, :tools)
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require_capability!(method, capabilities, :tools, :listChanged)
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when LOGGING_SET_LEVEL, NOTIFICATIONS_MESSAGE
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require_capability!(method, capabilities, :logging)
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when COMPLETION_COMPLETE
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require_capability!(method, capabilities, :completions)
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when ROOTS_LIST
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require_capability!(method, capabilities, :roots)
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when SAMPLING_CREATE_MESSAGE
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require_capability!(method, capabilities, :sampling)
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when ELICITATION_CREATE
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require_capability!(method, capabilities, :elicitation)
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when INITIALIZE, PING, NOTIFICATIONS_INITIALIZED, NOTIFICATIONS_ROOTS_LIST_CHANGED,
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NOTIFICATIONS_PROGRESS, NOTIFICATIONS_CANCELLED, NOTIFICATIONS_ELICITATION_COMPLETE
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# No specific capability required.
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end
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end
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private
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def require_capability!(method, capabilities, *keys)
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name = keys.join(".") # :resources, :subscribe -> "resources.subscribe"
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has_capability = capabilities.dig(*keys)
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return if has_capability
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raise MissingRequiredCapabilityError.new(method, name)
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end
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end
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end
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end
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