eeb130171d
## Motivation and Context MCP spec (2025-11-25) defines Roots as a mechanism for clients to expose filesystem boundaries (directories and files) to servers: https://modelcontextprotocol.io/specification/2025-11-25/client/roots This enables servers to understand which parts of the filesystem they can operate on. This adds support for the two roots protocol interactions: - `roots/list` -- server-to-client request to retrieve the client's filesystem roots - `notifications/roots/list_changed` -- client-to-server notification when roots change `roots/list` is a one-to-one request between a server and a specific client, so `list_roots` is exposed only at the session level (`ServerSession#list_roots`), matching the Python SDK approach and aligning with PR #311 for sampling. `Server#on_roots_list_changed` registers a callback for the client notification, which is server-wide and does not require session scoping. Also fixes `notifications/roots/list_changed` capability checking: as a client-originated notification, it should not require server-side capability declaration. ## How Has This Been Tested? New test file `test/mcp/server_roots_test.rb` with 8 test cases covering session-scoped `list_roots`, capability validation and fallback, `on_roots_list_changed` callback registration, and client capability storage. Updated `test/mcp/methods_test.rb` to reflect the corrected capability checks. All tests pass (`rake test`), RuboCop is clean. ## Breaking Changes None.
97 lines
3.9 KiB
Ruby
97 lines
3.9 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 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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