from typing import Any, Literal import pytest import mcp.types as types from mcp.shared.memory import ( create_connected_server_and_client_session as create_session, ) from mcp.shared.session import RequestResponder from mcp.types import ( LoggingMessageNotificationParams, TextContent, ) class LoggingCollector: def __init__(self): self.log_messages: list[LoggingMessageNotificationParams] = [] async def __call__(self, params: LoggingMessageNotificationParams) -> None: self.log_messages.append(params) @pytest.mark.anyio async def test_logging_callback(): from mcp.server.fastmcp import FastMCP server = FastMCP("test") logging_collector = LoggingCollector() # Create a simple test tool @server.tool("test_tool") async def test_tool() -> bool: # The actual tool is very simple and just returns True return True # Create a function that can send a log notification @server.tool("test_tool_with_log") async def test_tool_with_log( message: str, level: Literal["debug", "info", "warning", "error"], logger: str ) -> bool: """Send a log notification to the client.""" await server.get_context().log( level=level, message=message, logger_name=logger, ) return True @server.tool("test_tool_with_log_extra") async def test_tool_with_log_extra( message: str, level: Literal["debug", "info", "warning", "error"], logger: str, extra_string: str, extra_dict: dict[str, Any], ) -> bool: """Send a log notification to the client with extra fields.""" await server.get_context().log( level=level, message=message, logger_name=logger, extra={"extra_string": extra_string, "extra_dict": extra_dict}, ) return True # Create a message handler to catch exceptions async def message_handler( message: RequestResponder[types.ServerRequest, types.ClientResult] | types.ServerNotification | Exception, ) -> None: if isinstance(message, Exception): # pragma: no cover raise message async with create_session( server._mcp_server, logging_callback=logging_collector, message_handler=message_handler, ) as client_session: # First verify our test tool works result = await client_session.call_tool("test_tool", {}) assert result.isError is False assert isinstance(result.content[0], TextContent) assert result.content[0].text == "true" # Now send a log message via our tool log_result = await client_session.call_tool( "test_tool_with_log", { "message": "Test log message", "level": "info", "logger": "test_logger", }, ) log_result_with_extra = await client_session.call_tool( "test_tool_with_log_extra", { "message": "Test log message", "level": "info", "logger": "test_logger", "extra_string": "example", "extra_dict": {"a": 1, "b": 2, "c": 3}, }, ) assert log_result.isError is False assert log_result_with_extra.isError is False assert len(logging_collector.log_messages) == 2 # Create meta object with related_request_id added dynamically log = logging_collector.log_messages[0] assert log.level == "info" assert log.logger == "test_logger" assert log.data == "Test log message" log_with_extra = logging_collector.log_messages[1] assert log_with_extra.level == "info" assert log_with_extra.logger == "test_logger" assert log_with_extra.data == { "message": "Test log message", "extra_string": "example", "extra_dict": {"a": 1, "b": 2, "c": 3}, }