fix:Improve code maintainability: Add a public mcp_server attribute to FastMCP, implement RootsListChangedNotification handling, simplify capability check logic, and optimize the use of the TRANSPORTS variable

Author: xy200303

src/mcp/server/fastmcp/server.py

@@ -213,11 +213,11 @@ def session_manager(self) -> StreamableHTTPSessionManager:
             RuntimeError: If called before streamable_http_app() has been called.
         """
         return self._mcp_server.session_manager  # pragma: no cover
-    
+
     @property
     def mcp_server(self):
         """Get the underlying MCP server instance.
-        
+
         This is exposed to enable advanced use cases like in-memory testing.
         """
         return self._mcp_server

src/mcp/server/session.py

@@ -147,7 +147,7 @@ def check_client_capability(self, capability: types.ClientCapabilities) -> bool:
         # Check sampling capability
         if capability.sampling and not client_caps.sampling:  # pragma: lax no cover
             return False
-        if capability.sampling:  # pragma: lax no cover
+        if capability.sampling and client_caps.sampling:  # pragma: lax no cover
             if capability.sampling.context and not client_caps.sampling.context:  # pragma: lax no cover
                 return False
             if capability.sampling.tools and not client_caps.sampling.tools:  # pragma: lax no cover