fix: add BaseExceptionGroup compat import for Python 3.10 + ruff format

Author: g97iulio1609

src/mcp/shared/_exception_utils.py

@@ -7,12 +7,16 @@
 
 from __future__ import annotations
 
+import sys
 from collections.abc import AsyncIterator
 from contextlib import asynccontextmanager
 
 import anyio
 from anyio.abc import TaskGroup
 
+if sys.version_info < (3, 11):
+    from exceptiongroup import BaseExceptionGroup
+
 
 def collapse_exception_group(exc_group: BaseExceptionGroup[BaseException]) -> BaseException:
     """Collapse a single-error exception group into the underlying exception.
@@ -31,9 +35,7 @@ def collapse_exception_group(exc_group: BaseExceptionGroup[BaseException]) -> Ba
         otherwise the original exception group unchanged.
     """
     cancelled_class = anyio.get_cancelled_exc_class()
-    real_errors: list[BaseException] = [
-        exc for exc in exc_group.exceptions if not isinstance(exc, cancelled_class)
-    ]
+    real_errors: list[BaseException] = [exc for exc in exc_group.exceptions if not isinstance(exc, cancelled_class)]
 
     if len(real_errors) == 1:
         return real_errors[0]

tests/shared/test_exception_utils.py

@@ -1,9 +1,14 @@
 """Tests for exception group collapsing utilities."""
 
+import sys
+
 import pytest
 
 import anyio
 
+if sys.version_info < (3, 11):
+    from exceptiongroup import BaseExceptionGroup
+
 from mcp.shared._exception_utils import collapse_exception_group, create_task_group
 
 
@@ -57,9 +62,7 @@ async def test_multiple_cancelled_one_real(self) -> None:
         cancelled_class = anyio.get_cancelled_exc_class()
         real_error = ConnectionError("lost connection")
 
-        group = BaseExceptionGroup(
-            "test", [cancelled_class(), real_error, cancelled_class()]
-        )
+        group = BaseExceptionGroup("test", [cancelled_class(), real_error, cancelled_class()])
         result = collapse_exception_group(group)
 
         assert result is real_error