Hermes-agent

tests/tools/test_mcp_cancelled_error_propagation.py

@@ -0,0 +1,91 @@
+"""Regression tests for ``MCPServerTask.run`` + ``asyncio.CancelledError``.
+
+Background
+==========
+On Python 3.11+, ``asyncio.CancelledError`` inherits from ``BaseException``
+rather than ``Exception``, so a bare ``except Exception`` does NOT catch it.
+``MCPServerTask.run`` had a broad ``except Exception`` around the transport
+loop which meant a task cancellation (gateway restart, explicit
+``task.cancel()``) caused the reconnect loop to exit silently — the MCP
+server stayed dead until Hermes was restarted. See #9930.
+
+The fix adds an explicit ``except asyncio.CancelledError: raise`` BEFORE
+the broad catch so cancellation propagates cleanly to asyncio's task
+machinery and ``MCPServerTask.shutdown()``'s ``await self._task`` completes
+without hanging the reconnect loop.
+"""
+
+from __future__ import annotations
+
+import asyncio
+from unittest.mock import patch
+
+
+
+async def _hanging_run(self, cfg):
+    """Stand-in transport that hangs forever so we can cancel it."""
+    await asyncio.sleep(3600)
+
+
+class TestCancelledErrorPropagation:
+    def test_cancelled_error_is_not_swallowed_by_except_exception(self):
+        """CancelledError raised inside the transport call must re-raise
+        so the reconnect loop terminates cleanly on cancel — not stay wedged."""
+        from tools.mcp_tool import MCPServerTask
+
+        server = MCPServerTask("cancel-test")
+
+        async def drive():
+            with patch.object(MCPServerTask, "_run_stdio", _hanging_run), \
+                 patch.object(MCPServerTask, "_is_http", lambda self: False):
+                task = asyncio.create_task(server.run({"command": "fake"}))
+                # Let the run loop enter the try/except and start awaiting.
+                await asyncio.sleep(0.05)
+                task.cancel()
+                # The fix guarantees the task completes (either via
+                # CancelledError propagation or clean exit) rather than
+                # hanging forever.
+                try:
+                    await asyncio.wait_for(task, timeout=2.0)
+                except asyncio.CancelledError:
+                    return "cancelled_cleanly"
+                except asyncio.TimeoutError:
+                    # If we hit this, the reconnect loop swallowed the cancel
+                    # and stayed wedged — the exact #9930 bug.
+                    task.cancel()
+                    try:
+                        await task
+                    except Exception:
+                        pass
+                    return "wedged"
+                return "clean_return"
+
+        outcome = asyncio.run(drive())
+        assert outcome in {"cancelled_cleanly", "clean_return"}, (
+            f"MCPServerTask.run wedged on cancel (outcome={outcome}) — "
+            f"#9930 regression"
+        )
+
+    def test_shutdown_completes_promptly_when_task_is_cancelled(self):
+        """``shutdown()`` falls through to ``task.cancel()`` + ``await self._task``
+        after a grace period. That cancel must unwedge the reconnect loop —
+        otherwise ``await self._task`` hangs indefinitely."""
+        from tools.mcp_tool import MCPServerTask
+
+        server = MCPServerTask("shutdown-cancel-test")
+
+        async def drive():
+            with patch.object(MCPServerTask, "_run_stdio", _hanging_run), \
+                 patch.object(MCPServerTask, "_is_http", lambda self: False):
+                server._task = asyncio.ensure_future(server.run({"command": "fake"}))
+                await asyncio.sleep(0.05)
+                server._shutdown_event.set()
+                server._task.cancel()
+                try:
+                    await asyncio.wait_for(server._task, timeout=2.0)
+                except (asyncio.CancelledError, asyncio.TimeoutError):
+                    pass
+                return server._task.done()
+
+        done = asyncio.run(drive())
+        assert done, "MCPServerTask did not finish after cancel — #9930 regression"