Guard in-process HTTP tests against sse-starlette's global exit event

sse-starlette <3.0 stores its exit Event on the AppStatus class the first
time an EventSourceResponse runs; the Event is bound to that test's event
loop and breaks every later in-process SSE response on the same worker.
test_http_unicode.py serves all its requests as EventSourceResponses
(json_response=False) but had no reset fixture, so on a sse-starlette<3.0
install (CI's lowest-direct legs) it could poison the worker for any later
SSE-based test.

- Copy the autouse AppStatus reset fixture into test_http_unicode.py.
- Reset on both sides of the yield, here and in test_sse.py, so each
  module also survives a stale Event left behind by an earlier test.
- Correct the filterwarnings comments in both files: the item-scoped
  markers cannot cover the GC flush at session cleanup, so isolated
  runs without xdist (-n 0) still exit nonzero after all tests pass.

Author: maxisbey

tests/client/test_http_unicode.py

@@ -5,12 +5,13 @@
 (server→client and client→server) using the streamable HTTP transport.
 """
 
-from collections.abc import AsyncIterator
+from collections.abc import AsyncIterator, Iterator
 from contextlib import asynccontextmanager
 from typing import Any
 
 import httpx
 import pytest
+from sse_starlette.sse import AppStatus
 from starlette.applications import Starlette
 from starlette.routing import Mount
 
@@ -28,14 +29,40 @@
 # v1's streamable-HTTP server transport leaks a handful of anyio memory streams on teardown when
 # run in process; the old subprocess harness never observed them. The interaction suite registers
 # the same two scoped filters globally from tests/interaction/conftest.py (see the comment there),
-# but they only take effect when that package's conftest is loaded; these markers keep this file
-# self-contained for isolated runs. The filters are scoped to anyio's MemoryObject*Stream leak
-# signature so an unrelated leak still fails the suite.
+# but they only take effect when that package's conftest is loaded; these markers keep the tests
+# themselves passing in isolated runs. Markers are item-scoped, so they cannot cover the GC
+# flush at session cleanup: an isolated run without xdist (`-n 0`) still exits nonzero after all
+# tests pass. The default xdist runs (addopts has `-n auto`) are unaffected, as are full-suite
+# runs, where the interaction conftest's ini-level filters apply. The filters are scoped to
+# anyio's MemoryObject*Stream leak signature so an unrelated leak still fails the suite.
 pytestmark = [
     pytest.mark.filterwarnings("ignore:.*MemoryObject(Send|Receive)Stream:pytest.PytestUnraisableExceptionWarning"),
     pytest.mark.filterwarnings("ignore:.*MemoryObject(Send|Receive)Stream:ResourceWarning"),
 ]
 
+
+@pytest.fixture(autouse=True)
+def _reset_sse_starlette_exit_event() -> Iterator[None]:
+    """Reset sse-starlette's module-global exit Event around each test.
+
+    sse-starlette <3.0 (allowed by this branch's dependency floor; CI's lowest-direct leg
+    installs it) stores an `anyio.Event` on the `AppStatus` class the first time an
+    `EventSourceResponse` runs; that Event is bound to the test's event loop and breaks every
+    subsequent in-process SSE response (and `json_response=False` below means every request
+    in this module is served as one). sse-starlette 3.x switched to a ContextVar and has no
+    such attribute. Resetting on both sides of the test keeps this module immune to a stale
+    Event left behind by an earlier test on the same worker as well as cleaning up after its
+    own. This mirrors the autouse fixtures in tests/shared/test_sse.py and
+    tests/interaction/conftest.py.
+    """
+    if hasattr(AppStatus, "should_exit_event"):  # pragma: no branch
+        # setattr keeps pyright happy: the locked sse-starlette 3.x has no such attribute.
+        setattr(AppStatus, "should_exit_event", None)  # pragma: lax no cover
+    yield
+    if hasattr(AppStatus, "should_exit_event"):  # pragma: no branch
+        setattr(AppStatus, "should_exit_event", None)  # pragma: lax no cover
+
+
 # Test constants with various Unicode characters
 UNICODE_TEST_STRINGS = {
     "cyrillic": "Слой хранилища, где располагаются",

tests/shared/test_sse.py

@@ -49,9 +49,12 @@
 # v1's HTTP server transports leak a handful of anyio memory streams on teardown when run in
 # process; the old subprocess harness never observed them. The interaction suite registers the
 # same two scoped filters globally from tests/interaction/conftest.py (see the comment there),
-# but they only take effect when that package's conftest is loaded; these markers keep this file
-# self-contained for isolated runs. The filters are scoped to anyio's MemoryObject*Stream leak
-# signature so an unrelated leak still fails the suite.
+# but they only take effect when that package's conftest is loaded; these markers keep the tests
+# themselves passing in isolated runs. Markers are item-scoped, so they cannot cover the GC
+# flush at session cleanup: an isolated run without xdist (`-n 0`) still exits nonzero after all
+# tests pass. The default xdist runs (addopts has `-n auto`) are unaffected, as are full-suite
+# runs, where the interaction conftest's ini-level filters apply. The filters are scoped to
+# anyio's MemoryObject*Stream leak signature so an unrelated leak still fails the suite.
 pytestmark = [
     pytest.mark.filterwarnings("ignore:.*MemoryObject(Send|Receive)Stream:pytest.PytestUnraisableExceptionWarning"),
     pytest.mark.filterwarnings("ignore:.*MemoryObject(Send|Receive)Stream:ResourceWarning"),
@@ -60,19 +63,23 @@
 
 @pytest.fixture(autouse=True)
 def _reset_sse_starlette_exit_event() -> Iterator[None]:
-    """Reset sse-starlette's module-global exit Event after each test.
+    """Reset sse-starlette's module-global exit Event around each test.
 
     sse-starlette <3.0 (allowed by this branch's dependency floor; CI's lowest-direct leg
     installs it) stores an `anyio.Event` on the `AppStatus` class the first time an
     `EventSourceResponse` runs; that Event is bound to the test's event loop and breaks every
     subsequent in-process SSE response. sse-starlette 3.x switched to a ContextVar and has no
-    such attribute. This mirrors the autouse fixture in tests/interaction/conftest.py, which
-    guards the interaction suite the same way.
+    such attribute. Resetting on both sides of the test keeps this module immune to a stale
+    Event left behind by an earlier test on the same worker as well as cleaning up after its
+    own. This mirrors the autouse fixture in tests/interaction/conftest.py, which guards the
+    interaction suite the same way.
     """
-    yield
     if hasattr(AppStatus, "should_exit_event"):  # pragma: no branch
         # setattr keeps pyright happy: the locked sse-starlette 3.x has no such attribute.
         setattr(AppStatus, "should_exit_event", None)  # pragma: lax no cover
+    yield
+    if hasattr(AppStatus, "should_exit_event"):  # pragma: no branch
+        setattr(AppStatus, "should_exit_event", None)  # pragma: lax no cover
 
 
 def in_process_client_factory(app: Starlette) -> McpHttpClientFactory: